An Ecological Study of Bush Stone-curlews Burhi grallarius onKangaroo Island, South Australia
Master of Science l)egree Department of Environmental Biolo gy Adelaide University
Jody A. Gates 2001 Preface
This thesis has been prepared in order to fulfil the requirements of the Degree of Master of
Science by research, with the Department of Environmental Biology, at Adelaide University'
This thesis contains no material which has been accepted for the award of any other degree or diploma in any university or tertiary institution, and to the best of my knowledge and belief, the thesis contains no material previously published or written by another person, except where due reference is made in the text of the thesis.
I give consent to this copy of my thesis, when deposited in the University Llbtary, being available for loan and photocopying.
Signed: 2s-L-oZ A Date
ll Acknowledsments The majority of the field research for this project was undertaken whilst I was working full- time as a Senior Ranger at Flinders Chase National Park on Kangaroo Island, between 1995 and 1998. This put considerable time constraints on f,reldwork timetables, however, National
Parks and Wildlife, South Australia were supportive of the project and provided study leave to assist with undertaking fieldwork. The thesis was subsequently prepared between 1998 and 2001, when I was also predominantly employed full-time on various contracts with National Parks and Wildlife SA.
The project was essentially self-funded, however, the generous support of my supervisor Dr David C. Paton is gratefully acknowledged. The NPWSA Wildlife Conservation Fund also provided a grant to cover some expenses associated with the radio-tracking component of the study.
As indicated the project was supervised by Dr. David Paton. Throughout the extended period over which this project was completed David's assistance, encouragement and critical comments were of great value. Thanks Dave!
I would especially like to thank two people for their . considerable assistance during the fieldwork component of this project - Ange Paltridge and Lynn Pedler. Ange assisted with the distribution survey, nest searches, catching and radio-tracking of the birds, and her company and support was greatly appreciated. Lynn was invaluable in assisting with catching the birds and radio-tracking several birds on occasions. His experience with handling birds and general knowledge on ornithology ensured that our catching trips were successful and enjoyable.
The following landholders allowed regular access to their properties (at all hours of the day
and night!)¡for fieldwork: Joe Riggs (lessee of KB Downs), and the following two managers of what is now Hanson Bay Sanctuary, Snow Dennis and Peter Davis.
Gavin Burgess, alias Kevin Bargass, provided guidance and instruction with GIS, and helped
me become proficient enough to eventually produce the maps/f,rgures.
Keith'Walker and Graeme Moss assisted me with the data analysis, partrcularly in Chapters 4
and 5.
111 Helen Richards is thanked for distributing questionnaires through the Landcare Newsletter that she produces for Kangaroo Island.
Wendy and Bob Furner and Fiona Gill provided great hospitality during the latter stages of fieldwork when I no longer lived on the island.
Kinily Blaylock was kind enough to assist with identifying the fragments of invertebrates in the faeces of bush stone-curlews
Kylie Moritz and Steve Gates assisted with the task of proof-reading the final drafts of the thesis
Finally, a special thanks to Mum and Dad whose love of the outdoors led to the development of my interest in birds at r very young age, and led me to pursue a careeÍ in natural resource management. Now I get paid to do the things I've always loved - thanks guys.
IV Abstract Bush stone-curlews Burhinus grallarius forage, roost and nest on the gtound, making them particularly vulnerable to decline. Although once common and widespread throughout southern, eastern and northern Australia, only sporadic records occur across much of their former range in southem and eastern Australia following a major contraction in range (Marchant and Higgins 1993). Two main factors have been implicated in the decline of this species in southern and eastem Australia - predation by foxes and habitat clearance and modification (Marchant and Higgins 1993, Johnson and Baker- Gabb 1994, Saunders and Ingram 1995, Robinson and Traill 1996). Bush stone-curlews have recently been listed as near threatened at the national level (Garnett and Crowley 2000) but have been down- graded from endangered to vulnerable in South Australia, primarily as a result of the findings in this
study.
In contrast to the mainland, bush stone-curlews were apparently common on Kangaroo Island, providing an opporlunity to study their ecology in a temperate environment' The studies were Park undertaken at two major study sites in the south-west of the island: Flinders Chase National Headquarters (FCHQ)and an agricultural property, 'KB Downs'. The objectives of the study were:
in 1. To document the historical distribution, and subsequent decline, of bush stone-curlews South Australia. 2. To determine the current distribution and status of bush stone-curlews on Kangaroo Island. Island' 3. To determine the home range sizes and movements of bush stone-curlews on Kangaroo 4. To determine the characteristics of foraging habitat, day roost areas and nest sites, and the availability of this habitat across Kangaroo Island' 5. To determine the diet and food resources of the bush stone-curlews on Kangaroo Island. 6. To determine potential threats to the population and to make management recommendations aimed at ameliorating these threats'
the late 1880s A total of 414 records of bush stone-curlews were obtained for South Australia from through to 1995. Early records were widespread across the State. However, by 1940 a major decline was evident. By i980 most records came from Kangaroo Island, with relatively few from the Riverland, South-east, Lower Lakes and Southern Eyre Peninsula'
Call-playback surveys were undertaken across Kangaroo Island in 1995196 to determine the current distribution of the birds. Surveys and questionnaires were undeftaken by landholders to compliment sites' the call-playback surveys. The birds were recorded at 109 of 147 (74%) call play-back survey Of the 38 sites where the birds were absent only seven sites (5% of the total) were within agricultural areas, and the remaining 31 sites (21% of the total) occurred within large continuous areas of vegetation, such as Flinders Chase National Park. Combined with the results of questionnaires and
V landholder surveys the call-playback surveys showed that the birds were widespread and common across Kangaroo Island, and showed a strong preference for the agricultural areas. This confirmed that Kangaroo Island was the major stronghold for these birds in southern and eastern Australia.
Fifteen bush stone-curlews were fitted with radio-transmitters between July 1996 and June 1998. Adult birds were preferentially selected, although one juvenile was also radio-tagged. Based on home range sizes and use, three groups of birds were identified: (1) resident breeding birds; (2) mobile breeding and non-breeding birds and (3) fîrst year juveniles. Six birds belonged to group (1) and home range estimates for four of these ranged between 26 ha and 64 ha. These birds regularly used the same sites for roosting, were always observed roosting with another bird, and were recorded breeding within the vicinity of their regular roost sites. Nine birds belonged to the second group, and these birds ranged widely and regularly made long distance movements, which accounted for larger home range sizes of between 120 ha and 817 ha. Five of these birds were recorded using a communal roost with up to 15+ other birds during the non-breeding season, and four ofthese birds subsequently disappeared from the study site. Forlunately one of these birds was subsequently rediscovered eight kilometres away from the study site, suggesting that the birds may have dispersed. The radio-taggedjuvenile was placed within a separate group of birds. This bird remained within the home range of its parents until at least the beginning of the following breeding season. Unforlunately the transmitter either failed or the bird dispersed at this time.
Characteristics of roost, nest and foraging locations were investigated. Roost and nest sites were located through radio-tracking and intensive searching, and foraging locations were obtained from radio-tracking alone. Within three broad habitat types (A- natural vegetation; B- semi- cleared/regrowth vegetation; and C- cleared areas) roost sites @:a7) were predominantly located within vegetation (60% in A, 30o/o in B, 10% in C. Nest sites (n:27) however, were found in cleared landmore oflen(4I,/oin A, l5o/oinB,44Vo in C), and foraging locations (n:819) were primarily in cleared areas (2lo/oin A, l2Yo inB, 670/o in C). The small percentage of records of foraging in natural vegetation, and roosting in cleared areas, were primarily related to nest or chick attendance by the birds. Specific data on vegetation and other habitat variables were collected for all roost and nest sites twere and associated random sites. Multi-dimensional scaling and ordination plots showed that there no differences between the sites used by the birds and the random sites. These results suggest that suitable habitat was abundant on Kangaroo Island, and that land clearance has benefited these birds by opening up otherwise unsuitable habitat.
Faecal analysis and micro-pitfall traps were used to investigate diet and food resources. Faeces (n:a16) were collected opportunistically from roost sites at the two major study sites (FCHQ and 'KB Downs') and one other property ('Brookland Park') between 1995 and 1998. A total of eight micro- pitfall trap sites (each with nine pitfalls) was established at the major study sites. Beetles were the
v1 most coÍrmonly recorded food item (in 90/o of all faeces) followed by spiders, larvaelcatetpillars and ants. Earwigs, centipedes/millipedes, moths, snails and vertebrates were also important food items, but occurred in less than 25%o of faeces. Over 20,000 macro-invertebrates 'were captured in the micro- pitfall traps, and remains of all major groups captured were present in faeces, except for worms. At both of the major study sites beetles and ants accounted for the majority of the captures in the pitfall traps, Seasonal variation in diet was evident, and based on the captures in pitfall traps, primarily reflected changes in the abundance/activity of prey groups. The results demonstrated that the birds were opportunistic foragers with a generalist diet, consuming what was most readily available, with no major preferences observed. All food items had been recorded in other studies. This study suggests that food resources were not likely to be limiting. However, potential changes to the agricultural landscape may have both long and short-term impacts on prey resources, either directly or as a result of changes to foraging habitat.
This study has provided a basis for management and research recommendations for bush stone-curlews to ensure that Kangaroo Island remains a stronghold for the species. The major threats to the birds, habitat clearance and modification, and predation by foxes, are both absent on Kangaroo Island. The initial clearance of native vegetation for agriculture on the Island has actually provided more suitable habitat, as large areas of natural vegetation of minimal value to the birds were cleared and replaced with pasture. However, ongoing changes across the agricultural landscape may be detrimental to the birds, particularly as large areas of potential foraging habitat are being converted to agro-forestry'
vr1 TABLE OF CONTENTS
Preface Acknowledgements Abstract List of Figures...... ,xll List of Tables ...... xiv
CHAPTER 1
INTRODUCTION AND BACKGROUND INFORMATION 1
1.0 Introduction...... 1 l. 1 Background Information...... 3 l. l. I Description .....3 1.1.2 Distribution ...... 4 1.1.3 Habitat .....4 L.I.4 SocialOrganisation .....5 1.1.5 Diet .....7 1.1.6 Vocalisations...... 1 1.1.7 Breedingbiology...... 8
I . I .8 The decline of woodland birds on the mainland .....8 1.2 Aims and Objectives of the Study .....9 1.3 The Study Sites...... 9 1.3.1 Kangaroo Island - A General Overview...... 9 1.3.2 Flinders Chase National Park Headquarters.. ... 11 1.3.3 KB Downs ... t4 1.4 Structure of the Thesis ... l6 CHAPTER 2 THE HISTOzuCAL AND CURRENT DISTRIBUTION OF BUSH STONE- CURLEWS, BUKHINUS GRALLARIUS,IN SOUTH AUSTRALIA AND ON KANGAROO ISLAND. t7 2.0 Introduction...... l1 2.I Methods l8 2.1.1 Historical and current distribution across South Australia. l8 2.1.2 The Kangaroo Island survey l9 2.1.3 Data storage and analysis.... 22 2.2 Results 22 2.2.I Historical and recent records for South Australia...... 22 2.2.2 The Ikngaroo Island survey 22 2.3 Discussion. 30 2.3.1 Effectiveness of survey methodology...... 30 2.3.2 Historicalperspective 31
viii 2.3.3 Distribution on Kangaroo Island and broad habitat preferences 3l 2.3.4 Conclusions...... 33
CHAPTER 3 SIZE OF HOME RANGES AND MOVEMENTS OF BUSH STONE-CURLEV/S BURHINUS GRALLANU,S ON KANGAROO ISLAND 34 3.0 Introduction...... 34 3. I Background Information...... 3s 3.1.1 Definition of home range 35 3.1.2 Analysis of home range sizes 36 3.1.3 Study sites ...... 38 3.2 Methods 40 3.2.I Capturing the birds 40 3.2.2 Radio-transmitter attachment and banding ...... 40 3.2.3 Radio-tracking procedure..,...... 42 3.2.4 Calculation of home range sizes and quantifying movements 43 3.3 Results 44 3.3.I Details of the radio-tracked birds 44 3.3.2 Timing and duration of radio-tracking 46 3.3.3 Comparisons between home range analysis techniques..... 49 3.3.4 Home range sizes and use of home ranges by individual bush stone- curlews 52 3.3.6 The movements of the five birds for which home range estimates could not be determined 67 3.3.1 Summary of patterns of home range size and home range use by the birds 70 3.4 Discussion... 72 3.4.1 Home range sizes and patterns of moverrents of the birds 75 3.4.1 Summary and conclusions 80 CHAPTER 4 CHARACTERISTICS OF ROOST, NEST AND FORAGING SITES SELECTED BY BUSH STONE-CURLEWS BURHINUS GRALLARIUS ON KANGAROO ISLAND. 83 4.0 Introduction...... 83 4.1 Background infonnation on habitat use by bush stone-curlews .84 4.2 Methods .85 4.2.I Locating sites used by the birds ...... 85 4.2.2 Describing macro- and micro-habitats .86 4.2.3 Statistical analysis of nest and roost site data .93 4.3 Results .94 4.3.I Macro-habitat preferences...... 94 4.3.2 Micro-habitat selection...... 96 4.4 Discussion 101 4.4.1 Nest Sites. t02
IX 4.4.1 Characteristics of roost sites...... 103 4.4.3 Foraging (nocturnal) site selection.... 105 4.4.5 Conclusions...... 105
CHAPTER 5 DIET AND FOOD RESOURCES 107 5.0 Introduction...... r07 5.1.1 Other studies on the diet of bush stone-curlews...... 108 5.r.2 Techniques for determining the diet of birds ...... 108 5.1.3 The use of rnicro-pitfalls to assess abundance and diversity of ground- dwelling invertebrates ...... 111 5.2 Methods ...t12 5.2.), Collection and analysis of faeces ...112 5.2.2 Sampling of invertebrates within areas used for foraging by bush stone-curlews lt4 5.2.3 Data analysis rt7 5.3 Results 118 5.3.1 Prey items recorded within faeces...... 118 5.3.2 Potential prey items collected in micro-pitfall traps r24 5.3.3 Comparisons between food groups recorded in faeces and captured in micro-pitfall traps ,...... 130 5.4 Discussion ...... t32 5.4.1 Determination of diet using faecal analysis ...... 132 5 .4.2 Use of micro-pitfall traps to determine potential prey resources ...... 133 5.4.3 The composition of the diet...... r34 5.4.4 Potential prey availability compared with diet...... '.'...... 135 5.4.5 Conclusions...... 138 CHAPTER 6 MANAGEMENT OF BUSH STONE-CURLEWS ON KANGAROO ISLAND AND THE MAINLAND OF SOUTH AUSTRALIA 139 6.1 Introduction...... 139 6.2 Status of bush stone-cur1ews...... ' 139 6.3 Threats to bush stone-cur1ews...... ,...... '...... '."..."" 140 6.3.1 The role of predation by foxes and habitat modification...... 140 6.3.2 Ongoing changes to preferred habitat in Kangaroo Island...... 142 6.3.3 Other threats -.'."'.'142 6.3 Recommendations for further research and management...... 145 6.3.I Recommendations for Kangaroo Island ...146 6.3.2 Recommendations for the South Australian mainland...... 141 6'4 conclusions"""""""" """"' 148
7.O REFERENCES 150
X Appendix 1. Past Records of Bush stone-curlews in South Australia t62 Appendix 2. Summary of Community Questionnaire Results' n2
XI LIST OF FIGURES
CHAPTER 1
Figure 1.1. The location of Kangaroo Island, South Australia Figure 1.2. Long-term mean annual rainfall (-*) isohyets for Kangaroo Island... Figure 1.3. Location of the study sites on Kangaroo Island
CHAPTER 2
Figure 2.l. Historical and current distribution of bush stone-curlews Burhiruts grallarius in South Australia. 24 Figure2.2. Distribution of bush stone-curlews Burhinus grallarius on Kangaroo Island, determined during surveys in 1995 and 1996." .25 Figure 2.3. Frequency of response times to call playback surveys by bush stone- curlews Burhinus grallarius on Kangaroo Island. 29
CHAPTER 3
Figure 3.1. Locations of study sites for home range and movements study on bush stone-curlew s Burhinu s grall ariu,ç' ...... '...... 39 Figure 3.2. The harness design and attachment of radio-transmitters on bush stone- curlews Burhinus grallarius. 4t Figure 3.3. The timing and length of radio-tracking periods for each bush stone- curlew Burhinus gralktrius that was radio-tracked' . ".. " " " " 41 Figure 3.4a. The home range boundaries and sizes (ha) estimated by the kernel (K, (HM, dashed lines) and minimuln convex analysis techniques for six breeding bush Ilarius on Kangaroo Island. 50 Figure 3.4b. The home range boundaries and sizes (ha) estimated by the kernel (K, (HM, dashed lines) and minimum convex analysis techniques for four non-breeding s grallarius on Kangaroo Island. 51 Figure 3.5 Radio-tracking fixes and home l'ange boundaries for three bush stone- curlews Burhinus grallarius (FCl, FC2 andFC3) at Flinders chase National Park Headquarters, south-western Kangaroo Island, 1996 - 1998..,...... 55 Figure 3.6a. Frequency of 'foraging distances' for six breeding bush stone-curlews Burhinus- grallarius on south-western Kangaroo Island between 1996 and 1999. 56 Figure 3.6b Temporal patterns in 'foraging distances' for six breeding bush stone- curlews Burhinus grallarius on south-western Kangaroo Island 57 between 1996 and 1999 ...... Figure 3.7. Radio-tracking fixes and home range boundaries for three bush stone- curlews Burhinus grallarius (K84, KB7 and KB8) at 'KB Downs', south-westem Kangaroo Island, 1997 - 1999."'..."' 60 Figure 3.8. Radio-tracking f,rxes and home range boundaries for two bush stone- curlews Bctrhlru,r grallarius (KB9 and KB10) at 'KR T)owns', south- western Kangaroo Island, 1998 - 1999.."'.'... 62
xl1 Figure 3.9. Radio-tracking fixes and home range boundaries for two bush stone- curlews Burhinus grallarius (KB5 and KB11) at'KB Downs" south- western Kangaroo Island, I99l - 1998.....'.... 64 Figure 3.10a. Frequency of 'foraging distances' for four non-breeding bush stone- curlews Burhinus grallarius on south-western Kangaroo Island between 1996 and 1999...... 65 Figure 3.10b. Temporal pattems in 'foraging distances' for four nou-breeding bush stonã-cnrlèws Burhinus grallarius on south-western Kangaroo Island between 1996 and 1999...... 66 Figure 3.11. Radio-tracking fixes for five bush stone-curlews Burhinus grallarius (KBl, KB2, KB3, KB6, and KB12) at'KB Downs', south-western Kangaroo Island, 1996 - 1998...... 68
CHAPTER 4
Figure 4.1. Location of study sites for investigation of the habitats used for nesting, roosting and foraging by bush stone-curlews Burhinus 87 grall arius o n Kangaroo Island' Figure 4.2 Configuration of sampling area for each bush stone-curlew Burhinus grallarius nest site and associated random sites...... '. 89 Figure 4.3 The layout of the grid that was 'overlayed' at nest and roost areas to select random sites for samPling. 92 Figure 4.4. Relative frequency of use of three broad habitat types by bush stone- curlews Burhinus grallarius for nesting, roosting and foraging...... 95 Figure 4.5 The similarities between bush stone-curlew Burhinus grallarius nest sites and random sites on Kangaroo Island as determined by multi- dimensional scaling (a) without site labels and (b) with sites labels' ... 97 Figure 4.6 The similarities between bush stone-curlew Burhinus grallarit'ts roost sites and random sites on Kangaroo Island as determined by mutli- dimensional scaling: (a) complete data-set and (b) with the 7 outliers removed. 100
CHAPTER 5 of bush stone- Figure 5.1 . Locations of the study sites for the study of the diet curlews Burhinus grallarius. 113 Figure 5.2. Locations of micro-pitfall trapping sites at Flinders Chase Park Headquarters and'KB Downs'. ....'.'.'.... 115 116 Figure 5.3 Configuration of micro-pitfall trap sites. Figure 5.4 Percentage of bush stone-curlew Bttrhinus grallariu.s faeces containing the remains of different prey groups at Flinders Chase Park Headquafters (n: 191), 'KB Dowtts' (n : 157) and 'Brookland Park' (n:68), on westem Kangaroo lsland. t20 Figure 5.5 Percentage frequency of total numbers of prey groups recorded within individual bush stone-curlew Burhinus grallarius faeces collected for three sites on westem Kangaroo Island during 1995-1998 .tzt Figure 5.6. Seasonal variation in the percentage frequency of prey items recorded within bush stone-curlew Burhiruts grallarius faeces at (a) Flinders Chase Park Headquarters and (b) 'KB Downs'. ..'....".... .r23
xl11 Figure 5.7. Average number of captures per trap-night for each micro-pitfall trap site at Flinders Chase Park Headquarters and 'KB Downs' between June 1997 and July 1998...... 127 Figure 5.8 Bray-Curtis similarity dendogram for all micro-pitfall trap sites...'...... 728 Figure 5.9 The captures per trap-night of all prey groups for the micro-pitfall trap sites at Flinders Chase Park Headquarters and 'KB Downs'. r29 Figure 5.10. Seasonal changes in capture rates for each prey group at Flinders Chase Park headquarters and 'KB Downs'. r31
CHAPTER 6 Figure 6.1. Trends in crop production on Kangaroo Island, 1987/88 - 2000/01 r43 Figure 6.2. The current and proposed extent of agro-forestry plantations on Kangaroo Island, 2001. t44
xlv LIST OF TABLES
CHAPTER I
Table 1.1. Long-term mean maximum and minimum temperatures for four weather stations on Kangaroo Island. t2
CHAPTER 2 Table2.l. Source ofhistorical (pre-1980) and current (1980 - 1995) records of bush stone-curlews Burhinus grallarius for South Australia. 23 Table2.2 Source of current records of bush stone-curlews, Burhinus grallarius, on Kangaroo Island. 26 Table2.3 Summary of call-playback survey results for bush stone-curlews Burhinus grallarius along 13 survey transects'.. 28
CHAPTER 3
Table 3.1. The weights and age-groups of the bush stone-curlews Burhinus grallarius that were radio-tracked...... '.'. 45 Table 3.2 Radio-tracking effort and number of locations obtained for each bush stone-curlew Burhinus grallarius...... 48 Table 3.3 Estimates of home runge area for ten bush stone-curlews Burhinus grallarius using the south-westem area of Kangaroo Island. .54 Table 3.4. Fidelity to roost sites for ten bush stone-curlews Burhinus grallarius. .58
CHAPTER 4
Table 4.1. The three broad habitat categories into which all nocturnal and diurnal locations of bush stone-curlews Burhinus grallarius obtained from radio-tracking were allocated. ..88 Table 4.2. Edaphic and vegetative variables measured at each bush stone-curlew Burhinus grallarius nest site and associated random sites on Kangaroo Island. ..88 Table 4.3 Habitat variables measured for each bush stone-curlew Burhinus grallarius roost sites and associated random sites' ...'...... 91 Table 4.4. The frequency ofrecords oftypes ofground cover atbush stone-curlew Burhinus grallarius nest sites (n:27) on Kangaroo Island. ..99 Table 4.5 Features of roost sites of bush stone-curlews Burhinus grallarius on Kangaroo Island. ..99
CHAPTER 5
Table 5. 1. List of food items recorded for bush stone-curlews Burhinus grallarius frorn published literature ...... , 109 Table 5.2. Numbers of bush stone-curlew faeces collected from three locations on Kangaroo Island between 1995 and 1998 in each month of the yeat. .... , 119 Table 5.3 The results of a comparison between the diets of bush stone-curlews Burhinus grallarius at the three main study sites using the Bray-Curtis test of similarity and an analysis of similaritv (ANOSIM) ...... '. .. ' .125
XV Table 5.4 Total trap effort for each micro-pitfall trap site (trap-nights) at Flinders chase Hiadquarters and 'KB Downs' between June 1997 and July 1998...... t25
XV1 CHAPTER 1
INTRODUCTION AI{D BACKGROUI{D INFORMATION
1.0 INTRODUCTION
Bush stone-curlews Burhinus grallarius have become threatened in all States across the southern mainland of Australia. Extensive clearance of native vegetation and predation by foxes are considered the major factors in the decline of the birds (Marchant and Higgins 1993, Robinson and Traill 1996, Garnett and Crowley 2001). Bush stone-curlews are ground- dwelling birds, and roost, forage and nest on the ground, a habit that is thought to predispose a species to decline and local extinctions (Gamett 1992). Despite the decline, few ecological studies have been undertaken on this species, and little detailed information is available to determine the relative importance of the factors implicated in the decline of the birds. An understanding of the relative effects of threatening processes is critical to the development of conservation management actions to halt or reverse the decline.
In contrast to the mainland, bush stone-curlews are apparently abundant on Kangaroo Island, South Australia (Joseph 1981, Baxter 1995; Figure 1.1). Kangaroo Island's natural environment remains relatively intact as native vegetation clearance has been less severe, and has occurred much more recently, than on the adjacent mainland. Two of Australia's worst introduced pests, foxes and rabbits, are also absent from the Island, making it an ideal location to study the ecology of bush stone-curlews in an environment free of a potentially significant predator of the birds.
This study on the ecology of bush stone-curlews on Kangaroo Island commenced in 1995 and fieldwork was undertaken over a period of four years. The primary goal of the study was to increase our understanding of the ecology of these birds on Kangaroo Island, and to use this information to determine the major threats to the species and to allow conservation strategies to be developed.
1 Figure 1.1. The location of Kangaroo Island, South Australia
South Australia
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I
Kangaroo lsland
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2 1.1 BACKGROUND INFORMATION
The bush stone-curlew, Burhinus grallarius, belongs to the family Burhinidae, which consists of two genera and nine species worldwide. The genus Burhinus includes seven species that are widely distributed with four species occurring in the Old World (including three confined to Africa), two species in Central and South America, and the one species in Australia (Cramp 1983). The other genus, Esacus, includes only two species and is more restricted in distribution, occurring from the Indian subcontinent to New Guinea and northern Australia (Cramp 1983). The beach stone-curlew, Esacus magnirostrls, is the only other species from Burhinidae to occur in Australia.
Information on the distribution,habitat, social organisation, diet and breeding biology of bush stone-curlews is reasonably well known from anecdotal observations made by amateur and professional ornithologists (see Marchant and Higgins 1993), although few detailed studies have been undertaken (e.g. Johnson and Baker-Gabb 1994). In addition, many aspects of bush stone-curlew ecology, including social organisation, social behaviour and vocalisations have not been specifically studied in any detail. Below is a summary of what is known about these birds.
1.1.1 Description
Bush stone-curlews arc large terrestrial birds with cryptic plumage that makes them difficult to observe within their roost areas during the day. They have a slender body, and long legs that reflect their ground-dwelling habits. Another characteristic, which is common amongst all species within the family, is an enlarged tibio-tarsal joint, which gave rise to their previous common name of thick-knees. Bush stone-curlews have a hunched appearance and large pale
eyes set in a big rounded head. The large eyes provide stone-curlews with excellent day and night-time vision (Martin andKatzir 1994). The birds range in weight from 625-1267 grams (Marchant and Higgins 1993), although almost no data on weights from temperate Australia exist. The birds are approximately 350mm tall.
The sexes of the species are alike although females are slightly smaller. In captive birds at Healesville Sanctuary females can be reliably sexed based on white areas of plumage, especially on the head, which look consistently more off-white than in males (Marchant and Higgins 1993). Whether this character is effective for sexing birds in wild populations is not known.
Ja Some variation in plumage and size occurs across the range of the species, although this is considered mostly clinal, and no subspecies are recognised. A rufous morph occurs in northern Australia and intergrades with a grey morph on the east and west coasts. Birds from the north of Australia are slightly smaller than birds in the south (Marchant and Higgins ree3).
Bush stone-curlews are wary and difficult to observe, and typically walk away slowly or fly when disturbed. Occasionally they squat on the ground and rely on their cryptic plumage to hide them. At night bush stone-curlews spend much of their time in open areas while during the day they are generally inactive and stand quietly (Marchant and Higgins 1993).
1.1.2 Distribution
Marchant and Higgins (1993) provide a detailed account of the distribution of the bush stone- curlew. They are widespread in the north and northeast of Australia and absent or scattered inland. Only sporadic records occur in the south and east of Australi a aftet a contraction in range. In South Australia, there have been few records in recent years and most are from Kangaroo Island. A few scattered records from southem Eyre Peninsula, the Lake Eyre drainage basin, the Murray Mallee and the South East have occurred. However, the birds were formerly widespread and common in the north, northeast, Murray Mallee, Adelaide plains and South East (White 1919, McGilp 1939, Boehm 1960, Mack 1970, Attiwlll 1972, Badman lg79). The contraction of range in South Australia has not been fully documented and whilst it is generally accepted that Kangaroo Island is now a stronghold (Joseph 1981, Baxter 1995) detailed studies of the distribution of this bird on the island have not been undertaken. These birds are now classified as endangered in South Australia, following a major range contraction. A similar situation exists in Victoria (Johnson and Baker-Gabb l9g4) and'Western Australia (Saunders and Ingram 1995). Generally populations of the birds appear to persist in areas where foxes are absent, such as temporary islands in the Murray River and offshore islands, including Kangaroo Island.
1.1.3 Habitat
Prior to European settlement bush stone-curlews are thought to have predominantly occurred in lowland grassy woodland and open forest in southem Australia, although much of this has now been cleared for agriculture (Johnson and Baker-Gabb 1994). Today bush stone-curlews typically occupy lightly timbered areas of woodland or forest, including farmland with remnant patches of native vegetation. They appear to prefer areas where the ground cover
4 consists of short sparse grass and few or no shrubs. In addition, the ground may be covered with leaf litter and other fallen debris such as dead tree branches (Marchant and Higgins 1993). In inland Australia bush stone-curlews are geîerally found around ranges, lakes and watercourses with permanent water (Marchant and Higgins 1993)'
The few detailed studies of habitat have been in highly modified environments where native vegetation exists in small isolated remnants (e.g. Johnson and Baker-Gabb 1994). As such, the results of these studies reflect the habitat that is available now, and not necessarily the preferred habitat of these birds.
The birds roost on the ground among leaf-litter, often amongst clumps of shrubs or trees, including small isolated remnants and roadside vegetation (Marchant and Higgins 1993). In northern Victoria the birds were found to roost in areas where percentage cover of fallen tree debris was higher, there was more bare ground, lower grass and less disturbance from farming than in surrounding areas (Johnson and Baker-Gabb 1994)'
Bush stone-curlews are known to nest in open woodland areas with short and sparse grass' Eggs are laid directly on the ground and no nest of any description is constructed. Within open woodland areas nests are often placed near fallen timber (Marchant and Higgins 1993), although Johnson and Baker-Gabb (1994) found nests to be on average l2.J mettes from the
nearest tree, which is also consistent with the selection of open woodland areas. Nests are also occasionally placed in short grass or in fallow or recently ploughed paddocks (Johnson
and Baker-Gabb 1994).
Bush stone-curlews forage on open ground, sometimes under trees, among grass, pasture or crops, irrigation paddocks, and in summer, around watercourses, dams and swamps (Marchant
and Higgins 1993). Due to the difficulties of observing these birds at night no detailed studies of habitat used for foraging or foraging behaviour have been undertaken.
1.1,4 SocialOrganisation
Bush stone-curlews are considered sedentary. They appear to be territorial during the breeding season, although there are records of local movements during the non-breeding season. Johnson and Baker-Gabb (1994) found that the birds generally inhabited the same and area throughout the year. Breeding birds appear to forage near the nest, although off-duty
5 non-breeding birds may band together and travel further to forage (Schodde and Mason 1980). There is no evidence of large-scale movements.
Bush stone-curlews are typically monogamous and appeff to retain this bond all year and for long periods. They are usually found singly, in pairs, or as families with 1-3 young, although groups of up to 60 birds have been recorded (Marchant and Higgins 1993). If one partner dies then another mate is likely to be found. One tame bird apparently 'took fancy' to a motorcycle, and slept near its wheel. However, the attachment ended when the bird paired with a conspecific. The fate of the heartbroken motorcycle was not described (Marchant and Higgins t9g3). Both sexes are involved with incubation, defence and rearing of the young.
During the non-breeding season some bush stone-curlews remain as resident pairs (Johnson and Baker-Gabb lg94) while others form small flocks, typically of 5-10 individuals (in southern Australia), which may account for apparently erratic changes in numbers (Schodde and Mason l9S0). These flocks are thought to move around locally. As the breeding season approaches the flocks separate as birds re-establish territories. Pairs often nest near traditional roost and nest areas. Johnson and Baker-Gabb (L994) found that in the past, in northem Victoria, four breeding pairs would occupy aî atea of approximately 290 hectares, although today only one pair or fewer occupy the same area (Marchant and Higgins 1993)'
During the breeding season territory sizes have been estimated at between 10 and 25 hectares 'Wilson (Schodde and Mason 1980; Johnson and Baker-Gabb 1994; 1989) and birds remain within this area for up to eight weeks (Johnson and Baker-Gabb 1994). At other times the birds move within a loosely defined home Íange, the size of which is probably determined by availability and distance between suitable roosting areas. In Victoria, Johnson and Baker- Gabb (1994) estimated that the diurnal home-range was up to 250 hectares per bird peÍ year' but the nocfurnal home range was much larger. In suburban Brisbane, Anderson (1991) noted that the birds moved well beyond their day-time roost when not breeding, and may have foraged over 95 hectares, but this was probably reduced to 41 hectares when the birds had
dependent young.
Other observations indicate that one pair of bush stone-curlews only moved between five favoured day shelters within a 12hectare atea, and another pak roosted within one day shelter that was less than one hectare all year round (Johnson and Baker-Gabb 1994). Aûother family was usually located within one kilometre of its nest, and rarely ranged beyond two and
6 a half kilometres av/ay. Pairs appear to roost in the same site every day for weeks, or even months if undisturbed (Johnson and Baker-Gabb 1994). Some birds are likely to use a suitable site all year round, only leaving if food becomes scarce, or if the habitat is altered (Johnson and Baker-Gabb 1994),
Whilst a reasonable amount of data are available on social organisation (see Bright 1935, Bedggood 1977, Anderson 1991 and Johnson and Baker-Gabb t994) most has come from a couple of studies. Wide ranges of estimates of home range size arc suggested, and this aspect of the birds' ecology requires further study.
1.1.5 Diet
The diet of bush stone-curlews is varied but consists mainly of insects, molluscs, centipedes, crustaceans, spiders, frogs and lizards (Marchant and Higgins 1993) and is thought to vary little throughout the year (Johnson and Baker-Gabb 1994). In Victoria a study of faeces found insect exoskeletons in 55olo, soil and gravel inllo/o, vegetation in4o/o, feathers, hair or bones in 5Yo, and uric acid in 20% (Johnson and Baker-Gabb 1994). Marchant and Higgins (1993) list a wide range of invertebrates in crops and stomachs of bush stone-curlews, and
should be referred to for more detail.
1.1.6 Yocalisations
The presence of bush stone-curlews is typically only alluded to by their eerie wailing calls at night. Many rural landholders are aware that these birds occur on their properties although they rarely see them. No detailed studies of voice have been undertaken. The birds call most nights and typically begin around dusk when a chorus erupts between neighbouring pairs (pers. obs.). The amount of calling through the night varies, and the birds are thought to be a lot more vocal on moonlit nights (Marchant and Higgins 1993). The call is typically described as a 'weer-loo' and usually four or f,rve of these wails are made in succession increasing in speed to a finale of much screeching that sounds like more than one bird is involved. Both sexes make the calls, which are apparently used to make contact and define territories. The birds also have a series of calls associated with taking flight (if disturbed),
alarm, and softer contact calls used between pairs (Marchant and Higgins 1993).
7 1.1.7 Breeding biology
The breeding biology of bush stone-curlews is reasonably well known from studies undertaken by Johnson and Baker-Gabb (1994), Anderson (1991) and Andrews (1997). Breeding generally occurs during spring throughout the range of the birds, and in South Australia eggs have been reported in mid-July and early and late September (Marchant and Higgins lg93). Pairs typically re-nest in the same location and, in Victoria, Johnson and Baker-Gabb (1994) found thatT5o/o of known breeding sites had been used regularly for over ten years. Usually the birds lay two eggs although clutches of one to three, and rarely four, have been recorded. Both sexes incubate the eggs, which begins when the clutch is complete and takes approximately 25 days (Marchant and Higgins 1993)' young birds are able to fly when approximately eight weeks old although the period of parental cafe may last up to 20 weeks. Johnson and Baker-Gabb (1994) found that at ten sites the young remained in the nesting area with the parents for three to nine months. This may depend on whether or not the birds have multiple clutches (Marchant and Higgins 1993)'
Breeding success varies, and requires further study, as it is critical to the long-term survival of this species in areas where they are in decline. Johnson and Baker-Gabb (1994) found that from a total of 52 eggs laid, 30 survived four weeks or less, and Il survived beyond four weeks, although from2} two-egg clutches only two pairs raised both chicks to independence. Anderson (1991) determined that from six clutches observed in parks in Brisbane, f,tve chicks survived to independence. Little is known about the long-term survival ofjuveniles.
1.1.8 The decline of woodland birds on the mainland
Bush stone-curlews have been associated with a suite of bird species that are dependent on temperate woodlands across southern Australia (see Robinson and Traill 1996). Temperate woodlands have become the most threatened ecosystem in Australia, and consequently this habitat type contains a very high number of threatened taxa, including many birds. Ovet 85Yo of the woodland that once covered a large area of eastern and south-westem Australia has been cleared, and replaced by wheat and sheep production (Robinson and Traill 1996)' 'Woodlands growing on relatively fertile soils were cleared disproportionately and much of the
remaining habitat occurs on rocky slopes and hills. This situation exacerbates the problem for woodland dependent fauna, as the remaining habitat is of relatively poor quality, and is not likely to provide the complete suite of resources required by the fauna. The impact on woodland birds is clear, and not surprisingly one of the highest concentrations of threatened birds in Australia occur within this habitat (Robinson and Traill 1996). However, of greater
8 concem is the decline of many apparently "common" species, and the implications of the 'extinction debt' theory. This theory suggests that because the clearance of woodland habitats has occurred relatively recently, and habitat fragmentation and degradation continues today, it is likely that many species will not be able to persist within this modified environment. Whilst these species may be present today, and relatively common, the long-term impact of clearance is still to be seen. The general decline of woodland birds is particularly evident in 'Western the Australian wheatbelt where nearly 50%o of all birds, and 88% of resident passerines have declined in range or abundance since European settlement (Saunders and Ingram 1995). Research and active management is urgently required to try and reverse this situatron.
I.2 AIMS AND OBJECTIVES OF THE STUDY
The broad objective of this study was to improve our understanding of the ecology of bush stone-curlews on Kangaroo Island with a view to identifying threats to the birds and to making management recommendations aimed at ameliorating these threats, both on Kangaroo Island and on the mainland of South Australia. The specific research objectives of the project were:
l. To document and discuss the historical distribution, and decline, of bush stone-curlews in South Australia. Z. To determine the current distribution and status of bush stone-curlews on Kangaroo Island. 3. To determine the home range sizes of bush stone-curlews at two sites on Kangaroo Island. 4. To determine the characteristics of foraging habitat, day roost areas and nest sites, and discuss the availability of these habitats on Kangaroo Island. 5. To determine the diet of the bush stone-curlews on Kangaroo Island by examining faeces, and to make comparisons with invertebrates captured in pitfall traps located within foraging habitat.
1.3 THE STUDY SITES 1.3.1 Kangaroo Island - A General Overview
Kangaroo Island is situatecl just off the coast of mainland South Australia (Figure 1.1), south (excluding of the Fleurieu and yorke peninsulas, and is the second largest island in Australia
9 Tasmania), measuring approximately l60km by 40km. Although connected to the mainland during the last ice age, current estimates indicate that the island was isolated from the mainland around 8,900 years BP (Wells et a\.2000). The narrowest strait, called Backstairs
Passage, is now approximately 14km across'
The first attempt to establish a settlement on the island was in 1836, however, this attempt failed. Following this the island developed slowly as an isolated agricultural community.
'War Most agricultural development occurred after the Second World through the soldier (Ball settler scheme. Today approximately 50o/o of the island has been cleared for agriculture and Camrthers 1998). Approximately 4,000 people live on the island and tourism and primary production are the major sources of income'
Kangaroo Island is very bio-diverse and supports vertebrate species that are threatened or extinct on the mainland. One of the most signifîcant factors contributing to this is that foxes and rabbits \ryere never introduced to the island. As a result, species that are absent or scarce on the mainland have continued to thrive on the island, including bush stone-curlews'
Landforms Kangaroo Island consists primarily of a large east-west central plateau, which terminates in high cliffs to the north, and gradually slopes towards the southem coast. The plateau developed during a Pleistocene-Recent uplift of an old plain and is capped with an ironstone the crust known as laterite (Daily et at. 1989). A narrow strip of relatively flat land forms water-shed, separating south and north flowing rivers. This ridge reaches a maximum height of approxim ately 275min Flinders Chase National Park. To the south the land slopes towards a coastal rim of high dunes and consolidated dune limestone, known as calcarenite. cliffs formed by these consolidated dunes dominate much of the south and south-western coast. The intersection of the plateau and the southern rim of dunes forms an area of swamps and lowlands, which have poor drainage as most creeks are deflected by the barriers of sand and calcarenite (Daily et al.1989).
Climate Detailed information on the climate of Kangaroo Island can be found in Burrows (1979) and Robinson and Armstrong (1999).
l0 to Kangaroo Island has a more equable climate than most areas of the adjacent mainland due its small size and low elevation, and the moderating influence of the sea. The climate is cool and temperate with maximum rainfall in winter.
Long-term meteorological measurements are avatlable for several locations, including the Cape Borda Lightstation, which commenced operation in 1885, the Cape du Couedic lightstation, Kingscote, and the Parndana Agricultural Research Centre. The hottest months and are January and February and the coolest are July and August. The mean daily maximum minimum for January and July are shown in Table 1.1. Average rainfall ranges from under (Figure 1.2). 500mm around Kingscote to over 800mm on the western end of Kangaroo Island This reflects the topography of the island, and the influence of the main east-west plateau and ridge. The rainfall is highly seasonal with up to 50o/o of average totals falling in winter and only l0% in summer. Drought years were recorded on 11 occasions between 1869 and 1967 (Department of Environment and Planning 1986).
to The prevailing winds between December and March are south-easterly, and in April a shift north-westerly occurs for the winter, with variable winds between September and November' The positions of the mid-latitude anticyclones (high pressure systems) are the main determinants of these conditions.
1.3.2 Flinders Chase National Park Headquarters (FCHQ), Detailed study of the birds took place at Flinders Chase National Park Headquarters these sites are and a nearby agricultural property called 'KB Downs' (see below)' Both of located on south-westem Kangaroo Island (Figure 1.3)'
The FCHe is located near the lower reaches of the Rocky River in an atea that was initially south- cleared for agriculture in the 1870s. The site is located near the intersection of the lowlands sloping plateau and the southern dunes, as described above, and includes areas of have and swamps, and consolidated dune ridges consisting of calcarenite. Bush stone-curlews been recorded in this area for many years (e.g. Cleland 1942) and probably established Today themselves in the area soon after the initial clearance took place in the early 1870's. offices and the area is the administrative centre of Flinders Chase National Park and includes
residences as well as camping facilities'
1l Table 1.1. Long-term mean maximum and minimum temperatures for four weather stations on Kangaroo Island.
All temperatures are in degrees Celsius. Observations at Cape Borda commenced in 1885 and continuè today. Observãtions at Cape du Couedic commenced in the early 1900's and the stopped ín tglZ when the light becáme automated. The periods of observations for paÀìana Agricultural Reseaich Centre and Kingscote are not known. Sourced from Department of Environment and Planning (1986)'
Stations Mean Daily Maximum (uC) Mean Daily Minimum ('c) January July January JulY 9.0 Cape Borda 22.4 t3.6 t3.6 Cape du Couedic 2r.5 14.4 14.2 9.4 6.8 Parndana Agricultural 24.9 13.6 12.4 Research Centre Kingscote 23.5 14.4 14.6 8.3
Figure 1.2. Long-term mean annual rainfall (mm) isohyets for Kangaroo Island' (1999) Note that the 550mm isohyet is not shown. source: Robinson and Armstrong
F ainf¡ll leo hYets # NPW SA Resetres N åtive Ve get¿tion
l2 Figure 1.3. Location of the study sites on Kangaroo Island
NPWSA R eserves Native Vegetalion 0 10 ?fl Kilometres A H
13 The vegetation at FCHQ is a mix of communities associated with the river, and adjacent swamps, as well as the consolidated dune ridges. Much of this vegetation has been modif,red by the long-term use of the site for pastoral activities from the time of settlement (ca. 1870s). The main vegetation community is an open woodland/forest with a mixture of eucalypts including sugar gum Eucalyptus cladocalyx, pink gum E. fasciculosa and swamp gum E. ovata. The understorey of this community is quite sparse and includes species such as mintbush Prostranthera spinosa, sweet bursaria Bursaria spinosa, and kangaroo thorn Acacia paradoxa, with a ground cover predominantly consisting of morning flag Orthrosanthus multiflorus. Adjacent to the clumps of open forest are dense areas of shrubs associated with poorly drained depressions. These areas are dominated by tea-trees Leptospermum species, and slender honey-myrtle Melaleuca gibbosa, with clumps of swamp wattle A. retinodes var. unciþlia. Mixed in with these communities are open areas of heathy shrublands and these are characterised by species such as cup gum E. cosmophylla, Banl The consolidated dune ridges and associated areas are covered tall mallee with a sparse "vith understorey. The common mallee species are coastal white mallee E. diversiþlia' and Port Lincoln mallee E. lansdowneana. The most common understorey species is dryland tea-tree M. Ianceolata, and morning flag provides a dense ground cover in places. Velvet bush Lasiopetalum schulzenii, and Coruea reflexa are also common. The pastoral activities in this area have partly modified these vegetation communities, particularly the understorey. Other areas were regularly ploughed in the past and the vegetation is regrowth. 1.3.3 KB Downs KB Downs is a large agricultural property located approximately 10km east of Rocky River on the South Coast Road (Figure 1.3). It is bordered by Flinders Chase National Park to the west, the South Coast Road to the nofth, Hanson Bay Road to the east, and the Southern Ocean. KB Downs is also located near the intersection of the south-sloping plateau and the t4 southem dunes, and the landscape is gently undulating with small limestone ridges and stony swales covering much of the property. Several small swamps and associated low-lying areas can be found on the westem parts of the property, and small areas of laterite associated with the Island's plateau are also present. Much of the southern half of the property contains the original vegetation and the remainder consists of cleared pasture, with smaller patches of remnant vegetation. Clearance on this property took place much more recently than FCHQ, in the 1960s and 1970s. During the course of the study KB Downs was de-stocked as people interested in maintaining and enhancing its conservation values purchased the property. Despite the de-stocking the pasture is kept shortby an abundance of tammar wallabies Macropus eugenii that shelter in the surrounding areas of vegetation during the day. The areas of improved pasture have not had any super-phosphates added in recent years, although a clover is still present, and dandelions grow prolifically on these paddocks. The original vegetation remaining on the southern part of the property provides an important link between Flinders Chase National Park and Kelly Hill Conservation Park and beyond. However, this area is not used by the bush stone-curlews and only the vegetation communities fringing the cleared land will be described here. Most of the remnants remaining within the cleared areas occur on stony calcarenite ridges and comprise low mallee trees dominated by coastal white mallee and Kingscote malle e E. rugosa. Few shrubs occur on these ridges probably due to the poor substrate. Mallee and mallee-health surround much of the cleared land and consist primarily of the two species mentioned above, along with cup gums. A diverse and variable shrub layer occurs within these communities, with common species including dryland tea-tree, striped hakea H. vittata, beaked hakea H. rostrata, Banl to those at FCHQ. 15 I.4 STRUCTURE OF THE THESIS This thesis is compiled as a series of chapters. As such each of Chapters 2-5 are self contained with an introduction, full description of methods, results, and a discussion. Because these Chapters stand-alone there is some repetition between each, and this is intentional as it allows each chapter to be read in isolation of others. The major findings of the study and management recommendations for the species are presented in the final chapter (Chapter 6). Chapter 2 reports on the decline of bush stone-curlews across South Australia and outlines the results of a detailed investigation into the current distribution of the birds on Kangaroo Island. The importance of the population on the island is discussed. Chapter 3 details the results of an intensive radio-tracking study that was undertaken to determine home range sizes of the birds and to investigate spatial and temporal use of these home ranges. The results obtained from tracking 15 birds for periods of three to 18 months are outlined. Chapter 4 details information obtained on the habitat preferences of the bush stone-curlews, and in particular the characteristics of sites chosen for nesting, roosting and foraging. The availability of the preferred habitat is discussed along with likely future impacts. Chapter 5 reports on a study of the diet of the birds. Diet was determined by examining faeces, and is compared to specimens of invertebrates collected in pitfall traps located within the foraging habitat. Finally, as indicated, Chapter 6 draws on all the information from the previous chapters and discusses potential impacts on the population and strategies for ameliorating these impacts. Management strategies and recommendations are made, with the aim of ensuring that bush stone-curlews remain a common feature of Kangaroo Island's wildlife' t6 CHAPTER 2: THE HISTORICAL AND CURRENT DISTRIBUTION OF BUSH STOI{E-CURLE\ry S, B URHI]YUS GRALLARIUS' IN SOUTH AUSTRALIA AND OI{ KANGAROO ISLAND. 2.0 INTRODUCTION The bush stone-curlew, Burhinus grallarius, occurs throughout southern and northern Australia. Despite being widespread in northem and north-eastern Australia the birds have suffered a major range contraction in southern and eastem Australia (Marchant and Higgins 1993). As a result, numbers of bush stone-curlews appear to have declined considerably in the settled areas of southern Australia and probably continue to do so (Johnson and Baker- Gabb 1994). In South Australia these birds are classified as endangered (Schedule 7 NPV/S Act 1972), having suffered a major reduction in range and abundance. In Victoria the range and abundance of these birds has also decreased and widespread regional extinctions have occurred in the south of the State. As a result these birds are considered vulnerable in Victoria (Johnson and Baker-Gabb lg94). Similarly, in the south-west of westem Australia, bush stone-curlews have undergone a major range contraction and are now considered rare (Saunders and Ingram 1995). Although still common in the north of Australia, Garnett and Crowley (2002) listed these birds as near threatened in recognition of the marked population decline that has occurred in the south (Garnett and Crowley 2000). In South Australia only a few scattered records continue to come from the mainland, in particular near Renmark in the Riverland and near Bordertown in the South-East of the State (South Australian Omithological Association, unpublished records). Records also come from the off-shore islands atthehead of Spencer Gulf, although the majority of recent records have come from Kangaroo Island (South Australian Ornithological Association, unpublished records). Despite the increased popularity of 4WD touring through the northem parts of the north- State, very few recent records come from these areas. Senior A¡angu people from the west of the state are familiar with this bird (known as 'wiiloo' in reference to its calls) and have also noted its decline, and now consider it very rate (L. Rive pers' comm')' Two main factors have been implicated in the deolirre uf this species in southcrn and eastern Australia - the modification or loss of habitat and predation by foxes (Marchant and Higgins t7 1996). 1993, Johnson and Baker-Gabb lgg4, Saunders and Ingram 1995, Robinson and Traill processes As with many endangered species direct evidence of the effects of these threatening is difficult to find. However, much anecdotal and circumstantial evidence exists, particularly with regard to impact of foxes. Many early ornithologists believed that foxes were the primary cause of local extinctions (eg for South Australia see Cleland 1924, White 1925, Newell l9Lj, pearse 1929 and Boehm 1934). Although the establishment of foxes did coincide with the decline or local extinction of the bush stone-curlew in some regions, small populations do persist in a few areas where foxes are common (Marchant and Higgins 1993)' in The birds also seem to have disappeared from much of the arid interior, where foxes occur low numbers Kangaroo Island is of particular interest in South Australia because of the high numbers of on recent records. Joseph (1981) considered that the birds were 'nothing short of common' the island, and Baxter (1995) also records them as widespread. Presumably an important has the most reason for this is the lack of foxes, and as a result Kangaroo Island probably particularly the secure and viable population of bush stone-curlews in southern Australia, if about bird continues to decline on the mainland (Joseph 1981). Despite this, little is known this important population. This study sought to answer the following questions: l. What was the historical distribution of bush stone-curlews in South Australia? Z. What is the present distribution of bush stone-curlews in South Australia? 3. What is the current distribution of bush stone-curlews on Kangaroo Island? 2.I METTIODS 2.1.1 Historical and current distribution across South Australia in A thorough literature search was undertaken to find past records of bush stone-curlews in South South Australia. This provided a summary of historical information for the species Australia along with information on its current distribution. This information was coupled with the Birds Australia (formerly Royal Australasian Australia Atlas Ornithologists Union) Atlas database to develop distribution maps. The Birds records obtained database was not referenced and therefore it was necessary to crosscheck from the literature and museum to ensure that records were not duplicated' 18 Records were also obtained from the South Australian Ornithological Association, including many since the Birds Australia database was compiled. Past and present Kangaroo Island residents with a particular interest in birds were also contacted to obtain their records of bush stone-curlews. All records were allocated to four time intervals (pre 1940,1940 - 1959; 1960 - t979; and 1980 - 1995) to investigate changes in distribution in historical times (pre-1980) and to determine the current distribution of the birds ( based on records from 1980 - 1995). 2.1.2 The Kangaroo Island surveY The cryptic nature of this bird makes it difficult to detect and its presence usually goes unnoticed, except for its eerie wailing calls that are commonly heard at night. Therefore to determine the distribution of these birds on Kangaroo Island census techniques that relied on these vocalisations were developed. Bush stone-curlews always responded to taped recordings of their calls played at Flinders Chase National Park Headquarters (FCHQ). This method was trialed approximately 15 times (pers. obs.). At least two breeding pairs were known to occur at this site and their response to the call playback was usually immediate, regardless of the time of night. Therefore a census technique based on call-playback was developed to fast track the detection of bush stone-curle\rys across the island. The temporal patterns of vocalisation of bush stone-curlews have never been quantified using rigorous sampling methods and are therefore not well understood. However, it was decided to coordinate the surveys to occur in the breeding season, between July and Jamary, when it was expected that the birds would be more vocal as they proclaimed their breeding territories' Two strategies were therefore used for undertaking the distribution survey. Call-playback surveys were undertaken along road transects across the island, and questionnaires and survey forms were distributed throughout the rural community, and primarily relied on landholders ability to recognise the calls of the birds. Call-playback surveys Call playback has become a standard method for censusing owls (e.g. Hill and Lill 1998, Redpath lgg4, Kavanagh and Peake 1993, and Hardy and Morrison 2000). It has also been used for cryptic species such as rails (Legare et al. 1999) and other waterbirds (Gibbs and Melvin I9g3). The effects of seasonal, temporal, lunar and biological factors, as well as weather conditions, on response rates of birds to call-playback have generally not been quantified (Hardy and Morrison 2000). However, the effects of wind on the call-playback t9 technique are widely recognised (see Hill and Lill 1998, and Hardy and Morrison 2000), and following a review of papers on the census of owls, Smith (1987) concluded that wind had the most significant impact on the amount of calling heard. Although not quantif,red the results of preliminary surveys at FCHQ demonstrated that the birds responded in a wide range of weather conditions, and lunar phases. Based on this information suryeys were only undertaken on calm nights, with less regard to the other variables. Call-playback surveys for bush stone-curlews were undertaken along transects established across Kangaroo Island. Transects followed roads from the north to the south, and surveys were undertaken at two to four kilometre intervals along these transects. For ease of locating survey sites (for future reference) most sites were located either at road intersections, or at midpoints between intersections. For mapping purposes Australian Map Grid references for each site were determined using a GPS or odometer readings from the car and all survey points were plotted on 1:50,000 topographical maps. Hal Crouch supplied a tape of the bird's calls. Calls were played for half a minute followed by four and a half minutes of 'listening' time. These f,rve-minute cycles were repeated up to three times, providing a maximum of 15 minutes survey time at any one site' The same 30 seconds of taped calls was played throughout the surveys. Tapes were played in a Superscope C-1034 cassette recorder, connected to two Arista SPH4 15 watt horn speakers (supplied by Hal Crouch), which were mounted on a wooden box that was placed on the car roof. The 'When speakers were generally rotated outwards to face away from the road. birds responded, the time from the start of the survey (when the tape was first played) was noted and then approximately one minute was spent listening for responses from other birds. The number of birds, or groups of birds, responding and their direction from the car was also noted' If the birds were calling on arrival at a site the above details were recorded without undertaki¡rg the call-playback survey. It is estimated that calls could be heard fuom 2-3 kilometres on still nights, although this was affected by the local topography. The call-playback surveys were only undertaken on calm nights that provided optimal 'listening' conditions. Three transects were re-surveyed approximately one year after the initial survey to compare spatial patterns of response between years. 20 Community based surveys As indicated above the local community was enlisted to assist with surveys to complement the distribution data obtained from the call-playback transects and to increase the coverage of the survey. Landcare Groups, schools and staff of the National Parks and Wildlife Service were invited to take part in surveys on specified nights and/or by completing a questionnaire. Vocalisations of the birds provided the basis for determining presence or absence. The community volunteers were encouraged to listen for up to two hours on specif,ted nights, and to indicate if any calls were heard within l5-minute blocks. Data sheets were provided with survey dates and times and participants were asked to indicate the l5-minute blocks of time during which they listened and whether or not they heard the birds in each of those 15- minute blocks To determine the best time to undertake surveys the times when bush stone-curlews called were recorded for 22 fptart)nights between March and July 1995 at FCHQ. Temporal pattems of vocalisation varied considerably between nights, however, on every evening the birds called at least once at dusk, and often considerable calling took place at this time (pers. obs.). Surveys were therefore organised to occur immediately after dusk, which was also considered to be a relatively convenient time for community members. To encourage as much community involvement as possible, five survey periods of three days I - each were chosen. These dates were August 27 -29, September 7 -9 and 20-23, and October 3 and 8-10 in 1995. I anticipated that participants would find at least one night when they could undertake the survey. Start times for the surveys were determined in advance by obtaining sunset times for Adelaide for each of the survey dates and adding 45 minutes to reflect the approximate time after sunset that the birds at FCHQ first called. Allowance for variations in the level of darkness and different weather conditions were made. Data sheets were distributed to Landcare groups through their secretaries, to schools via nominated teachers, and directly to National Parks and Wildlife staff through site managers at the six main offices. Importantly the data sheets had provision for personal and properly details to be included so that Australian Map Grid references could be determined for each record. Instructions and hints were included on each data sheet, in particular the fact that calm nights were better for hearing the birds. Simplified data sheets were distributed to school children along with audiotapes of calls to ensure that they knew whal" Lhc birds sounded like. 2L In addition to the specific surveys, a questionnaire was developed to collect information on: whether or not landholders had the birds on their properties; how recently they had heard the birds; whether or not they saw the birds and where; and if observations of breeding had been made (see Appendix 2). The questionnaires were distributed directly to National Parks and Wildlife staff and they were included in the local Landcare Newsletter, which was distributed to every landholder on Kangaroo Island (c. 500) outside of the town areas' prior to the surveys articles were placed in Kangaroo Island's local nev/spaper, and in the Landcare Newsletter to try to encourage involvement. Follow-up articles were also written for these publications to encourage the retum of the data sheets and questionnaires. Also, an invitation to speak about this project at a Wildlife Disease Association conference in October 1995 provided an opportunity to involve this group of people in a 'listening' survey at dusk' A small number of records were obtained from this group. 2.1.3 I)ata storage and analYsis this A database was established in Microsoft Access for storing all records. Information from and database was transferred to the Geographic Information System (GIS) programs Arc-info Arcview. Analysis and presentation of data were undertaken with both of these programs. 2.2 RESULTS 2.2.1 Historical and recent records for South Australia A total of 4I4 records were collected (see Appendix 1), the majority of which were already in the Birds Australia database (Table 2.1). The historical records of bush stone-curlews in over the South Australia (Figure 2.1) clearly show the decline in distribution that has occurred last century. A small number of recent records come from areas where small populations are known to persist, such as near Renmark, near Bordertown, and on several offshore islands. Figure 2.1 and Table 2.2 conflrmed that the majority of recent records have come from Kangaroo Island. 2.2.2 The Kangaroo Island surveY A total of 235 recent records were obtained during the current survey (Figure 2'2), of which landholders. 109 were obtained from the call-playback surveys and126 were obtained from Table 2.2 shows a breakdown of the sources for recent records of bush stone-curlews on Kangaroo Island. 22 j -l i: -.r '.1 I I I i .\ (pre-1980) and current (1930 1995) records of bush { Table 2.1. Source of historical - I -l stone-curlews Burhinus grøllørils for South Australia. i t The source of all historical records is given. The table shows the number of records not listed within the RAOU Atlas data-base for each source. Numbers in brackets indicate the total number of records for each source, including those duplicated in the RAOU Atlas data-base. SAOA : South Australian Ornithological Association . RAOU : Royal Australasian Ornithological Association. Source No. SA Museum 14(2r) Journals 48(80) SAOA 25(28) Personal Communications 31 RAOU Atlas 296 TOTAL 414 23 Figure 2.1. Historical and current distribution of bush stone-curlews Burhinus grallarius in South Australia. points indicate the locations where bush stone-curlews were detected in each of the four time periods: pre 1940; 1940-1959; 1960-t979 and 1980-1995. I t a a ¡O a o a a a a a o a a a a a o oa r¡ t Pre 1940 1940 - 1959 - 1960 - 1979 1980 1995 24 Figure 2.2. Distribution of bush stone-curlews Bu¡hinus grallørius on Kangaroo Island, determined during surveys in 1995 and 1996. Catl-playback transects are shown as bold lines, with locations where the birds were present shown in red and locations where they were absent shown in yellow. The locations of records obtained from the community via 'listening' surveys and questionnaires are shown as blue triangles. Areas of NP\{SA reserves and remnant vegetation are also shown. Call-playback Survey Resu lts Â/ survey Transects o Bush Stone-curlews Present o Bush Stone-curlews Absent a Community Records I NPWSA Reserves ii¡i;,i Remnant native vegetation 20 Kilometres A 25 Tab\e 2.2, Source of current records of bush stone-curlews, Burhinus grallaríus, on Kangaroo Island. Source of all of the current records of bush stone-curlews for Kangaroo Island are shown' a Landcare Newsletter euestionnaires and survey forms were distributed to all landholders in and via Landcare Groups. All NPWSA staff were contacted via their work site. School children (Kingscote were contacted througñ th.ir newsletter (Pamdana Area School) or during lessons Area School). Memters of the Wildlife Disease Association conducted 'listening' surveys during a conference. Personal communications were unpublished records obtained from Kangãroo Island residents. Transect records were obtained from call-playback surveys' Source No. 7o Return Transects 109 nla Landholders - questionnaire 38 8 Landholders - survey forms 8 7 NPWSA Staff - questionnaires and/or JJ 63 surveys Schools 5 >5 V/ildlife Disease Association 8 nla Personal Communications 34 nla TOTAL 235 26 Call-playback surveys The 109 records obtained from the call-playback surveys were obtained along 13 transects that were established across the length of the island (Figtre 2.2). Nine of the 13 transects were surveyed between September and Decemb er 1995, three were surveyed in July 1996 and one was surveyed over several nights between these dates. Eight transects were suryeyed during single nights, three were surveyed over two nights, and two were surveyed over three or more nights. Surveys were only undertaken over two or more nights if weather conditions deteriorated, making it impossible to complete the survey. All surveys were undertaken between dusk and 2.00am A summary of the transect survey results can be seen in Table 2.3. Of the 147 surveyed sites, bush stone-curlews were recorded at I09 (14%), and were absent at38 (26%). However, of the 3g sites where they were absent 3l (82%) of these occurred in large areas of native vegetation: 26 (6g%)within Flinders Chase National Park; one within Seal Bay Conservation Park; and four within other large blocks of scrub that were contiguous with reserves. Therefore bush stone- curlews were recorded at 107 of I l4 sites surrounded by agricultural landscapes. The 109 sites where bush stone-curlews \üere recorded were spread widely across the island (Figure 2.2). Ofthese 109 records only two occurred within reseryes, indicating that these birds were primarily using the agricultural landscape. The call-playback survey technique proved to be effective and efficient. Where birds were present, 73%o responded within the first five minutes of the survey, 160/o ftrst responded within l0 minutes and,Ilyo first responded in the last five minutes (i.e. within 15 minutes; Figure 2.3). The results of the re-surveys for three transects were generally consistent with the first survey (Table 2.3), andcombined with the original survey the response rates for the three time intervals (Figure 2.3). after playing the calls was 74o/o,l4Yo and l2o/o at 5, 10 and l5 minutes respectively This indicates that 740/o of the birds that did respond were detected within five minutes, 880/o were detected in 10 minutes, with the remaining l2o/o were detected within 15 minutes. 21 Table 2.3. Summary of call-playback survey results for bush stone-curlews Burhinus grallarius along 13 survey transects. The total number of sites surveyed along each transect (N) and their locations (within a reserve - R, or agricultural land- A), is given along with the number of sites where bush stone-curlews *.r. pr...nt or absent. Where a transect incorporated sites in reserves and agricultural land the birds were generally absent at the reserve sites but present at the agricultural sites. Most surveys were undertaken between September and December 1995, and three were undertaken in July 1996. Eleven of the transects v/ere surveyed over l-2 nights and the remaining two transects were suryeyed over three or more nights. All surveys were conducted between dusk and 2am. Transects Al, B and C were re-surveyed in spring 1996. 1995 Surveys 1996 Surveys Transect N R A Absent Present Absent Present A1 11 ll 0 10 1 9 2 11 7 4 7 4 A3^2 6 6 6 A4 7 1 6 I 6 A5 4 4 4 a B l3 2 1l 2 l1 J 10 C 16 I 15 2 t4 2 l4 D t7 t7 8 I 8 E 22 1 2l 4 18 F l5 l5 15 G t2 t2 I 1l H 5 5 0 5 I 8 8 0 8 Totals 147 33 ll4 36 77 16 58 28 Figure 2.3. Frequency of response times to call playback surveys by bush stone-curlews Burhínus grallørius on Kangaroo Island. Frequency of response times to the call-playback surveys undertaken along 13 transects across Kangaroo Island are given for each of the f,tve minute blocks of 'listening' time. Once a response was obtained the survey was considered finished. N: 109. 80 73 74 70 60 o o 250 o o*¿o ú. b30 s20 16 14 11 12 10 0 51015 Response Times (minutes) aOriginal Survey AOriginal and Re-surueys Combined 29 Community member surveys As shown in Table 2.2 only 38 (8%) of the questionnaires distributed to all landholders via the general mail-out of the Landcare Newsletter were returned and only eight (7%) of survey forms distributed directly to landholders via their Landcare group were returned. All landholders that responded had heard andlor observed bush stone-curlews on their properties, and these records are incorporated into Figure 2.2. The results of the questionnaire can be seen in Appendix 2. 2.3 DISCUSSION 2.3.1 Effectiveness of survey methodology The call-playback survey technique developed for this study provided a simple and effective method for surveying large areas of the island. As indicated similar techniques have been widely used to help with the detection of species that are cryptic or elusive, or otherwise difficult to observe (Marion et al. l98I). In the case of bush stone-curlews the majority of the responses (8g%) were obtained within the first 10 minutes of each survey (Figure 2.3), and three transects \Mere re-surveyed with similar results (88% of responses within 10 minutes) indicating that the technique produces repeatable data. Therefore the data obtained provide a good base-line from which future surveys can be undertaken to determine if the Kangaroo Island population of stone- curlews remains widespread and common. Most landholders on Kangaroo Island were familiar with the birds (pers. comms.), which is not surprising considering their distinctive vocalisations and appearance. However, the response from landholders to the request to undertake 'listening' surveys for the birds at dusk was quite poor and did not reflect the effort required to seek the involvement of these people. The questionnaire also had a similar retum rate, however, because it was circulated to a wider audience (i.e. all landholders) the total number of returns was greater. Future surveys should focus on the use of questionnaires only with increased effort applied to encouraging landholders to return these. Strategically targeting landholders from areas where data are limited using telephone calls could also be effective. All responses indicated that bush stone-curlews were present, and these records complemented the records obtained from the call-playback surveys, particularly as many came from areas between the transects. 30 2.3.2 Historical perspective The historical records presented in Figure 2.1 clearly demonstrate the range contraction and decline of bush stone-curlews in South Australia. As indicated, ornithologists and naturalists noted this decline earlier this century in the l92}s and 1930s. They circumstantially athibuted the decline to the fox, which was extending its range across South Australia at the time that the bush stone-curlews were becoming scarce (Rolls 1984). Habitat modification through broad- acre clearance and grazing was also considered a major factor in the birds decline. The relative importance of each of these threatening processes is difficult to assess. However, the results of the surveys on Kangaroo Island suggests that the distribution and abundance of the birds has increased since the initial clearance of vegetation. This provides circumstantial evidence to support the notion that foxes, which are not present on Kangaroo Island, impacted heavily on these birds and had a greater impact than vegetation clearance per se. 2.3.3 Distribution on Kangaroo Island and broad habitat preferences Mary Ann Wilson moved to Hog Bay River in 1879, and recalled the 'plaintive cry of the curlews at night' when referring to the isolation (Nunn 1989). This indicates that the birds were present on the island during the early period of settlement. Very little vegetation would have been cleared by 1879, so it is probable that small numbers of stone-curlews did occupy suitable habitat on the island prior to settlement. The birds occurred on the Fleurieu Peninsula and other adjacent areas of mainland (see Figure 2.1), and they could have flown across to the island in search of suitable habitat. Large scale wildf,rres may have provided windows of opportunity for the birds, by opening up otherwise unsuitable vegetation, and encouraging birds to 'visit' from the mainland. Little is known about the condition of the vegetation on the island whilst Aborigines inhabited it. During that period regular buming may have made the habitat more suitable. As expected this study confirmed that bush stone-curlews are widespread and common on Kangaroo Island. The results of the call-playback surveys were particularly useful in that they clearly demonstrated the broad habitat preferences of the birds. In particular the birds were absent from only 11 (10%) sites surveyed within the agricultural areas, and four of these sites were located within large blocks of native vegetation that rüere contiguous with reserves. Conversely, of the 33 sites surveyedwithinreserves, bush stone-curlews were onlyrecorded at 3 3l (9%). Therefore, on a broad-scale, the birds are clearly favouring agricultural land over large areas of remnant native vegetation. This result raises two important questions. First, were bush stone-curlews present on Kangaroo Island before settlement and the advent of vegetation clearance? Secondly, if the birds are preferentially using a modified environment does this provide supporting evidence for the detrimental impact of foxes on the mainland? Bush stone-curlews are considered to prefer lightly timbered open forest and woodland, or partly cleared farmland with remnants of woodland, with a ground cover of short sparse grass and few or no shrubs (Marchant and Higgins 1993, Johnson and Baker-Gabb 1994). This suggests that the vegetation clearance that has occurred on Kangaroo Island has improved the habitat for these birds by artificially creating open woodland and grassland habitats favoured by the birds. Also, despite extensive clearance, the percentage of remnant vegetation that remains within the agricultural areas on Kangaroo Island (2lyo, Ball and Camrthers 1998) is much higher than in equivalent areas on mainland South Australia (2-l0o/o, Paton et al. 1999). This situation may favour the birds by providing more potential sites for roosting and nesting. A greater percentage of vegetation has been cleared within the agricultural districts on the mainland, and remaining remnants are typically small with large perimeters compared to Kangaroo Island. However, the habitat within these agricultural areas can be considered relatively similar, with remnants isolated from each other and surrounded by cleared land. This suggests that habitat clearance within agricultural districts may not have been the major factor that led to the decline of stone-curlews on the mainland. This is supported by their decline in the arid zone, where vegetation clearance has not occurred. Although circumstantial, evidence from the arid zone and Kangaroo Island fuither points towards the fox as being the major problem on the mainland. This may also help explain the decline that has occurred within the northern parts of the state where habitat modif,rcation has occurred on a much finer scale and broad-acre clearance has not occurred. The relationship between this population and mainland populations is not known. It was once thought that all the bush stone-curlews on the island 'commuted' from the mainland (Marchant and Higgins 1993), and while this is clearly not the case, prior to settlement there may have been some transfer between the island and the mainland. Therefore the Kangaroo Island population 32 should be considered as a source of birds for reintroductions onto the mainland. Opportunities for reintroductions are increasing as feral pests are being removed from more and more areas through programs such as Operation Bounceback in the Flinders Ranges (see DePreu 2000), and the Arid Ecosystem Project at Roxby Downs. 2.3.4 Conclusions Bush stone-curlews are widespread and apparently abundant on Kangaroo Island, and so clearly the Kangaroo Island population is the most viable population in South Australia, and probably the whole of southern Australia. As a consequence this population has very high conservation 'With significance. the lack of foxes and controls on native vegetation clearance it is anticipated that this population should remain viable in the longer-term. However, continued monitoring should take place in order to detect any major changes. Repetition of the call-playback surveys will provide an efficient means for monitoring the population, and could be supported with the use of questionnaires. Not all transects would have to be surveyed, particularly those located within NPWSA reseryes, where preferred habitat does not occur' JJ CHAPTER 3 SIZE OF HOME RANGES AND MOVEMENTS OF BUSH STONE. CURLE\ilS BARHINUS GRALLARIUS OI{ KANGAROO ISLAND 3.0 INTRODUCTION Bush Stone-curlews were once widespread and abundant across the mainland of South Australia but are now classified as endangered following a major contraction of their range and population decline (see Chapter 2). In contrast bush stone-curlews are relatively common on several offshore islands, and Kangaroo Island in particular provides a sanctuary for a large number of these birds. The large size of Kangaroo Island and the absence of foxes makes it the last stronghold for the species in southern Australia. An understanding of how a species uses the available habitat, both spatially and temporally, is critical to demographic and ecological studies (Quin et al. 1992) and to the management of the species. The social organisation and home range size of bush stone-curlews has not been specifically studied but some information is provided from studies by Bright (1935), Bedggood (1977), Anderson (1991) and Johnson and Baker-Gabb (1994). Bush stone- curlews are found singly, in pairs, or as families with l-3 young. During the non-breeding season, some birds remain as resident pairs (Johnson and Baker-Gabb 1994) while others form small flocks, typically of 5-10 individuals (in southern Australia). As the breeding season approaches the flocks separate as birds re-establish territories. Pairs often nest repeatedly near traditional roosting and/or nesting areas. Johnson and Baker-Gabb (1994) found that in the past, in northern Victoria, four breeding pairs would occupy an area of approximately 290 hectares (the size of original farms, approximately one mile square), although today only one pair or fewer occupy the same area. During the breeding season territory sizes have been estimated at between l0 and 25 hectares (Schodde and Mason 1980, Johnson and Baker-Gabb 1994, Wilson 1989) and birds remain within this area for up to eight weeks (Johnson and Baker-Gabb 1994). Outside the breeding season the birds move within a loosely defined home range, with Johnson and Baker-Gabb (lgg4) suggesting the size of which is probably determined by availability and distance between suitable roosting areas. which are typically associated with remnant vegetation' In Victoria, Johnson and Baker-Gabb (1994) estimated that the diumal home lange was up to 250 hectares per bird, but suggested that the noctumal home range would be much larger. In 34 suburban Brisbane, Anderson (1991) noted that bush stone-curlews moved well beyond their daytime roost when not breeding, and may have foraged over 95 hectares, but this was probably reduced to 4l hectares when the birds had dependent young. Other observations in Victoria indicated that one pair roosted in five favoured timbered areas within only 12 hectares, and another pair occupied a roost area of less than one hectare all year round (Johnson and Baker-Gabb t994). Another family of bush stone-curlews was usually located within one kilometre of its nest and rarely ranged more than two and a half kilometres from this location (Johnson and Baker-Gabb t994). All of these observations have been made in areas with foxes, which may cause disturbance and influence home range sizes and their use. Clearly, whilst some data are available on social organisation, most have come from a couple of studies. All estimates have also been based on direct observations of the location of birds, especially during the day, and very little data on noctumal movements have been collected. This study aimed to answer the following questions: 1. What are the sizes of home ranges used by bush stone-curlews on Kangaroo Island? 2. How do bush stone-curlews use their home range areas? 3. Are there consistent pattems of home range use by different birds? 4. What factors might influence the locations, arïangements and sizes of home ranges? 3.1 BACKGROTJND INFORMATION 3.1.1 DefTnition of home range A wide range of activity areas are quantified and defined in studies of temporal and spatial use of habitat by animals. These include home area, home range, territory, fotaging area (Quin et al. 1992) and breeding territory (Johnson and Baker-Gabb 1994). The most commonly used is the concept of home range as defined by Burt (1943). Burt (1943) defined the home range of an animal as 'that area traversed by an individual in its normal activities of food gathering, matin g, and caring for young. Occasional sallies outside that atea, perhaps exploratory in nature should not be considered as part of the home range'. However, there is no consensus regarding the most appropriate definition of home range or the most reliable technique for estimating the size of home ranges (Dixon and Chapman 1980, White and Garrott 1990, Quin et al.1992). Burt's (1943) definition suffers from the lack of a temporal component (eg Harris et al. 1990), as the use of space is likely to vary according to season, population density and resource 35 availability (Quin et al. 1992). Another problem with Burt's (1943) definition relates to the key word 'normal'. Home range is def,rned as the area where an animal 'normally' moves, and not the total area, and therefore objective criteria are required to select those movements that are normal (White and Garrott 1990). White and Garrott (1990) note that in the literature two criteria are typically used: subjective evaluation of the researcher or a probability level. The second criterion has led to a more precise probabilistic definition of home range, as has the need for performing statistical analyses of home ranges (Seaman and Powell 1996). The term 'utilisation distribution' has been developed to take into account the fact that animals rarely use their entire home range with equal intensity (Dixon and Chapman 1980). The utilisation distribution is a 'probabilistic model of home range that describes the relative amount of time that an animal spends in any place' (Seaman and Powell 1996). Typically the area that contains the animal 95o/o of the time is considered its home range size. Whilst this is arbitrary, and has no biological basis, it is at least objective and repeatable (White and Garrott ree0). For the purposes of this study the traditional term'home range'is used because the overall size of the areas used by the bush stone-curlews is being investigated' 3.1.2 Analysis of home range sizes Numerous authors have compared and discussed the various options available for estimating the areas of home ranges of animals (see Kenw ard l98l , White and Garrott 1990, Qtin et al ' 1992, Troy and Coulson 1993, Seaman and Powell 1996, Comport et al. 1996). Analysing the size of home ranges is a numerical estimation, but the map of locations is still a very important tool because practical information contained in the map may be lost with the numerical estimate process (V/hite and Garrott 1990). Unfortunately there is no single or preferred estimator as all of the estimators have their faults. The oldest and simplest technique for estimating home range areas, the Minimum Convex Polygon (MCP) method, connects all of the outer-most points to form a convex polygon and calculates the arca within. Whilst this technique is simple and allows for flexibility of shape the home range size increases indefinitely as the number of locations increase, and also the total arca is calculated, not the 'normal' area that is used by the animal, as discussed above (White antl Garrotl. 1990). 36 More complex bivariate normal models such as the Jennrich-Turner Estimator (Jennrich and Turner 1969) have followed the MCP estimator. These models assume that animals move randomly about their home Íange, with the most probable location being the very centre. The animal is therefore using its space as a bivariate normal model. An ellipse (e.g. 95%) is then calculated around the centre and the area of the ellipse estimates the home range size (White and Garrott 1990). However, bivariate normal models are not likely to accurately describe the movements of most wild animals. Wild animals will move about their home range with purpose in order to obtain the necessary resources, and there is no biological reason why an animal should be expected to spend most of its time at the centre of its home range. Despite this, White and Garrott (1990) recognise that the use of these models is still worthwhile as the concept is practical and availability of computer programs makes calculation simple. In response to some of the problems with the bivariate normal models a number of non- parametric estimators have been developed (eg Fourier Series Smoothing, Anderson 1982; Harmonic Mean, Dixon and Chapman 1980; and Kernel, Worton 1989). Details on how these techniques treat the data are included in a wide range of literature (e.9. see Kenward 1987, 'White and Garrott lgg0, and Seaman and Powell 1996). Problems common to all nonparametric methods are that the time series nature of the data is not considered and none of the models incorporate an associated confidence level. Therefore no indication of the precision, and therefore the usefulness, of the estimation is available (White and Garrott 1eeO). To date it has been commonly asserted that home range estimators require that locations for estimating home range are statistically independent to obtain an unbiased estimate (Swihart 'White and Slade 1985, Harris et at. 1990, and Garroff 1990). Independence of observations is primarily concerned with the time interval between successive locations. White and Garrott (1990) indicate that generally two locations will be independent if the time between them is enough for the animal to move from one end of its home range to the other. If two points are not independent they will not contribute two 'complete' locations because one of the locations can be used to make a reasonable guess of the other (White and Garrott 1990). Howevet, more recently De Solla ef al. (1999) examined whether home range estimators based on kernel densities required serial independence of observations to ensure unbiased estimates. Their results indicated that independence of fixes is not as important as previously thought and that home range size was better represented by autocorrelated observations. 37 In the following analyses of home range sizes I used Minimum Convex Polygon, Harmonic Mean and the Kernel methods and made comparisons between these. 3.1.3 Study sites The study of home ranges was conducted at two sites in the south-west of Kangaroo Island - Flinders Chase National Park Headquarters (FCHQ) and an agricultural property, 'KB Downs', located approximately 1Okm to the east (Figure 3.1) along the South Coast Road. The study area at FCHQ primarily consists of a cleared lowland area and an intermittent swamp adjacent to low consolidated dune ridges. 'KB Downs' is gently undulating with small limestone ridges and stony swales covering much of the property. Several small swamps and associated low-lying areas can be found on the western parts of the property, and small areas of laterite soils associated with the Island's plateau are also present. The vegetation at both sites is quite variable and includes forest, woodland, mallee scrubs, grasslands and heath vegetation. A detailed description of the vegetation found within Flinders Chase National Park can be found in Department of Environment and Planning (1986), and this provides a good overview of the vegetation found at both sites. A summary is also provided in Chapter 1. 'KB Downs' is bordered by Flinders Chase National Park to the west, the South Coast Road to the north, Hanson Bay Road to the east, and the Southern Ocean (Figure 3.1). Much of the southem half of the property contains original vegetation communities and the remainder consists of cleared pasture, with smaller patches of remnant vegetation. Clearance on this properfy took place much more recently than at FCHQ. During the course of the study 'KB Downs' was de-stocked as the property was purchased for the purpose of maintaining and enhancing its conservation value. Despite the de-stocking, the pasture is kept short by abundant tammar wallabies Macropus eugenii that shelter in the large areas of vegetation during the day. The areas of improved pasture have not had any super-phosphates added in recent years, although clover, Triþlium species, is still present, and cape weed Arctotheca calendula grow prolifically on these paddocks. 38 Figure 3.1. Locations of study sites for home range and movements study on bush stonecurlews ßurhìnus grallarius. I NPWSA Reserves Nalrve Vegetation 0 10 20 Kilometres A H 39 3.2 METHODS 3.2.1 Capturing the birds Bush stone-curlews were captured and fitted \Mith backpack radio transmitters between July 1996 andJune 1998. A minimum of two people were generally required to capture the birds. The birds were located by driving ('KB Downs') or walking (FCHQ) around the cleared areas birds and paddocks while searching with a Lightforce 100V/ spotlight. With experience the metres were readily observed in the light and were quite easy to approach. Once within 20-30 and one person proceeded towards the bird on foot whilst another controlled the carlspotlight to ensured that the light remained on the bird. A long handled net was placed over the birds capture them. This technique was used successfully in a variety of weather conditions and with various moon phases, although it was particularly successful on dark and windy nights' flew On these nights birds were generally reluctant to fly, and when they did they usually only they a short distance. Occasionally birds were caught without a net, particularly when walked into vegetation and were unable to navigate through it with the light on them' 3.2.2 Radio-transmitter attachment and banding the Radio-transmitters were supplied by Bio Telemetry Tracking (Australia)' The life of radio-transmitters was approximately 9 months. Each radio-transmitter with harness weighed on the approximat ely 34 grams, which represented 4-6% of the bird's body weight, depending weight of the bird (range 550gm - 880gm). Of the f,rfteen birds fitted with radio-transmitters only two had transmitters that weighed over 5Yo of their body weight' Two techniques for attaching transmitters were tried on captive bush stone-curlews at the parndana V/ildlife park. The transmitters were initially supplied with a shoelace hamess that chest' consisted of three loops, one for under each wing and one for across the front of the in the chest This hamess proved to be unsuitable as the bird managed to get its beak entangled strap. The revised harness employed 4mm wide elastic to improve freedom of movement, hamess used on and did not include a chest band (Figure3.2). This harness was similar to the malleefowl Leipoa ocellata by Benshemesh (1992). A single elastic strap was placed under backpack' each wing such that the transmitter sat in the middle of the bird's back, like a preening quickly covered the transmitter with feathers and hid it from view. It was necessary the to fit the harness firmly so that the transmitter was not free to move around too much on 40 Figure 3.2. The harness design and attachment of radio-transmitters on bush stone- curlews Burhínus grallørius. The transmitter and hamess system is shown along with the position of the transmitter on the bird. Each transmitter weighed 34g, which was less than 5Yo of body weight for l3 of the 15 birds captured. The sketch below above was drawn from a photograph taken just after the transmiúer was placed on it, and therefore the transmitter has not yet been covered by preening, and as ã result appears to be sitting high. Following preening the transmitter soon becomes covered in feathers and settles closer to the back. I \ t I çr i1',i', "' '" .: u 0r:::'' :a i t,E:ruo, ': fil4 t I + ,l .ì,¡.;ri:'., i: ì' i'*ii'É':i'.1 4l bird's back, but not too tight so as to restrict movement. To do this the elastic harness was pulled firm and then the transmitter was gently 'wiggled' to release a little of the tension, before being tied off. The knot was secured with Supaglue@. Similar backpack style transmitters and harnesses have been used on a number of other birds including owls (Stephenson et al. 1998, Call et at. 1992, Foster et al. 1992), ducks (Pietz et al. 1993, Garrettson et a1.2000), cock pheasants (Johnson and Berner 1980), grouse (Marks and Marks 1987) and crows (Stouffer and Caccamise l99l), and as indicated above, malleefowl (Benshemesh 1 992). All birds captured were also banded with size l0 steel bands from the Australian Bird and Bat Banding Scheme (ABBS), along with one plastic colour band above the metal band on the left leg and two colour bands on the right leg. The colour band placed above the steel band was covered with reflective tape of various colours to assist with locating the bird again at night. The ABBS have recommended size 9 steel bands, however, these were tight on the first few birds banded, so size 10 bands were used instead. The top and bottom edges of the bands were also smoothed with a file to ensure that the sharp edges did not aggravate the leg and foot scales. 3.2.3 Radio-tracking Procedure Radio-tracking was undertaken with a hand-held antenna mounted with a compass, and took place on foot at FCHQ and with the assistance of a car at'KB Downs'. The triangulation technique was used to obtain the locations (fixes) of the birds (see Garrott et al' 1986, Kenward lg8l, Schmutz and White 1990, V/hite and Garrott 1990, and Saltz 1994)' Two junctions) compass bearings were obtained from known points (e.g. isolated trees, paddock and these were plotted onto transparent sheets overlayed on enlarged aerial photographs (1:5,000) to determine the approximate location of the animal. If the intersecting angle of the two bearings was <600 or >1200 a fuither bearing was obtained from another location. This helped to ensure the precision of the location was as high as possible. To quantify each location the grid from the l:50,000 topographic map series was drawn onto each photo, and a finer scaled grid of 25x25m was copied onto the transparent sheets. With the use of this grid the position obtained from the compass bearings was recorded as northings and eastings, consistent with full Australian Map Grid (AMG) references. This allowed the data to be directly imported into Geographic Information System (GIS) packages for mapping and analysis pu{poses. Positions were recorded to the nearest five metres, although it is 42 acknowledged that this resolution is likely to be greater than the accuracy possible using the triangulation technique. Inherent in the radio-triangulation technique is a degree of error, with the level of precision depending upon three main factors: the variance around the bearings obtained; the distance to 'White the transmitter; and the intersection of the angles (Saltz 1994, Schmutz and 1990, Garroff et at. 1986). To produce an effor measure all factors must be considered (Saltz 1994), although Saltz (1994) reported that of 69 papers reviewed 29% did not report enot, and 48o/o provided some information on the above three factors. Whilst I did not specifically measure error, validation of some fixes was undertaken by making direct observations of the locations of the birds. Radio-tracking took place at irregular intervals over the study period. Discontinuous tracking (Harris et at. 1996) was conducted on single nights or for up to five consecutive nights' At least two fixes were obtained for each bird per night and up to ten fixes were obtained when tracking took place throughout whole nights (16 bird-nights). Consecutive fixes for the same bird were not obtained at time intervals of less than 20 minutes. This minimum time separation between fixes was considered ample for bush stone-curlews to fly across their entire home range, which is considered adequate to provide independent fixes (White and Garrott (1990). Although, as indicated above, recently De Solla et al. (1999) have disputed the need for observations to be independent, suggesting that researchers should simply maximise the number of observations whilst maintaining constant time intervals to increase the accuracy and precision of their home range estimates. A maximum of seven, but usually three or four birds were tracked at any one time. It was diff,rcult to maintain constant time intervals because the time between fixes depended on the time it took to travel between sites, and to locate or re-locate the birds. All fixes were entered into a Microsoft Access database for ease of data storage and handling. For simplicity diurnal fixes will be referred to as roosts and noctumal fixes as foraging locations. In the case of the noctumal fixes it is acknowledged that the birds may not have been actively foraging at the time that the fixes were obtained. 3.2.4 Calculation of home range sizes and quantifying movements The computer package RangesV (Kenward and Hodder 1995) was used to estimate home- range atea. The AMG references determined for the locations of the birds were imported 43 directly into the package along with the date and time. As outlined above three home range analysis techniques were employed: - (1) Minimum Convex Polygon (MCP, see Southward t978); (2) Harmonic Mean (HM, see Dixon and Chapman 1980); and (3) Kernel method (K, see'Worton 1989, Silverman 1986, Seaman and Powell 1996). Spatial use of home ranges was investigated by measuring the 'foraging distances' for each bird. Foraging distances are defined as the distances between roost sites and foraging locations and were generally only measured on the days when successive roost and foraging fixes were obtained. Additionally, for those birds that always used the same roost area, foraging distances were determined for all foraging f,rxes. If birds appeared to be tending eggs (based on their location and lack of movement) distances v/ere not included. The frequency of the foraging distances (in 100m intervals) were determined for each bird, and these distances were also plotted against the week of the year in which they were recorded (i.e. week I : first week in January) to investigate temporal pattems of home range use. 3.3 RESULTS Bush stone-curlews had not previously been radio-tracked and this study has confirmed that it was possible to employ this technique. Fortunately the birds were relatively easy to catch, with dark and windy conditions proving to be very conducive to catching the birds, although with experience it was possible to catch some birds on calm moonlit nights. The methodology employed here should be successful with other populations of the birds if similar work was to be undertaken elsewhere. 3.3.1 Details of the radio-tracked birds A total of 15 birds was captured and fitted with radio-transmitters between July 1996 and June 1998. Three birds were captured at FCHQ and!2 at 'KB Dov/ns'. Radio-tracking occurred throughout this period and continued until February 1999, when the last active radio- transmitter lost power. The sex of the captured birds was not determined because there were no obvious morphological differences between the sexes (Marchant and Higgins 1993). Age was also difficult to determine, however, it was possible to assign the birds to two age classes (1't year jurreniles and acl¡lts - see Tahle 3.1) hased on their weight and moult. This was particularly 44 Table 3.1. The weights and age-groups of the bush stone-curlews Burhinus grøllørius that were radio-tracked. All weights are in grams. Only two age classes were defined, adults (A) and juveniles (J), due to difficulty in determining more specific ages. Age-class was based on weight and moult. In the post-breeding season juveniles had lower weights and a full set of new ptimary feathers, whereas adult birds were undertaking a post-breeding moult. At other times weight was used to separate the age-classes. *The juvenile was not included in the calculation of mean weight' Bird V/eight at Age-class Capture FCI 640 A FC2 110 A FC3 550* J KBl 790 A t<82 740 A KB3 765 A KB4 820 A KB5 735 A KB6 690 A KB7 760 A KB8 775 A KB9 115 A KBlO 880 A KBI l 765 A KBI2 115 A Meants.d. 746¡79 45 juveniles reliable early in the post-breeding season (approximately December to April) when had lower weights and a full set of new primary feathers, whereas adult birds were heavier and were undertaking a post-breeding moult of primary feathers. For this study adults were deliberately targeted, and whilst numerous juveniles were also captured and banded, they were not fitted with transmitters, with one exception. One juvenile was captured at the same time as one of its parents at FCHQ, and was tagged. The average weight of all the radio- tracked birds was 746t79s.d. g. (range 550-880g; see Table 3'1). Five of the ten birds were subsequently recorded breeding (FCl & FC2, KB8, KB9 & KBl0) and another bird (KB4) was assumed to have bred based on observations of its movements and home range size. KB4 was regularly flushed from the same roost area with another bird. However, it was difficult to approach this roost area without being observed first, and the rocky ground made locating eggs or chicks extremely difficult. All remaining birds were not recorded breeding and were apparently not paired with another bird. 3.3.2 Timing and duration of radio-tracking The timing and length of the radio-tracking periods varied for each bird and to a large extent was beyond *y control (Figure 3.3). The timing of the tracking relative to the breeding season was considered a potentially important factor in determining the movements and home range sizes of the birds. The breeding season was broadly defined as the period when the have eggs of any birds were observed (from July to December), although some chicks would remained dependent on their parents after this period. Within this broadly defined breeding (Figure season the radio-tracked birds were recorded with eggs in October and November 3.3). However, it is possible that not all breeding attempts were discovered' Several birds FC3), were predominantly tracked during the non-breeding season (K81, KB2 and KB7, and whilst the remainder of birds were predominantly tracked during the breeding season, or over both seasons, and this is considered when interpreting the data. The total number of fixes obtained for each bird ranged from 7 (KB6) to 202 (KB5) (Table 3.2). The birds were tracked over periods of 26-510 days and each bird was located on between I and 37 nights (Table 3.2). At least half (mean 68.5úYo, rùrlge 56%-77%) of the fixes were obtained at night for the 10 birds for which home t^nge sizes could be estimated. The birds that were tracked for less than 10 nights were those captured at the very beginning of the study (KBl and KB2) when methods were being trialed, or those that dispersed (KB3) 46 Figure 3.3. The timing and length of radio-tracking periods for each bush stone-curlew Burhinus grallarius that was radio-tracked. Solid bars indicate the period over which each bush stone-curlew was radio-tracked. The months when eggs were observed (i.e. the broad breeding season - July to December) are shaded. The month in which the study birds were observed incubating eggs is indicated with an E. 1996 1997 1998 1999 JFMAMJ J F MA MJ JF FC1 E tc2 E FC3 I KB1 KBz KB3 KB4 KB5 KB6 I KB7 KB8 E KB9 KBlO E KB11 KB'12 I 47 Table 3.2. Radio-tracking effort and number of locations obtained for each bush stone- curlew Burhínus grallarius. The date when each bird was captured and the last date each was located is given along with the length of time that each bird had an active transmitter, and the number of nights when fixes wère obtained. N : total number of fixes; N(d) : number of roost (diurnal) locations; N(n) : number of foraging (nocturnal) locations. Bird Capture Last Date Total Time No. of N N(d) N(n) Date Located (days) Nights Located FC1 1117196 18t2l97 216 1l 75 32 43 FC2 3n2196 27t4198 510 24 155 48 107 FC3 3lr2l96 18t8l97 258 t6 It 30 43 KBI 2lt0l96 2slsl97 235 5 l8 10 8 T<82 t2lt2l96 615197 t44 4 15 6 9 KB3 |7197 2711197 26 I 9 4 5 KB4 y7197 1913l98 261 t1 t4l 36 105 KB5 U7197 1 s/10/98 47r 37 201 59 142 KB6 23t8197 15ll0l97 53 I 1 6 1 KB7 2812198 r6t7l98 138 t3 60 22 38 aa KB8 19lsl98 rslU99 24r JJ 162 4l t2t KB 9 r6t6l98 t5lr0l98 tzl 19 85 2l 64 KB t0 2216198 18l2l99 241 36 151 34 tl7 KB 11 2216198 17lt2l98 n8 22 86 24 62 KB t2 2216198 418198 43 5 22 8 l4 48 or \ryere lost and presumably dispersed (KB6 and KB12). The data-set obtained for these five birds was too small to calculate home range sizes, although their patterns of movement contributed important information. 3.3.3 Comparisons between home range analysis techniques The three home range analysis techniques I used each produced varying estimates of home range size and home range boundaries (Figures 3.4a and 3.4b). The spatial arrangement of fixes, which often reflected the arrangement of habitat (pers. obs.), and the density of fixes, influenced each analysis technique differently. Although I aimed to select one method that adequately represented the data for all birds, this proved diff,rcult. A comparison of the estimates for 85o/o, 90o/o and 95% of home ranges showed that the 90% estimates most accurately portrayed the home range based upon the distribution of the fixes and an understanding of the available habitat. For the breeding birds FC2, KB4, KB9 and KBIO the three analysis techniques produced relatively similar estimates of home range sizes and boundaries (Figure 3.4a), although HM estimates were typically greater as a result of the boundaries 'ballooning' out from the fixes. This resulted in too much unused habitat being incorporated within the home range boundaries (pers. obs). The only exception to this was for FC2, where the MCP technique included one outlier that extended the range considerably, also resulting in a large portion of 'unused' habitatbeing included within the range (Figure 3.4a). However, as indicated above, the size estimate from the HM technique was still slightly Iarger for this bird. For these four birds the K estimate appeared to provide the most accurate representation of the data from a biological perspective (Figure 3.4a). For FCI and KB8 all techniques had difficulties in adequately representing the data (Figure 3.4a) due to the spatial pattem of the frxes, which reflected the arrangement of the habitat. The MCP estimates were unduly affected by outliers and as a result too much 'unused' habitat was included in the ranges, particularly for KB8. Both K and HM estimates 'ballooned' out considerably from the fixes for FCl, and although these appeared to reflect the data better than the MCP estimates, both also included 'unused' habitat. Despite this, all three estimates of home range size were very similar for FC1. In contrast the three estimates of home range size varied considerably for KB8, partly because the overall home range was larger for this bird. V/ith KB8 the K boundary estimate produced three separate polygons, and this was not 49 Figure 3.4a: The home range boundaries and sizes (ha) estimated by the kernel (K; solid lines), harmonic mean (HM; dashed lines) and and minimum convex polygon (MCP; dotted lines) analysis techniques for six breeding bush stone-curlews Burhinus grallørius on Kangaroo Island. a 0 - a M=56 =337 =.'+ P=55 CP=445 ''e a \ I \' 1 \ I a iì a I /. a\. oF aa x a "\{ ,,à a a/ .a .a 20ùn 0200m a K=42 q O =120 HM=51 =137 MCP=49 CP=1Q2 ta .9o. a a t o aþ a I $ a .t a a a o 1'.'. t a I a a tr a olþ a a ..?% aa .\ O \. ¡ a a. to a I 'al a a ? 'o I \- /a O¡ - a 0 200m 0 200m KBlO a =38 K=26 HM=44 HM=43 /,.Fo..- .rr \ MCP=3$ o MCP=31 a. / a ó a l a a a a I a I a .jt I \ I aaa a a a a o oo, \ a \ aa \ q. 'O--* I a a 200m 0 20ùn 50 Figure 3.4b: The home range boundaries and sizes (ha) estimated by the kernel (K; solid lines), harmonic mean (HM; dashed lines) and and minimum convex polygon (MCP; dotted lines) analysis techniques for four non-breeding bush stone- curlews Burhinus grallarius on Kangaroo Island. FC3 K=32 K=285 HM=26 HM=318 MCP=346 -u MCP=33 (. ,+ .rt a fr ü.- O ot' /r. a a aa a a a \ a a ti I a jr I oo , t a a I - O¡a ..¿ I -t aa , Þ ¡+ 500m 0 500m I K=877 a HM=703 a -7 P=312 MCP=727 , a q\ a ;) tJ. a ) a -, a a at' ?ß ir a a ít ¡O a a aa a a a a .¡ a a a a 3t a ...Íi.. a a ;j a a a aa a 0 500m 0 500m I I 51 considered a biologically accurate reflection of the use of the area by this bird, which also used the intervening areas. Therefore the HM estimate produced a more realistic estimate for this bird, although this also produced a boundary that 'ballooned' into unused habitat. The three home range estimators for the four non-breeding birds also produced various results (Figure 3.6b). For KB5 and KBl1 all three techniques were relatively similar, although the differences in estimates of home range boundaries for KB I I resulted in a relatively wide range of size estimates due to the large area involved. For FC3 all three techniques produced similar home range size estimates, however, the boundaries varied considerably, with the HM estimate producing two polygons, The K method appeared to produce the best results for FC3. Both the K and HM techniques also produced multiple polygons for KB7, and this was also not considered a biologically accurate reflection of the use of the arca by the birds þers. obs.). Therefore the MCP technique produced the most biologically correct estimate of the home range boundary for KB7, although this resulted in a relatively higher home runge size estimate due to the inclusion of an outlier. An analysis of variance between the estimates of home range sizes for each technique for all birds was undertaken and as expected there was no significant difference between estimates (ANOVA: F:0.003, p<0.99, dt2,6). Based on this, and interpretations of the home range boundaries based on field observations, as outlined above, the K estimate appeared to produce the best results. As indicated, in general the boundaries produced by the HM appeared to 'balloon' too far beyond the actual fixes and therefore included too much unused habitat (pers. obs.). Also the boundaries produced by MCP tended to incorporate outliers, with the same effect. However, for the breeding bird KB8 and the non-breeding bird KB7, the HM and the MCP techniques produced the best results respectively. Therefore, the estimates of size referred to in the next section are the K estimates, except for birds KB7 and KB8 as indicated above (Table 3.3). 3.3.4 Home range sizes and use of home ranges by individual bush stone-curlews In this section, for each individual bird with sufficient datal provide a summary of the home range sizes, spatial roosting pattems and fidelity to roost sites, and foraging distances from roosts (see Section3.2.4). These analyses allowed for a comparison between pattems of use of home ranges by the different birds. Figures showing the home ranges, locations of fixes and habitat are presented for birds that used the same parts of the study sites, and therefore the 52 birds shown on the same figures were not necessarily radio-tracked concurrently (refer to Figure 3.3). Breedins birds FCl FCl was the first bird to have a radio-transmitter attached. The home range estimate for this bird was only 56 ha (Table 3.3). FCl was always observed roosting with another bird, and formed one of the two breeding pairs at FCHQ. This bird occupied the westem side of the available habitat at this site (Figure 3.5) and was resident throughout the tracking period, between July 1996 and February 1997. Alfhough relatively little data were collected for FC1, most available areas of foraging habitat were used during the tracking period (Figure 3.5). FCI used seven roost areas that were located close to the edge of cleared areas (Table 3'4; Figure 3.5), although only a few of these were used regularly. Not surprisingly most foraging distances were less than 800 m (Figure 3.6a), primarily reflecting the small area of available foraging habitat at FCHQ. No hends in foraging distances over time were apparent (Figure 3.6b), in part probably due to the limited data set. FCI was recorded breeding in a small circular clearing at the western end of its range. FCl appeared to have an almost exclusive home range, with little overlap recorded lvith FC2 (one bird from the other pair at the site)' Unfortunately this bird was found dead in a small clearing approximately 500 m north of its observed home range area approximately seven months after radio-tracking began. FC2 FC2 was also always flushed with another bird and belonged to the second breeding pair of bush stone-curlews at FCHQ. During the 17 months that radio-tracking occurred (I was able to replace the original transmitter), FC2 was recorded within a relatively small home range area of 42ha (Figure 3.5 and Table 3.3). Throughout this period the bird used its home range very consistently, roosting in old regrowth vegetation at the western part of its range, and foraging in open habitat at the eastern part of its range (Figure 3.5). Only four roost areas were recorded (Table 3.4). Nearly all foraging distances were greater than 400 m (Figure 3.6a) because suitable foraging habitat was at least 400 m av/ay from FC2's roost (Figure 3.5). The bird usually flew directly between roost and foraging areas (pers. obs.). Few foraging distances were greater than 1000 m, reflecting the small area of available habitat (as for FCI). On one occasion FC2 was recorded making an exploratory trip to the south. FCz was caught at the end of the breeding season ancl had at least one dependcnt juvcnile at this 53 Table 3.3. Estimates of home range area for ten bush stone-curlews Burhinus grøllarius using the south-western area of Kangaroo Island. Estimates are for 90% isolines produced by Minimum Convex Polygon (MCP), Harmonic Mean (HM) and Kemel methods. Based on the home range boundaries produced by each method the Kernel estimates were considered to best represent the data for all birds except KB7 and KB8. The preferred estimates are shown in bold. Bird MCP HM Kernel 90% 90% 90% Breeding Birds FCl 55 56 64 FCz 49 5l 42 KB4 39 44 38 KB8 445 337 200 KB9 IO2 137 120 KB10 3l 43 26 Non-breeding Birds KB5 312 390 367 KB7 346 318 285 KBll 127 703 877 FC3 33 26 32 54 FC1 - Kemel home range estimate (90%)= 54 ¡t. O Diumal(Roost)Sites O Noctumal(Fonage)Sites FC2 - Kernel home nange estimate (90%) = 42 ¡. O Diumal(Roost)Sites O Noc{umal(Fonage)Sites FC3 - Kemel home nange estimate (90%) = 32 ¡.. O Diurnal(Roost)Sites O Noctumal(Forage)Sites Landcover I OriginalVegetation I Remnant Vegetation (sparse u/storey) I Regrcwth Vegetation II Sedses . : Revegetation I Pines Cleared Land I Dam r Buildings A N 0 100 2OO 300 400 Metres Figure 3.5 Radio-tracking fixes and home range boundaries for three bush stone-curlews Barhinus grøllarius (FC1, FCz &, FC3) at tr'linders Chase National Park Headquarters, south-western Kangaroo Island, 1996 - 1998. NB (1): FC3 was FC2's progeny and therefore these birds shared the same home range area. Consequentþ some of FC3's fixes (particularly roost sites) are obscured by FC2's fxes. NB (2): Three location points for FC2 are not shown. These were located approximately 0.7 kmto the south, on the road and adjacent cleared line. All six southem most locations were recorded during one night. 55 Figure 3.6a. Frequency of 'foraging distances' for six breeding bush stone-curlews Burhinus grølløríus on south-western Kangaroo Island between 1996 and 1999. 'Foraging distances' are the distance between diurnal locations and noctumal locations (see Section 3.2.4). r FC1 aFC2 ¡ KB4 30 25 20 o c o 1 5 cr= o lr 0 5 0 I ll) (O r CD \t lr) (o l- @ OJ O TN(9SIf)If) r N cÐ + l- @ o) O N NNNNNN ó + ñ.å +,Áó F: ¿ O)O-NCr)*rftf)(ol-@O)i Ì 5 Y YÌ Ì ï 5 5 I r-rrrrrrr NC{NNNó+ñó+^ Foraging Distances (x 100 m) r KB8 ¡ KB9 ¡ KB10 30 25 20 o ç o 5 1 5 ct o II 1 0 5 0 O N CO S t.C) (O l- @ O) O I N CD $ q? A -NCÐ$tO(Ol-@O)tftt¡ll - O-N(f)$rO(Ol-@ -rr-rTr;lqqNc\lNNN (o @ o) ó rrrris-sNNNNNó J ñ ó *,o r'- e - Ñ ó + ^ Foraging Distances (x 100 m) 56 Figure 3.6b. Temporal patterns in 'foraging distances' for six breeding bush stone-curlews Burhinus grøllarius on south-western Kangaroo Island between 1996 and 1999. Foraging distances (see Figure 3.6a) are plotted against the week of the year when they were observed. Week I is the first week in January. FC2 was radio-tracked for 17 months and data for the same weeks in consecutive years are combined. Note scales on the y-ans vary. 12AO (a) FC1 3200 (d) KBsog 2800 1 000 I 2400 800 oQ 2000 g 0 o 96u o 600 o sg 1 600 B F o o 400 o 1200 0 o 800 o$ 240 o I 8 o o f oB o 400 o a 0 0 g i 2000 (b) Fc2 1200 (e) KBs n I o 1 1 600 000 g o o 9O o 800 o 1200 o o o I D 600 800 o g o o 400 8ã 8 ¡ og ooo gB" o o s 400 I s8 .9" 200 Es I I t 0 0 88 a n 16C,0 (c) 800 G KB4 (f) KB10 14C'O o 700 e o 12C,0 600 o s 10C,0 500 I o o (m) 8C,0 o 400 o 6C,0 300 I o I o o 4C,0 0 o 200 3o I 2C'0 o I 100 o B E 0 0 o 4 I 12 16 20 24 28 32 36 40 44 48 52 o 4 I 12 16 20 24 28 32 36 40 44 48 52 Weeks of the Year Weeks of the Year 5l Table 3.4. Fidelity to roost sites for ten bush stone-curlews Burhinus grøllarius. The number of diurnal fixes are compared to the number of different roost sites used by the birds. Roost sites were defined as areas of less than or equal to tha. Only those birds for which home range area estimates could be determined are considered. Bird Total Diurnal No. of Roost Comments Fixes Areas Breeding Birds FCl 32 7 FC2 48 4 . 45 fixes within one 3ha area KB4 36 8 . 23 fixes within one tha area; all roosts within 350m of this site KB8 4l I4 r only 3 sites within the breeding territory (17 roosts); 11 sites used outside breeding territory KB9 2t 10 . only two sites used within the breeding territory a KB 1O 34 J ¡ 32 roosts within one site; the other two <200m from this site. Non-breeding Birds FC3 30 4 . 26 fixes within one 2ha area KB5 59 t9 KB7 22 9 KBl l 24 15 58 time (see FC3). It was recorded breeding in the following season, although this attempt failed. No other breeding attempts were observed, although it is possible some were overlooked. No obvious temporal trends in foraging distances and home range use were observed (Figure 3.6b), probably in part due to the relatively small area of suitable habitat that was available to this bird. KB4 KB4 was captured just prior to the breeding season and was recorded using a relatively small home range of 38 ha (Table 3), in which its roost area was centrally located (Figure 3.7). As a result most foraging distances \Mere less than 500 m (Figure 3.6a). KB4 was usually observed roosting with another bird, although the nature of its roost area made it very difficult for me to approach this bird \Mithout it being a\Mare of my presence. It was considered to be a breeding bird based on the presence of another bird, and its small home range area, despite the fact that eggs or chicks were not observed. Again there were no temporal pattems to foraging distances (Figure 3.6b), but the home range area \À/as so small that this is not surprising. Unfortunately, despite considerable effort, this bird could not be recaptured prior to the failure of its radio-transmitter battery. KB8 KB8 was captured in May, prior to the breeding season, and was very mobile prior to mid- September when it established a breeding territory approximately two kilometres north of its previous roost sites (Figure 3.7). KB8 was actually recorded breeding in November, and it remained within the breeding territory until radio-tracking ended in January of the following yeat. These movements accounted for KB8's relatively large home range of 337 ha (Table 3.3), however, the actual area used during the breeding period was only -39 ha, which is similar to the home ranges of the other breeding birds The foraging distances for this bird were indicative of this pattern of movement, with numerous forays of between 600 m and 2300 m early in the tracking period, followed by much reduced foraging distances (i.e. generally less than 400 m) when the breeding tenitory was established (Figure 3.6a and b). Unfortunately it was not possible to determine post-breeding patterns of movement. Prior to breeding KB8 roosted in the south-west of its range (Figure 3.7) at a communal roost, with up to 15+ birds (including KB3, KB6, KBl1 and KB12). The number of roost areas used by this bird was relatively high (Table 3.4) due to its mobility prior to breeding. 59 KB4 - Kernel home nange estimate (90%) = 39 6t. O Diurnal(Roost)Sites a O Noctumal(Forage)Sites KB7 - Minimum convex polygon home range I a .t estimate (90%) = 346 ha. a O Diumal(Roost)Sites It O Nodumal(Forage)Sites KBB - Harmonic mean home nange estimate (90%)= 337 ha' O Diurnal(Roost)Sites O Noctumal(Fonage)Sites Landcover Ç I RemnantVegetation Regrcwth Vegetation Regmwth Vegetation - u/storey species only Clearcd Land I Planted Trees Swamp I Dams A oo lÂ\ N 0 2OO 400 600 800 Metres Figure 3.7 Radio-tracking fixes and home range boundaries for three bush stone-curlews Burhinus grøllarìus (K84, KB7 & IC8) at rKB l)owns', south-western Kangaroo Island, 1997 - 1999. NB. For these three birds the best home range estimates were producedby different analysis techniques (see Section 3.3.3). 60 KB9 KB9 was captured in June, just prior to the breeding season, and like KB8 was relatively mobile prior to breeding in October, although its home range size was much smaller at 120 ha (Table 3.3). Also all of KB9's foraging distances were less than 1200 m (Figure 3.6a). KB9 was recorded using ten roost areas (Table 3.4), which was also indicative of a relatively mobile bird. Prior to breeding KB9 was observed within the home range area of KB10 on several occasions (Figure 3.8), although the birds were not recorded in the same vicinity at the same time. A reduction in foraging distances is evident at the end of the tracking period for this bird (Figure 3.6b), which coincided with breeding. The nest site was located centrally within the home range area,in the vicinity of where the bird had roosted previously, although there was no prior indication that this site might be used for nesting. Unfortunately the radio- transmitter came off this bird shortly after eggs were detected. KB 1O KB10 was recorded using the smallest home range of any bird(26 ha; Table 3.3), and only occasionally moved outside of this area throughout the tracking period (Figure 3.8). It was captured prior to the breeding season (June), but was always flushed with another bird from the same general roost area. As such it was only recorded using three roost areas (Tabl e 3.4) and these were contiguous. Although tracking was completed in February, this bird was also observed within this home range area well after the breeding season in May, and then again in June and August, indicating that it was probably resident within its observed home raîge throughout the non-breeding season. Given the small area used, it was not surprising that most foraging distances were less than 200 m, and the longest recorded movement was less than 700 m (Figure 3.6a). A minor reduction in foraging distances was recorded after week 36 (Figure 3.6b), coinciding with when breeding occurred, although eggs were not located until October (they were probably overlooked earlier). Non-breeding birds KB5 KB5 was radio-tracked over avery long period,likeFC2, because it was recaptured and its transmitter was replaced. The home range size of KB5 was relatively large at367 ha (Table 3.3), although KB5 was sedentary within this well defined area and made consistent 61 { a o ( a Õ * rtÌ ì b KB9 - Kemel home nange estimate (90%)= 120ha. a it . O Diumal (Roost) Sites .,"* Noctumal(Forage)Sites lh Et O t , KB10 - Kemel home nange estimate (90%¡ = 26 ¡.. 1 * * O Diumal(Roost)Sites tr ù O Noctumal(Fonage)Sites t t Ò å a o t t Landcover RemnantVegetation J - : Regrcwth Vegetation I I a Regrowth Vegetation - u/storey species only Cleared Land il {|Ð t I Planted Trees {' ' ì Swamp I Dams A N 0 100 2OO 300 400 500 Metres Figure 3.8 Radio-tracHng fixes and home range boundaries for two bush stone-curlews rKB Burhìnus grallarius GCa & KB10) at Downsr, south-western Kangaroo Island, 1998 - L999. NB. One location obtained for KB9 is not shown. It was approimately 2lcnto the west of the main focal area of this bird's home range, and was obøined the day after the bird was captured. 62 movements. The foraging distances of this bird were relatively short, with few forays of over 1200m (Figure 3.10a). KB5 regularly used one major roost area that was located almost centrally within its home range (Figure 3.9), although a total of 19 roost areas were used (Table 3.4), and movements between these roost areas helped account for the large home range síze. There was no apparent trend in the foraging distance data, either spatially or temporally (Figure 3.10a and b). This observed pattern of movement resulted in the home range area being used relatively uniformly (Figure 3.9), like some of the breeding birds. However, this bird was rarely observed with other birds, and remained mobile throughout the breeding season, indicating that it was not a breeding bird. KB7 KB7 was radio-tracked in the period between breeding seasons (February to July) and was recorded using a large area of 346ha (Table 3.3). This bird always roosted in a patch of scrub along the westem boundary of 'KB Downs' (Figure 3.7), although it showed no real fidelity to a particular roost site, and was recorded using nine roost areas along this boundary (Figure 3.1 and Table 3.4). From here KB7 made a wide range of foraging forays to the north and to the south-east. V/hile some foraging occurred just to the north of the roost area (Figure 3.7) at distances of only 300 m to 600 m, the majority of foraging distances were between 1300 m and2400 m (Figure 3.10a), which accounted for the large home range size of this bird. There were no temporal pattems to foraging distances (Figure 3.10b). The wide-ranging movements of this bird were similar to three other birds that disappeared from the study area shortly after tracking began (K83, KB6 and KBl2; see section 3.3.6), and this bird was also lost just prior to the breeding season. Based on the movements of these birds KB7 presumably dispersed. Despite extensive searches from the surrounding road network it was not relocated. KBl 1 KBI I was radio-tracked during the breeding season and had the largest home range recorded at 877 ha (Table 3.3) and ranged over the whole study area at'KB Downs' (Figure 3.9). Throughout the tracking period KBl l showed short-term fidelity to roost sites, but regularly moved to new roosts, using a total of 15 different areas (Table 3.4). However, the large home range size did not result from a gradual shift between roost areas, as foraging distances of up to, and greaterthan,2500 m,'wererecordedforthisbird(Figure 3.10a). KBll regularly 63 KBS - Kemel home range estimate (90%) = 367 ha. O Diumal(Roost)Sites O Noctumal(Fonage)Sites a KB11 - Kemel home range estimate (90%) = 877 ha. { O Diumal(Roost)Sites a O Noctumal(Fonage)Sites o a t i a a{ O a a Landcover o l¡ RemnantVegetation È a I Jl a o o.l" oo. O . . Regrowth Vegetation o a o a .cb I . o I Regrowth Vegetation - u/storey species only t .O + :> \ o I Cleared Land Ð o oo -$ Planted Trees à J} I 4 I t SwamP 1 <É , : tr 1r a I Dams ' a I a I o o t 4 o o a þ O .O * cÕ a O o o o a a o¡)a + A N a, a o 0 200 400 600 800 1000 Metres a o , a a o I a o t I 4 t o Figure 3.9 Radio-tracking fixes and home range boundaries for two bush stone-curlews Burhinus grailørtus (I(Bs & KBll) at rKB Downst, south-western Kangaroo Island, 1997 - 1998. 64 Figure 3.10a. Frequency of 'foraging distances' for four non-breeding bush stone-curlews Burhinus grøllarius on south-western Kangaroo Island between 1996 and 1999. 'Foraging distances' are the distance between diurnal locations and noctumal locations. 'Foraging distances' were only measured when diurnal and nocturnal fixes were obtained sequentialty (i.e. on the same day), except where birds used the same roost every day, in which case foraging distances for all noctumal fixes could be determined. 6 FC3 ¡ KB5 ¡ KB7 ¡ KB11 18 16 14 12 o o 10 = oE I l¡. 6 4 2 0 sNCO:ttO(gt-@O) o N cr)sto(oN @ o, O N CO s rr) rf) rr-lillll¡ rrr N N N N N N C\¡ tl I ¡rll I I I I I o (o t- @ o) O N CO o)o NcD.trr) N N N N Ns Foraging Distances (x 100 m) , 65 Figure 3.10b Temporal patterns in 'foraging distances' for four non-breeding bush stone-curlews Burhinas grallarius on south-western Kangaroo Island between 1996 and 1999. Foraging distances (see Figure 3.7a&b) are plotted against the week of the year when they were recorded. Week I is the first week in January. KB5 was radio-tracked for 16 months and data for the same weeks in consecutive years is combined. Note scales on the y-axis (foraging distances) are not the same for each bird. 2400 1 000 (a) FC3 e (c) KB7 o o 0 2000 800 o g o F O9 o gs 1 600 g o o 600 oe o r oo o 1200 o8 -o^8 oê a 400 o g ooo 800 o ¡ 200 400 o n I o g o 0 0 D ¡ 5200 s 1 800 (b) (d) KB11 KBs 4800 o t 1600 4400 a o '1400 o o 4000 3600 n 1200 o 3200 c 8 9oo o 1 000 o Vo^ 2800 e .8 OO 2400 800 o s e8 oB" o o 2000 a I 600 o I o g 1600 o I (m) E8 oo O9 o 400 g o8 U B 1200 O9 Oo g B. 800 E g. o 8 0 æ0 0 400 o 0 o o ð BË 0 0 o 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 0 4 I 12 16 20 24 28 32 36 40 44 48 52 Weeks of the Year Weeks of the Year 66 traversed much of its large home range on single nights, and on many occasions was subsequently observed returning to the same roost area. Again, there were no apparent temporal patterns to the foraging distances (Figure 3.10b). These wide ranging movements were consistent with KB7, and the three other birds that were lost from this study site (K83, KB6 and l{I3I2 see section 3.3.6). KB11 was also recorded at the communal roost site along with KB8 and these other three birds. It was eventually lost, and presumably dispersed. Again, despite extensive searches from the surrounding road network it was not relocated. FC3 FC3 was a first year juvenile and was captured in December. This bird spent the whole radio- tracking period within the home range of its parents (FC2; see Figure 3.5), and had a home range size of only 32 ha. It was usually recorded foraging close to FC2 and therefore the pattern of its foraging distances were very similar to that bird (Figure 3.10a). FC3 also roosted with FC2 or nearby, (Figure 3.5) and therefore was recorded using the same small number of roost areas (only 4; Table 3.4). Not surprisingly no temporal pattem to foraging distances was observed (Figure 3.10b). Unfortunately FC3 was lost at the time when attempts were made to replace its transmitter, and therefore it was not possible to determine if this bird dispersed from its natal range, or if the transmitter battery went flat. FC3's parent, FC2, was recorded breeding shortly after this period, so FC3 may have been encouruged to disperse. 3.3.6 The movements of the five birds for which home range estimates could not be determined As indicated above, estimates of home range sizes for five birds were not calculated because of the short duration of radio-tracking periods and the subsequently small number of fixes obtained, however, these birds provided useful data that contribute to the understanding of movements by the birds (Figure 3.11). This information is outlined below for each bird' KB1 KBI was one of the first birds to be radio-tagged, and little night-tracking occurred during this early stage of the project, and as a result few foraging fixes were obtained. The movements of KBI were indicative of a non-breeding bird, although the lack of data makes this uncertain as tracking began in the breeding season, and breeding attempts may have been 67 o KB1 o KBz @ KB3 o KB6 o KB1 2 Landæver I RemnantVegetation ,*-=, RegrowthVegetation Regrowth Vegetation - u/storey species only Clearcd Land I Planted Trees :".*ii! Swamp I Dams A N 0 2OO 400 600 800 Metres Figure 3.11 Radio-tracHng fixes for five bush stone- curlews Burhinus grallaríus (K81, KB2, KB3, KB6 & KB12) at rKB Downsr, south- western Kangaroo Island, 1996 - 1998. 68 overlooked. Unfortunately this bird subsequently died, apparently from natural causes. This followed a long dry summer and very late break in the winter season that was exceptionally cold and wet. On one of the last nights I tracked this bird hail storms occurred all night. This sudden and extreme break in the season may have contributed to the death of this bird. I<82 KB2 was also one of the first birds to be tagged and few foraging fixes were obtained. However, KB2 was captured at a site where a pair of birds were regularly observed with chicks, and was thought to be one of these breeding birds. This was supported by the presence of another bird that responded to alarm calls made at the time of capture. The pattern of fixes for KB2 was also consistent with a breeding bird with the same general atea used for roosting, and foraging recorded nearby. Unfortunately this bird also died, apparently from predation, although the metal leg band had pierced the skin of this bird, and this undoubtedly contributed to its death. Larger metal bands, that had their edges filed, were subsequently used on all birds caught. KB3 KB3 was tracked for only two weeks after capture before it disappeared. During this period it was recorded using the communal roost (as mentioned above) and ranged to the limit of the study area at 'KB Dotvns'. However, after extensive searches from the surrounding road network this bird was eventually relocated eight kilometres away from its last known location on 'KB Downs'. This information was obtained just prior to the breeding season. KB6 KB6 also showed similar movements to KB3 within the study area, prior to being lost after less than three months of radio-tracking. This bird was also recorded using the communal roost, although it also used several other roost sites. Although inconclusive, the movements of KB6 also suggested that it dispersed from the study area, assuming transmitter failure did not occur. Extensive searches from the surrounding road network failed to relocate KB6. This bird was tracked between August and October 1997, in the breeding season, and was therefore considered a non-breeding bird. 69 KB 12 KB12 also showed similar movements to KB3 within the study area, prior to being lost after less than three months of radio-tracking just before the breeding season (June to August). This bird was also recorded using the communal roost, and ranged widely over 'KB Downs', with these movements suggesting that KB12 also dispersed from the study area, assuming transmitter failure did not occur. The timing of radio-tracking makes it possible that this bird subsequently went on to breed. Again, extensive searches from the surrounding road network failed to relocate this bird. 3.3.7 Summary of patterns of home range size and home range use by the birds From the information above three groups of birds with different patterns of home range size and use are evident. These groups are: 1) resident breeding birds; 2) mobile breeding and non-breeding; and 3) resident first year juveniles. A brief summary of home range sizes and pattems of movement for each group is outlined below. 1) Resident breeding birds (see FC1. FC2, KBl, KB2, KB4 and KB10) Four of the six breeding bush stone-curlews were clearly resident within relatively small home ranges (26-64 ha; see Table 3.3) throughout the radio-tracking period, and observations indicated that these birds occupied these home ranges all year round. When flushed these birds were nearly always observed with another bird, confirming that they were paired, and they also showed a high fidelity to a relatively small number of roost areas (see Table 3.4). Not surprisingly the foraging distances recorded for these birds were relatively short (Figure 3.6a), which simply reflected the small area used by these birds. These birds were rarely recorded making exploratory trips beyond their home range areas. KB6. KB7, KBl l and KB 12) All of these birds are grouped together because they showed similar patterns of wide-ranging movements that resulted in larger, relatively loosely defined, home ranges compared to the birds in group 1. As a result home ranges were typically an order of magnitude larger than the home ranges of the resident breeding birds. Five birds in this group were recorded using a communal roost during the non-breeding season (K83, KB6, KB8, KBl1 and KB12) and were therefore associated with a loose flock of birds duringthat period. One of these birds 10 was subsequently recorded breeding (KB8), although another (KBll) did not breed in the following breeding season. The other three birds recorded at the communal roost (K83, KB6, and KB 12) were all subsequently lost early in the following breeding season. KB3 was relocated eight kilometres away, suggesting that all three birds probably dispersed. Unfortunately budget constraints prevented aerial tracking from occurring to record the patterns of dispersal. It is likely that some of these birds subsequently established breeding territories (like KB8), while others continued to roam widely without settling to breed (like KB11). All of the birds that were lost ranged over wide areas and showed no patterns with regards to where they foraged. Their movements within and between, nights were erratic, which made radio-tracking relatively diff,rcult. The foraging distances from roosts for these birds were typically over two kilometres, and in some cases much longer (Figure 3'7a). The data indicated that the large home range sizes recorded for these birds resulted from the long foraging distances, rather than a gradual shift of a smaller home range across the landscape. The two breeding birds (KB8 and KB9) showed a distinctly different pattern of movement compared to the resident breeding birds, which resulted in relatively latge home range sizes (337 and 120 ha; see Table 3.3). During the pre-breeding season these birds were relatively mobile and foraging distances were typically long, particularly for KB8 (see Figure 3.6a)' Use of roost sites was also indicative of mobile birds, especially for KB8, which was recorded using the communal roost as indicated. However, when breeding commenced KB8 occupied a relatively small area, similar in size to the home ranges of the resident breeding birds. As indicated the radio-transmitter fell off KB9 just after breeding was recorded' One bird within this group did show some fidelity to a large home range area (KB5), and this bird was also not recorded either with any flocks of birds, or breeding. Holever, despite being relatively less mobile, the home range area, and lack of breeding attempts clearly places this bird in this group. Another bird (KB7) showed very similar patterns of movement to KB3, KB6 and K812. This bird was also lost and is thought to have dispersed, although it was never recorded at a communal roost. 3) First )¡ear juveniles (FC3) These birds were deliberately not targeted during this study. However, one first year juvenile was captured along with one of its parents. This bird remained within the home lange area of its parents until at least the following breeding season. 7l 3.4 DISCUSSION The impact of attaching radio-transmitters to the birds The hamess system that was devised, after some minor trial and elror, proved to be effective, in that only one transmitter was known to have fallen off a bird, and more importantly, all birds that were recaptured showed no outward signs of injury or distress from carrying the transmttters Estimating movements using radio-transmitters assumes that the natural behaviour of the birds, (including reproductive success, movements, survival and home range sizes), are not affected by the transmitter. This has been the subject of numerous studies (egBntger et al. 'Wanless 1991, Foster et al. 1992,Massey et al. 1988, et al. 1988 and Ptetz et al. 1993, Garrettson et al.2000), particularly in America. Garrettson et al. (2000) compared the behaviour of captive ducks with back-pack transmitters and implanted transmitters with control birds and found that birds with back-packs exhibited altered behaviour, by spending more time on comfort movements and less time in the water, Pietz et al. (1993) found similar results with mallards. The other studies were less conclusive in their results, finding that it was difhcult to eliminate the impact of other factors. The assessment of impacts of radio- transmitters ideally requires prior knowledge of the behaviour of the birds, or the study of control animals to gain that knowledge (i.e. as in Garrettson et al. 2000). However, this would be very difficult, if not impossible, with wild birds. Given the limited knowledge of bush stone-curlew behaviour I was not able to specifically determine any adverse impact of the transmitters. Based on my observations of the birds' behaviour the impact appeared minimal. Six of the birds were recorded breeding, and this combined with known movements between roost areas and forage areas (often up to several kilometres) suggests that these birds were not affected by the transmitters. Impacts may have been more subtle, although the patterns observed in the data also suggest that the birds were behaving 'naturally'. On only one occasion \Mas a transmitter displaced by the bird (the elastic straps had not severed), and on another occasion one bird became slightly entangled, possibly because the hamess was too loose to begin with, and the elastic may have also stretched. Fortunately these problems were easily overcome by regularly checking the birds and visually observing their behaviour (i.e. checking that they were running and flying well). 72 Unfortunately the first three birds that were radio-tagged all died between 6-8 months after capture. The cause of death for all birds was unknown although the transmitters did not appear to have been the cause. Two of the birds were recorded dead at the same time, and this coincided with a harsh break in the season following a long dry summer, which possibly contributed to their deaths. The technique for the attachment of transmitters did not vary between birds, so it is difficult to determine if the transmitters affected the survival of these birds. The birds were thought to have died of natural causes, including predation, which was observed during the course of the study for at least two other (non-tagged) birds' Different tlpes of elastic, of the same width, did have different qualities in terms of their elasticity and the ability to retain original elasticity. Ideally the elastic should retain as much of its original elasticity as possible to ensure that the transmitter remains firmly attached. Given the lack of similar studies, I originally intended to focus this study on breeding birds to determine the spatial arïangement of their home ranges, as well as home range sizes. However, when catching birds, the luxury of making choices based on age and breeding status of the birds was not possible. Instead efforts were made to only attach transmitters to adults, which increased the chances of catching a breeding bird. Therefore the only major distinction that was made between the birds studied was whether or not they were breeding. The factors identifying adults, primarily moult and weight, were effective for all but the early stages of the breeding season when the previous year's young were similar to the adults. For all but eggs one bird, breeding status was determined simply by observing breeding attempts (usually were detected) after noticeable changes in the extent of movements of the birds. This information is important for interpreting the data collected. One limitation of the study was that the birds were unable to be easily sexed. The sex of the study animals was potentially an important determinant of their movements and behaviour. Hoyever, this limitation was partially offset by the fact that when breeding birds were observed they were always with another bird, presumably their partners. This was the case for all of the breeding birds, and was also observed outside the breeding season. This suggests that the sex of the breeding bird would not have a major impact on its movements. This is supported by the fact that both sexes incubate and brood the young (Johnson and 73 Baker-Gabb lg94). Johnson and Baker-Gabb (1994) also found that outside the breeding season some birds remained as resident pairs, in which case movements were also likely to be similar between sexes. The sex of the birds may have a greater bearing on the movements of the non-breeding birds, particularly with their larger movements and the dispersal of some of these birds. Finally, itwas also intendedto focus on small study areas to consider overlap of home ranges but this was difficult because some birds, including breeding birds, moved over relatively large areas, and were not necessarily captured near the core of their home range. Despite these difficulties consistent pattems emerged from the 15 birds that were eventually captured and radio-tracked, and these provide a good understanding of the home range sizes and movements of these birds. The radio-triangulation technique was considered an effective, efficient and accurate means of determining the locations of bush stone-curlews. The use of a vehicle at 'KB Downs' to travel between the birds was the only feasible technique available given the large distances moved within a níght, and between nights, by some birds. I became very familiar with the layout of the study areas and was able to select points from which to obtain bearings that were easily recognisable on the enlarged aerialphotographs. This allowed me to quickly determine successive locations that ensured an angle of as close to 90o as possible between the bearings. This helped to ensure the accuracy of the data, and as indicated in the methods, bearings that met at angles that were too obtuse (>120") or oblique (<60") were discarded. The time between recording two successive bearings for the same bird varied depending on the distance to the bird, the nature of the terrain, and layout of fences and gates. The minimum and maximum time was approximately two and five minutes respectively (pers. obs.). During this period the birds may have moved short distances, but this was not considered a major problem. My understanding of the study area, and the strength of the signal from the first bearing, provided me with an approximate idea of the location of the bird. Therefore any longer movements that occurred whilst I was shifting to obtain the second bearing were readily detected. New bearings were obtained when this occurred. 74 Finally two other factors helped to off-set the impact of the error involved with the triangulation technique. First, those birds that were resident (eg FCl, FC2 and FC3, KB4, KB9 and KBl0) could often be located from the same points night after night. The advantage of this was that these points were selected to ensure that the angle between the bearings was close to 90o and that they were relatively close to the birds to ensure a strong signal. Therefore for those birds with small home ranges, potential error was much reduced. Second, on numerous occasions the birds were visually located to check their condition, or to collect faeces from their roost areas (see Chapter 5). In both situations the birds usually moved once they were aware of my presence. However, they were always observed within 20m of the fixes obtained from triangulation. In the case of collecting faeces, I was often able to walk directly to roost areas based on the triangulation data, regardless of whether or not the birds were observed. In the context of the home range sizes, elTors of this magnitude were considered a minor problem. 3.4.1 Home range sizes and patterns of movements of the birds The general pattems of movement and home ratTge estimates that I recorded in this study, and the three groups of birds that I subsequently identifred, were broadly similar to those summarised in Marchant and Higgins (1993). In particular the observation that during the non-breeding season some birds remained as resident pairs (eg, FC2, KB4 & KB10) while others form small flocks of 5-10 individuals (e.g. KB3, KB6, KB8, KBl l 8. I3I2) was consistent with previous observations of the birds (see Marchant and Higgins 1993, Johnson and Baker-Gabb 1994). KB8 also demonstrated that some birds observed within the loose flocks during the non-breeding season subsequently established breeding territories, whilst others roamed more widely across the landscape and probably dispersed to new areas (eg , KB3, KB6, KB11 and KB12). Prior to this study these patterns of movement had only been inferred from anecdotal observations or observations of birds within their daytime roosts (eg 'Wilson Johnson and Baker-Gabb 1994, 1989). This is the first study that has quantified such pattems of movement with the use of radio-tracking. The home range sizes and patterns of movements for the three groups of birds outlined in the results are discussed below in more detail. 75 Group (1): Resident breeding birds Four resident breeding birds occupied surprisingly small home range areas of between 26 and 64 ha. The estimated size of home ranges of breeding birds in northem Victoria in the past ,was approximately 70ha (based on four breeding pairs per 290ha property; see Johnson and Baker-Gabb 1994), which is similar to the larger home ranges recorded for resident breeding 'Wilson birds in this study. (1939) concluded that a pair of bush stone-curlews within residential Brisbane probably ranged over an area of 95 hectares, although this was probably reduced to 4I hectares in the breeding season. Although the habitats are not comparable, this estimate of home runge size is also very similar to this study. Other diumal observations in northem Victoria indicated that one pair of birds used five favoured timbered areas for roosting within 12 hectares, and another pair roosted within a one hectare atea all year round (Johnson and Baker-Gabb 1994). The breeding birds in my study showed comparable patterns of use of roost areas, with three of the breeding birds using areas of less than five hectares, often within the same patch of vegetation, throughout the period that they were radio-tracked. Johnson and Baker-Gabb (1994) noted that some resident pairs used the same favoured site for roosting for weeks, or even months, if they were not disturbed, and some birds probably used the same site all year round. Other birds were observed using three to four sites within a small area. My data showed that some birds did use the same sites all year round, and in several instances breeding occurred within short distances of these sites (e.g. FC2,KB4 and KBl0). The use of such small areas for breeding would suggest that these areas are of optimal quality, However, based on casual field observations it was not clear what specific factors influenced habitat quality, with apparently unused sites appearing suitable. There may be important intrinsic factors that effect the relative quality of areas for bush stone-curlews. Regardless, adequate cover for roosting, and in some cases nesting, along with adjacent open areas for foraging are clearly fundamental requirements of these birds. Remnants that provide access to suitable foraging habitat on all edges may have a higher value. Also a variety of substrates within the foraging habitat may improve the quality of a site. For example, the breeding bird with the smallest home range (K810) roosted in a small remnant of vegetation that was a' situated on a calcarenite ridge. The vegetation on this ridge was quite open at ground level as there was no understorey, but numerous mallee stems and a dense canopy of low mallee provided good cover. The remnant was surrounded by cleared land with several isolated trees, with parts of the calcarenite ridge, and adjacent lateritic soils exposed, providing 76 heterogeneity within the potential foraging substrate. The open nature of the vegetation in the roost area may have also made it suitable for foraging. As indicated it is not clear if any of these factors influence the quality of a site for bush stone-curlews. Regardless of what factors combine to create optimal habitat, obviously relatively small areas are able to provide adequate resources for raising young, and on western Kangaroo Island these areas appear to be widespread across the landscape based on the number of birds observed, including chicks and juveniles (pers. obs). Remaining within such small areas has the obvious benefit of familiarity with these sites. This is likely to have advantages with regards to having knowledge of 'hotspots' for food resources, and predator avoidance. All of these factors may influence breeding success, which in itself may influence longer-term fidelity to sites, with birds establishing permanent home ranges where they are able to breed successfully. The spatial arrangement of the home ranges of resident breeding birds was not specifically determined due to difficulties in identifying and catching birds that occupied adjacent home ranges. However, observations suggested that breeding birds used exclusive home ranges, and that these were probably not contiguous in most cases. Also, during the 1998 breeding season I observed six different breeding attempts by six pairs (including KB9 and KB10) within an aÍea of only approximately 200 ha. It is quite possible that other pairs were not discovered. The density of breeding pairs in this area was therefore high, and potentially all suitable habitat was occupied. The spatial arrangement of habitat (i.e. cleared versus vegetated land) is one simple factor that is likely to influence the density of breeding pairs, as all birds require vegetation to roost in and open/cleared areas for foraging (pers. obs.; see Chapter 4). A patchy landscape with numerous vegetation remnants of varying sizes is therefore likely to favour bush stone-curlews, and probably accounts for this apparently high density of breeding pairs at this site on western Kangaroo Island. In contrast much lower densities of birds were observed on the eastem end of Kangaroo Island (pers. obs) where relatively fewer, and smaller remnants are available. The intensity and type of land-use may also play an important role in determining the sites chosen, and the overall home range sizes of resident breeding birds. In particular, changes to the abundance of food resources resulting from agricultural practices such as cropping may make some areas less suitable, resulting in larger home ranges. A comparison with the sizes and spatial affangement of home ranges on the eastern end of Kangaroo Island would help to determine what factors influence the 77 suitability of sites for these resident birds. This was attempted but difficulties with locating and catching birds on eastern Kangaroo Island, and time constraints, prevented this from occufflng. Groups (2): Mobile breeding and non-breeding birds As indicated, breeding and non-breeding birds were combined in this group because of their similar home range sizes and patterns of movements. All of these bird had home ranges that rwere a magnitude of order larger than the home ranges of the resident breeding birds. These range sizes are comparable with the estimates suggested by Johnson and Baker-Gabb (1994) for bush stone-curlews in northern Victoria' Five of the eight birds within this group joined a loose flock of birds during the non-breeding season, and were observed with up to 15+ birds at a single communal roost on several 'While occasions. only one of these birds was subsequently recorded breeding, several others were lost early in the breeding season and may have dispersed to breed elsewhere' This behaviour is consistent with observations of the species elsewhere (Johnson and Baker-Gabb lgg4). Unfortunately the demographics of this flock were not known, as the age and maturity of these birds probably provides the key to the observed patterns of movement. However, as the resident breeding (group 1) birds appear to form the core of the breeding population, it is reasonable to speculate that the birds that formed loose flocks, and were relatively mobile, were younger, immature birds. The time to sexual maturity in bush stone-curlews is not known, but for these relatively long-lived birds (Marchant and Higgins 1994) may be greater than one year. This would also in part account for the existence of such flocks' Clearly a proportion of these birds breed after the flocks disperse, with one bird recorded doing so in this study. In contrast other birds did not 'settle' within discrete home ranges and remained mobile throughout the breeding season, and while radio-tracking occurred. The assumption that resident breeding pairs occupy the optimal habitat also helps to account for the formation of these loose flocks, as opportunities for younger birds to establish suitable home ranges for breedin g may be limited if all prime breeding habitat is occupied. Although only speculation, a combination of less than optimal habitat and inexperience is likely to result in failed breeding attempts by these birds. As a result these birds are probably more likely to continue to join loose flocks during the non-breeding season until a better location and/or breeding success can be attained. If this is the case, there would be no advantage in 78 remaining resident within sub-optimal habitat, and the chances of finding a 'vacancy' in optimal habitat are increased considerably by ranging widely across the landscape. The dynamics of establishing pair bonds are also unknown, and the loose flocks may play an important role in this process. The patterns of foraging distances for all of the mobile (group 2) bush stone-curlews indicated that they were not gradually shifting their home range as movements were without any obvious pattem, and the birds often retumed to previously used areas (pers. obs.). These birds were basically ranging over much larger areas than the other birds, and this was reflected in the fact that their foraging distances (see Figure 3.9) were typically much longer than the other birds. In addition, although the radio-transmitters on the birds that were lost (i.e. KB3, KB6, KB7, KB11 and KB12) may have failed, one of these birds (KB3) was re-located eight kilometres away, confirming that some birds were dispersing. As indicated above, based on these observations I believe that KB6, KB7, KB11 and KB12 also dispersed. The use of communal roost sites has been recorded in the past (Marchant and Higgins 1993), and in some cases much larger flocks have been recorded (e.g. Campbell and Barnard l9l7). However, given the decline of this bird in southern Australia flocks like these are rarely observed today (Marchant and Higgins 1993). The presence of such flocks on Kangaroo Island is therefore significant. The apparently high densities of breeding pairs, and subsequently high levels of recruitment, at least on the western end of Kangaroo Island (pers. obs.) probably accounts for the presence of such flocks. The availability of large areas of undisturbed vegetation may also be important because known sites used as communal roosts are remote from disturbances. Given that densities of resident breeding pairs appeared to be quite high at 'KB Downs' (i.e. suitable breeding habitat is occupied), the presence of relatively large flocks of probably younger birds would signify that the population is healtþ, and that recruitment rates are higher than rates of loss of mature breeding birds. This further supports the conclusions in Chapter 2 that Kangaroo Island provides the only secure stronghold for this species in southem Australia. Although the demographics and dynamics of these mobile bush stone-curlews require further investigation, the presence of such flocks is clearly an important indicator of the health of the population. One bird in this group has not yet been mentioned (KB5), primarily because it was not observed with a loose flock and did not breed, however, this bird did range over a wide area 79 and showed the same patterns of movement as the other birds in the group, albeit within a relatively well-defined home range. Group (3): First )¡ear birds First year birds were abundant at the study sites þers. obs.) and many were caught and banded. With one exception these birds were specifically not targeted in this study because their movements were expected to occur within the home ranges of their parents. This was confirmed from the radio-tracking of one juvenile at FCHQ. This bird remained within the home range of its parents (see FC2) for the whole period of tracking (9 months; Table 3.3) and was always located near FCZ, which was tracked at the same time. Johnson and Baker- Gabb (1994) observed young with their parents from three to nine months after hatching, although accounts in Marchant and Higgins (1993) indicate that fledglings are usually chased off by the adults when second breeding attempts are made. Unfortunately FC3 was lost just prior to the expected failure of its radio-transmitter, although based on the above observations it appears likely that this bird dispersed. FC2 was observed to be incubating eggs again in October, approximately one month after FC3 was lost. 3.4.1 Summary and conclusions As discussed, the factors that determine the suitability of sites for breeding, and result in pairs remaining resident within small home ranges are not clear. The spatial anangement of habitat features, and in particular remnant vegetation versus cleared land may play an important role, as may food resources. However, another factor that may be equally important is simply social organisation, and particularly interaction with conspecifics. At both of my study sites a cacophony of bush stone-curlew calls usually erupted just after dusk, and at times continued intermittently throughout the night. Numerous birds, and particularly pairs of birds, responded to each other across the landscape, as if to reinforce their claim to their 'patch'. Such a vocal presence, and probable claim to a home range, may present a rather daunting scenario for young bush stone-curlews trying to establish themselves as successful breeding pairs. Conversely, these vocalisations are also likely to assist young birds with seeking partners andlor'vacant'home ranges. Whilst the purpose of these vocalisations is difficult to quantify there is no doubt that they play an important role in bush stone-curlew social organisation. The spatial arrangement of areas used by the breeding pairs may in part be organised through these vocalisations, particularly as direct observations ofeach other are not 80 possible at night. The calls therefore also allow birds to locate each other. Given the apparent importance of vocalisations, for whatever reason, it is not clear what effect this may have for bush stone-curlews that occur in isolated pockets on the mainland, with few conspecifics nearby. If nothing else, dispersal of young (if recruitment occurs) is likely to be hampered in these fragmented areas. Clearly a proportion of the population of bush stone-curlews on western Kangaroo Island is not resident and roam over relatively large home ranges. The large sizes of these home ranges resulted from wide-ranging movements, with birds typically returning to previously used roost areas, such as the communal roost. Given the small areas that can support breeding pairs, these movements are indicative of exploratory trips that are made for social reasons (i.e. to find a mate and./or suitable habitat for breeding), rather than being necessary to satisfy feeding requirements. This supports the notion that social interactions, and vocalisations, play an important role in the spatial use of habitat by bush stone-curlews. Clearly, these birds would not have to make such wide-ranging movements if suitable breeding sites were not limited. As indicated, observations suggest that such sites are limited because they are already occupied by breeding pairs, rather than the habitat being unsuitable. This supports the assumption that the population of bush stone-curlews is healthy, at least on westem Kangaroo Island, which based on all observations appears to be a 'source' for the population. Johnson and Baker-Gabb (1994) suggested that outside the breeding season bush stone- curlews moved within a loosely defined home range, which was probably determined by the availability and spatial affangement of suitable roosting and nesting areas. A diurnal range of up to 250 hectares was suggested based on this observation, however, the nocturnal range was considered much larger. This estimate is comparable with the estimates for the mobile birds in this study, although it is much larger than for the resident breeding pairs on western Kangaroo Island. It is quite possible that the birds show a different pattem of resource use where suitable areas of roosting habitat are much less abundant, such as in northern Victoria' The extent of remnant vegetation within my study sites (see Figures 3.5 and 3.11) is typical of western Kangaroo Island, where much of the remaining 50%o of natural vegetation remaining on Kangaroo Island occurs (Ball and Camrthers 1998). In comparison, habitat clearance and fragmentation is relatively higher on the eastern end of the Island, although remnant vegetation is still relatively abundant compared to the mainland, and some large areas of vegetation remain, particularly along the south coast of the island. Overall approximately 81 50% of the remaining vegetation on Kangaroo Island occurs on private land (i.e. -25% of the area of the island). In contrast in northern Victoria less than five percent of private land is covered with native vegetation (Johnson and Baker-Gabb 1994). As a result the birds on Kangaroo Island potentially have more available diurnal habitat within a given area and this could account for smaller home ranges. Conversely, distances between suitable remnants in Victoria are likely to be much greater than on Kangaroo Island, and this could account for the suggested larger home ranges of birds there. ') 82 CHAPTER 4 CHARACTERISTICS OF ROOST, NEST AND FORAGING SITES SELtr]C'I'ED BY BUSH STONE.CURLEWS BURHINUS GRALLARIUS ON KANGAROO ISLAND. 4.0 INTRODUCTION Bush stone-curlews were once widespread and abundant across the mainland of South Australia but they are now classified as endangered following a major contraction of their range and population decline (see Chapter I and 2). Forlunately these birds are relatively common on several offshore islands, and Kangaroo Island, in particular, provides a sanctuary for a large number of these birds. The large size of Kangaroo Island and the absence of foxes make it the last secure stronghold for the species in southem Australia. prior to the settlement of southem Australia temperate woodlands were thought to have been the preferred habitat of bush stone-curlews. Today the birds still occupy areas of open forest and woodland, but partly cleared agricultural land with woodland remnants has also become important habitat for them (Marchant and Higgins 1993; this study). Unfortunately these temperate woodlands have become the most threatened ecosystem in Australia. Over 85% of the woodland that once covered a large area of eastem and south-western Australia has been 'Woodlands cleared, and replaced by wheat and sheep production (Robinson and Traill 1996)' growing on relatively fertile soils were cleared disproportionately and much of the remaining habitat occurs on rocky slopes and hills (eg. Paton et a\.2000). This situation exacerbates the problem for woodland dependent fauna, as the remaining habitat is of relatively poor quality. One of the highest concentrations of threatened birds in Australia occur within this habitat with twenty-five species of birds listed as extinct or threatened. Bush stone-curlews are one woodland dependent species that has become threatened in all four States where temperate woodlands were once widespread. In general, ground-nesting and ground-feeding birds are particularly prone to decline and local extinctions (Garnett Igg2), making bush stone-curlews one of the most vulnerable species. Few detailed studies of the ecology, and in particular habitat preferences, of this species have been undertaken. 83 As indicated, in contrast to the mainland an apparently healtþ population of bush stone- curlews exists on Kangaroo Island (see Chapter 2; Joseph 1981, Baxter 1995), where vegetation clearance has been less severe, and has occurred much more recently. Despite this, the agricultural areas are similar to those on the mainland in that the remaining native vegetation is fragmented, and typically occurs as small remnants or strips. Fortunately many remnants occur along creeklines, fencelines and roads and are therefore not necessarily of poor quality. This study sought to answer the following questions: 1. What are the characteristics of roost, nest and foraging sites chosen by bush stone- curlews on Kangaroo Island and are they different from randomly selected sites? 2. Is the habitat selected by these birds limited or threatened in any way? 3. What are the implications for management of the habitat used by bush stone-curlews? 4.1 Background information on habitat use by bush stone-curlews prior to settlement, bush stone-curlews are thought to have predominantly occurred in lowland grassy woodland and open forest in southern Australia, although as indicated above, much of this has now been cleared for agriculture (Robinson and Traill 1996, Johnson and Baker-Gabb l9g4). Today bush stone-curlews typically occupy lightly timbered areas of woodland or forest, including farmland with remnant patches of native vegetation. They no appear to prefer areas where the ground cover consists of short sparse grass and few or shrubs, and where the ground is covered with leaf litter and other fallen debris such as dead tree branches (Marchant and Higgins 1993). In inland Australia bush stone-curlews are generally found around ranges, lakes and watercourses with permanent water (Marchant and Higgins 1993). Bush stone-curlews roost on the ground, often amongst clumps of shrubs or trees, in patches of native vegetation or plantations. These patches can be small isolated remnants and roadside vegetation (Marchant and Higgins 1993). In northern Victoria the birds were found to roost in areas where percentage cover of debris fallen from trees is higher' There was also more bare ground, lower grass and less disturbance from farming than in surrounding areas (Johnson and Baker-Gabb 1994)' Nesting occurs on the ground and no nest of any description is constructed. Nesting typically occurs within open woodland vegetation where grasses are short and sparse. In these 84 situations nests are often placed near fallen timber (Marchant and Higgins 1993). Johnson and Baker-Gabb (1994) found nests to be on average 12.7 metres from the nearest tree, which is also consistent with the selection of open woodland areas. Nests are also occasionally placed in short grass or in faliow or recently ploughed paddocks (Johnson and Baker-Gabb ree4). Bush stone-curlews are known to forage on open ground, sometimes under trees, among grass, pasture or crops, irrigation paddocks, and in summer, around watercourses, dams and sv/amps (Marchant and Higgins 1993). Due to the difÏrculties of observing these birds at night no detailed studies of foraging habitat, or foraging habit, have been undertaken. Few detailed studies on habitat preferences of bush stone-curlews have been undertaken (eg Johnson and Baker-Gabb 1994) and all have occurred in a highly modified environment where native vegetation only occurs in small isolated remnants. As such the results of these studies will in part reflect the habitat that is available now, and not necessarily the preferred habitat of these birds. 4.2 METHODS 4.2.1 Locating sites used by the birds Between late 1995 and early 1999, sites used by bush stone-curlews on Kangaroo Island were located as part of a broader study of distribution, home ranges, movements and diet (see Chapters 2, 3 and 5). Three types of sites associated with three major activities were identified - foraging (nocturnal) sites, nest sites and roost sites. Radio-tracking helped to identify/locate all three types of sites, although this technique usually only provided an approximate location as triangulation was often used to obtain fixes. In particular, foraging sites could only be inferred from these triangulated locations and could not be precisely located on the ground because of difficulties with observing the birds at night. However, unlike nest and roost sites, the precise location of foraging sites was considered less important because the birds were relatively mobile whilst foraging anyrvay (see Chapter 3). Brief searches ìvere generally required to precisely locate nest and roost sites used by radio-tagged birds. This was necessary because of the wariness of the birds, which usually resulted in them being observed after they had already moved from the site they were using. The presence of eggs was used to confirm the location of nest sites and roost sites could be identified by an accumulation of faeces andlor feathers. 85 Intensive searching was also undertaken in conjunction with radio-tracking to locate nest sites, and in the process some roost sites were located. Photographs of all nest sites were taken to precisely relocate nest sites once the eggs were no longer present to minimise disturbance to the birds. Most sites were located within the major study arcas at Flinders Chase Park Headquarters (FCHQ) and 'KB Downs' but data were also collected at several other locations as shown in Figure 4.1. 4.2.2 Describing macro- and micro-habitats The sites used by the birds for the three activities were described at two scales. All foraging, nest and roost locations were assigned to one of three broad habitat types (Table 4'1) to determine patterns of use of habitat at the landscape (macro) scale. These data arc presented as percentage frequencies of each activity within each habitat type. For all nest and roost sites the habitat was also scored in more detail and compared with sites selected at random to test if birds were selecting for specific habitat features. The sampling method was different for nest and roost sites although the micro-habitat features were scored in the same way (see below). Detailed comparisons between the actual sites and random sites were undertaken using ordination (see section 4.2.3). As indicated, foraging sites could not be precisely located on the ground and therefore no detailed sampling of these sites was undertaken. Detailed measurement of nest sites As indicated above, photographs were used to relocate nest sites once nesting was completed to avoid disturbance to the birds. The habitat features of nests sites (Table 4'2) were scored within a circle of 4m diameter centred over the nest site. This sampling area was divided into three concentric bands from the nest (0-0.5m,0.5-1.0m and 1.0-2.0m; Figure 4.2) andinto quadrants to assist with scoring each habitat feature. Mean scores for each concentric band were obtained by averaging scores for each quadrant. Muir's (1977) table, with minor alterations, was used to define the vegetation/lifeform classes present at each nest site. The general substrate on which each nest was placed was also recorded and described. In addition, all the vegetation lifeform/height classes present within a 25x25m (0.05ha) quadrat extending out from each quadrant were listed and their cover density scored 86 Figure 4.1. Location of study sites for investigation of the habitats used for nesting, roosting and foraging by bush stone-curlews Bu¡hìnus grallaríus on Kangaroo Island. E Major Study Siles Ü Minor study siles (nesG enúror roosls only) I NPW sA Reserves N ative Ve gelation 0{020 Kilo mekes E 87 Table 4.1. The three broad habitat categories into which all nocturnal and diurnal locations of bush stone-curlews Burhinus grallørizs obtained from radio-tracking were allocated. Natural Vegetation Including large contiguous blocks of scrub and isolated remnants that were scattered across the study site. Most remnants were in a relatively natural state. Semi-cleared Vegetation Including vegetation that had been modified through partial or complete clearance and had not recovered to its former state. This vegetation was typically more open than natural remnants and lacked either mature overstorey plants or understorey plants. Cleared Land Including introduced pasture and cleared limestone ridges Table 4.2. Edaphic and vegetative variables measured at each bush stone-curlew Burhínus grallarius nest site and associated random sites on Kangaroo Island. Note that all measures of percentage cover were estimated to the nearest five percent for a two metre radius from the nest site, or selected random site (see Fígne 4'2) Substrate on which the eggs were laid (descriptive) Aspect Slope Percentage cover ofbare earth Percentage cover of leaf litter/twigs Percentage cover and number of stones, branches, and stumps (two size classes: small <100mm diameter; large >100mm diameter) Percentage cover of any vegetation lifeform/height present as defined by Muir (1977). Common species present within each life-form (up to three). Total number of lifeform/height classes present (structural diversity) in the vegetation. 88 l I I i i stone-curlew Burhinus I Figure 4.2. Configuration of sampling area for each bush j I grøllørius nest site and associated random sites. Nest sites were positioned at the centre of the concentric sampling bands' I ñB Nol lo Scals 89 according to Muir (1977). The distance from the nest to the nearest plant within each lifeform/height class was also recorded. Detailed measurements of roost sites Roost sites were used more 'loosely' than nest sites and the presence of faeces andlor feathers indicated that the birds often used a small arcarathq than a single site. Therefore the habitat features of roost sites (Table 4.3) were scored for a 10m x l0m quadrat that encompassed the area used for roosting. The vegetation life-form/height classes (Muir 1911) associated with the roost sites were scored in three ways: as a percentage cover class; as a cover/abundance class (Braun- Blanquet cover-abundance scores - see Sutherland 1996); and as a direct count of the number of individual plants present. Not surprisingly these three variables were highly correlated and therefore only the count of individual plants was retained for use in the multi-variate analyses for all lifeform/height classes except for mat plants, grasses and moss. Counts of individual plants within these vegetation classes were not feasible, and therefore the percentage cover class was used instead. The maximum and minimum distances to the edge of the remnants in which the roosts occurred were also measured along with the distances to the north, south, east and west edges. Not surprisingly the maximum and minimum distances were found to correlate with the other distances, and therefore only the maximum and minimum distances were retained for fuither analyses. A1l other variables were included in the multi-dimensional scaling analyses. Selection and measurement of random sites For each nest site and roost site a random site was selected and scored using the same methodology outlined above. Random sites were selected by centring an imaginary grid over the area surrounding each nest and roost site (Figure 4.3). Different sized grids were used for each activity (nests: 0.25ha,50mx50m; roosts: 1.0ha, 100mx100m) to reflect the fact that nest sites were more precise locations, whereas roost sites typically consisted of small areas. Each grid consisted of 100 cells (of 5mx5m for nests and 10mx10m for roosts) and the x and y axis of the grid were numbered from one to ten (Figure 4.3). A random number table was used to select a two digit number that was used as x and y coordinates. These were plotted on the grid to locate random sites. To help ensure that random sites were independent of actual sites only sites that were at least 10m from nests or 20m from roosts were used. 90 Table 4.3. Habitat variables measured for each bush stone-curlew Burhinus grøllørius roost sites and associated random sites. Note that all measures of percentage cover were estimated to the nearest five percent within a 10m x lOm quadrat positioned over the roost sites (see Figure 4'3)' Aspect Size of the remnant of vegetation that the roost was located in Distances to the edge of the remnant (to the north, south, east and west, and maximum/minimum) Percentage cover ofbare earth Percentage cover of leaf litter and twigs, Percentage cover of stones, stumps and branches percentage cover for any vegetation life-form/height as defined by Muir (l9ll) Cover/abundance of each life-form - based on the Braun-Blanquet System (see Sutherland re96) Number of plants present within each life-fornr/height class (number of stems was recorded for mallee trees) Common species within each life-form/height class Total number of life-form/height classes present (structural diversity) Distance to nearest water source (usually a dam) Multiple or single-use site (i.e. was it recorded as being used one or more times) 9I Figure 4.3. The layout of the grid that was 'overlayed' at nest and roost areas to select random sites for sampling. The shaded cell in the grid was centred over nest sites or aligned with roost areas. Random two-digit numbers were used as coordinates to select another cell as a 'random' site. At nest sites each cell represented 5m x 5m, and at roost sites 10m x 10m. The random site was then simply located ìn the ground by measuring the appropriate distances north/south and east/west. N 0r23456189 1 0 S 92 For the few roost sites that occurred under isolated trees random sites typically occurred in open pasture. However, because the birds showed a preference for roosting within (in this case under) vegetation the selection of associated random sites was stratified to exclude points that occurred in cleared areas. In these circumstances the nearest isolated tree greater than2}m from the roost tree was used as the random site. In addition another group of random 'roost' sites were selected within the large and contiguous areas of intact vegetation that bordered the two major study sites (FCHQ, 'KB Downs'). This was undertaken to determine if these relatively intact habitats differed from the remnant patches of native vegetation that existed throughout the study site and were used by the birds. 4.2.3 Statistical analysis of nest and roost site data The aim was to determine if there were differences between sites used by the birds and randomly selected sites. The factors contributing to any similarities/dissimilarities could then be identified, and used to identify features of habitat that might be selected by the birds, if any, Non-metric multi-dimensional scaling (NMS) was the ordination method used because it holds no assumptions about the normality of the data (Clarke and Warwick 1994). In effect the only information used by a successful NMS ordination were the ranks of similarities' This provides a generally applicable base from which to build a graphical representation of the sample pattems, and is intuitively appealing for this reason (Clarke and Warwick 1994), which is one reason why it is arguably the best ordination technique available. The technique also produces a stress value to indicate the relative difficulty with which the samples can be represented. Generally a stress value of less than 0.2 is considered acceptable (Clarke and Warwick lgg4). Clarke and Warwick (1994) provide a good overview of the technique and its strengths and weaknesses. The computer software PC-Ord (McCune and Meffotd 1997) was used to undertake NMS analyses. There were three main stages to the multi-variate analyses of the habitat variables: L similarity Matrix: Spearman's Rho was calculated for each of the pair-wise combinations of variables included (JMP Software, Sall and Lehman 1996). This technique is based on rank scores which suits data with non-normal distributions, as was the case with the data in 'When this study. two variables were very similar (i.e. highly correlated) one of the variables was removed from the data set prior to undertaking the ordination analyses. The variables that were scored more precisely were retained. 93 2. Ordination: The aim of the ordination analyses was to summarise the large multi- dimensional data sets into relatively few dimensions (preferably two providing the 'stress' value was less than 0.2). This allowed the similarity/dissimilarity between sites to be represented visually for interpretation. The relative distance between the sites on the plot represents their similarity/dissimilarity (closer sites were more similar). 3. Final Correlation Matrix: The PC-Ord software also produces a correlation matrix to highlight the key variables determining the similarities/dissimilarities in the ordination space. A visual interpretation of the ordination plot was used to determine if there was any maJor groupings or differences between actual and random sites. 4.3 RESULTS 4.3.1 Macro-habitat Preferences Figure 4.4 shows the percentages of roost, nest and foraging sites that occur within the three broad habitat types across the study sites. The pattern of use of these broad habitat types provides a useful indication of the features within the landscape that are important to the birds. Approximately equal numbers of nests vrere recorded within cleared land and natural vegetation (Figure 4.4), and a smaller number were recorded within regrowth vegetation, indicating that the birds choose a wide variety of sites for nesting. Roost site location showed an expected pattern with most sites located within natural vegetation (60%) and regrowth vegetati on (30o/o; see Figure 4.4). A small number of roost attendance sites were located within cleared land, however, most of these can be attributed to the use of at a nest and/or chick (particularly when nests were located in cleared land), and/or scattered trees (pers. obs.). Foraging (or nocturnal) locations showed a similar, but reverse, pattem to roost sites (Figure 4.4) with approximat ely 70%o of records occurring within the cleared land' The remaining locations were recorded within natural and regrowth vegetation including swampy areas' or around dams (pers. obs). Many of the locations within vegetation can be attributed to the birds attending a nest and/or chick (where nests were located within vegetation; pers. obs.)' 94 Figure 4.4. Relative frequency of use of three broad habitat types by bush stone-curlews Burhinus grallarius for nesting, roosting and foraging. The percentage frequency of sites used by bush stone-curlews are shown for the three broad habitat types located within the study areas, Sample sizes were: nest sites - 27; roost sites - 354; andìoctumal sites - 819. Nocturnal sites are considered to be foraging sites, although the birds were rarely observed and their activity could not be recorded. Natural vegetation includes most remaining vegetation, except for those areas that have been cleared or semi- cleared and consist of regrowth, which forms the second category. Cleared land/pasture includes all cleared land including unimproved areas. Nest Site Locations 50 40 s 30 t) (, g 20 o IL 10 0 lntact Vegetation Semi-cleared Vegetation Cleared Land Roost Site Locations 60 50 â ð¿o o 5530 E g. 20 lr 10 0 lntactVegetation Semi-clearedVegetation Cleared Land Foraging Locations (nocturnal) 70 60 E50 ð40c 9so E ,Ëro 10 0 lntactVegetation Semi-clearedVegetation Cleared Land 95 Also the fact that the birds sometimes remained in the vicinity of their roosts for a short while after dusk, and that all records obtained after dusk were classed as foraging records, would have also increased the number of records in native vegetation. 4.3.2 Micro-habitat selection Nest Sites A total of 27 nest sites were located in the 1995 to 1998 breeding seasons. These nests were located at seven different locations across Kangaroo Island (Figure 4.1), although most were from the major study sites (FCHQ and 'KB Downs'). Five nests were located as a result of radio-tracking and all the others were located by intensive searching. The cryptic and wary nature of the birds made nest-site location difficult, hence the relatively small sample size. The data on ground cover and vegetation life-form/height classes for each of the three concentric rings sampled around each nest site (see Figure 4.2) werc highly correlated. Therefore these data were averaged for all three rings for inclusion into the multi-variate analyses, effectively combining all of the data collected within the two metre radius from the nest. The additional data from the 0.25ha area suffounding the nest site was not highly correlated with these data, andwere included separately in the NMS analysis. The ordination plot resulting from the NMS can be seen in Figure 4.5 (2 dimensions: stress : 0.172). The stress value is moderately high although within an acceptable range to ensure Íhat auseful 2-dimensional picture is obtained (Clarke and Warwick 1994). The stress value was reduced to 0.121 when the NMS was undertaken in 3-dimensions, however, this reduction was not considered great enough to out-weigh the benefits of a 2-dimensional plot. The 2-dimensional plot \ryas therefore considered a useful summary of the sample relationships, and appeared unlikely to be suff,rciently misleading to force its abandonment in favour of the 3-dimensional plot (see Clarke and Warwick 1994). The key variables explaining a high degree of the variance were all located within the 4m diameter circle around the nest. On Axis I the variables were littlerltwig cover and percentage cover of matt plants and on Axis 2 the variables were herbaceous plant cover. Figure 4.5a shows that there is minimal separation between the nest sites and random sites indicating that the random sites were generally similar to the sites chosen by the birds. This is 96 Figure 4.5. The similarities between bush stone-curlew nest sites and random sites on Kangaroo Island as determined by multi-dimensional scaling (a) without site labels and (b) with sites labels. Stress: 0.112 at 2-dimensions. The key variables explaining a high degree of the variance were all located within the 4m diameter circle around the nest. On Axis I the variables were littler/twig cover and percentage cover of mat plants and on Axis 2 the variables were litter/twig cover and herbaceous plant cover. Solid triangles : nest sites; Outlined triangles : random sites located near nest sites. (a) vtVt V A A v VA ^aË VA A VA V V V V V V VV V A AA¡ VV V atr a A A A V V A A (b) DCO2R RR02R V RR03R vrV oc% RROA A CHOlA "^ot^ A RROIR A V CHO1R RRos VA Dcol¡ VA KB03R SDO3R BIO1A KB02R V KBOTR V PDO2R CHOzR V KBOIR *^*o Vn.** V V RR04A V V A K81OR POOlR KAæR KEOOR ì,,^^ V V ^K8O7A KBffiR KB@A sD04 V A¡ KBO3A A KB6A A KBO9A KB04A A A cH0ã re04R A BTOã V V ^ KBl OA PO01^ A 97 not surprising given that a wide variety of positions within the landscape were chosen, including sites in open pasture and sites in vegetation remnants (see Figure 4.4). Figure 4.5b shows the same ordination plot with each site labelled. It shows that some nest sites and associated random sites were very similar and occurred adjacent to each other in the ordination plot. However, some nest srtes were dissimilar to the associated random sites. Despite this the variation in sites used by the birds ensured that when all sites were compared the real and random sites were inter-mixed across the plot, indicating no real differences. Figure 4.5b also shows that the nests from locations other than at the two major study sites (codes pD, CH, SD, BT and DC) are scattered across the plot, and mixed together' This indicates that the types of sites chosen by the birds were available across the landscape and were not specific to any particular location. This is also not surprising given the variety of sites chosen, as outlined above. These results indicate that the types of sites used by birds for nesting are not limited within the landscape. A variety of ground cover was recorded at nest sites and no particular preference was apparent (Table 4.4). Not surprisingly, within vegetation more nests occurred on leaf pasture litter/twigs , and at cleared sites more nests were on moss/matt plants, which includes plants/weeds. All available substrates were therefore used by the birds for nesting, both within vegetation and in cleared areas. Roost Sites Habitat features of 47 roost sites were sampled. Roost sites occurred within remnants of all a sizes as well as within large areas of contiguous vegetation, however, the birds did show tendency to roost towards the edge of the remnants with the minimum distance to the edge averaging 28 metres (Table 4.5). Ground cover at roost sites was variable although litter/twigs cover was consistently high, averaging 70o/o (Table 4'5). This is not surprising given thatg0o/o of roosts were located within vegetation. The distance to water sources did not appear to be important with the average at over 500m. Based on the home range sizes reported in Chapter 3 this would indicate that some birds may not have had water within their home ranges. The ordination plot resulting from the NMS is shown in Figure 4.6' The key variables explaining a high degree of the variance on Axis I were distance to water and litter/twig 98 Table 4.4. The frequency of records of types of ground cover at bush stone-curlew Burhinus grøllørius nest sites (n: 27) on Kangaroo Island. Ground cover types were recorded within a two metre radius of the nest. Combinations of ground cover typ.r are listed as some nests were located on sites where more than one ground cover type had a high percentage cover (>30%). Substrate Type Native Cleared Vegetation Land Leaf litterltwigs 6 I Bare earth 2 I Moss/matt plants 1 4 Stones/exposed limestone 2 a Leaf liuer/twigs/bare earth J 2 Leaf litter/twigs/stones 2 Moss/matt plants/stones I Bare earth/stones 2 Table 4.5. Features of roost sites of bush stone-curlews Burhinus grallarius on Kangaroo Island. Features marked with an asterisk do not include data for all of the 47 roost sites sampled because where sites were located within contiguous vegetation values for these features were not scored. Structural diversity was scored according to Muir's (1977) table of vegetation lifeform/height clas ses. Feature Mean + s.d. Range Size of remnant* (ha) 9t15 0.1-50 Distance to the edge of remnant - minimum (m) 2g+46 0-200 Distance to the edge of remnant - maximumx 174 l.228 0-900 ('") Bare earth (% cover) 14 !22 0-95 Litter/twigs (% cover) 70 !24 5-100 Stones (% cover) 9+14 0-50 Stumps/branches (% cover) 6+9 0-30 Structural diversity (no. of strata) 3.6 r 1.9 1-9 Distance to water (m) 519 t292 10-1000 99 00I A ol V V V YV¿ ¡ A V VA o YA 0 a AY O vvf 'rS 0 A A O ¡A . AA ^a A Y VV o vv ¡V O V A A 0 A A n a¡ O A Y O V A V ¡ O O O A Y A A V O O a Y (q) Y A V A A V o OV o A o ^ryoAV o Ay + V AV V o (e) 'su,r.roq tIX pue sre¡unbpeeH ìred es€qC srâpurlú le sells ,(pnrs ¡oleru eql Sutpunolns uorlele8err e^B€u ruo4 selrs tuopueJ : selcJrc prlog iselts lsooJ Jeeu pâlecol sells luopueJ : se18uerr1 peurllno lselrs lsoo¡ : se13ueu1 pr1os 'luese¡d ele¡ls uoqeleSe,t ¡o Joqrunu pue Je^oc Erlq¡regr¡ 'reprn o1 ecuelsrp orew Z srxy uo pu€ Je^oc 3tm17rept1 pu€ JeleÀ\ 01 ecuslslp eJe^\ I srxv uo ecu€rJe^ eqlJo eerSep q8H e Suruteldxe selqelJe^,(e¡ eq¡ 'suolsuerulp-ZW pê^oueJ srerllno eq] q]yy\ ggl'0 : pu€ lsuorsueurtp-z ]e ç60'0 : ]es-elep e1e¡duroc erÛ roJ sse4s 'pa^ourer srelllno ¿ aql qlptÀ (q) pu¿) les-Blup a¡e¡duroc (u) :8u¡¡ues ¡uuolsuarulp-Illnur ztq pau¡rurelep su pu¿Isl ooreãuu;¡ uo sells tuopu¿I puu sells lsoor srytnpol8 snu!rytng ÀrelrnJ-auots qsnq uea,tqaq se¡llJullur¡s eqI '9'7 arnã¡¡ cover and on Axis 2 were distance to water,litterltwig cover andnumber of vegetation strata present. The presence of seven outliers (see Figure 4.6a) forced all other sites to clump together, making interpretation more difficult. These outlying sites were primarily separated on the basis that they had large trees present but no mallee, and consisted of three pairs of roost sites and associated random sites, and one random site from the natural vegetation surrounding the study areas. These outliers ìwere removed to obtain a better resolution for the other sites and the resulting ordination plot can be seen in Figure 4.6b. The results are similar to those for the nest sites and the similarity between the roost and random sites is obvious (Figure 4'6b), with all sites inter-mixed across the plot. Therefore based on the variables measured there is little difference between the sites chosen by the birds and nearby random sites. Based on number of lifeform/height classes present the random sites sampled within natural vegetation surrounding the main study sites had a greater structural diversity than the paired roost and random sites (mean * s.d.: 6.9t1.6 [n:20] strata for intact vegetation; 3'6tl'9 [n:94] strata for paired roost and random sites). Despite this obvious difference, Figure 4'6b shows that these sites were not completely dissimilar to the other roost and random sites. However, they are primarily clumped on the edge of the ordination space rather than being mixed through the other sites suggesting that they are towards the edge of the spectrum with regards to the types of sites surveyed. Observations suggested that these sites were less suitable and this is discussed below. The results indicate that bush stone-curlews appear to be using the remnant vegetation within the farming areas for roost sites with little regard for any specific attributes. 4.4 DISCUSSION The broad habitat use recorded in this study was expected, and is similar to that recorded in other studies (eg. Johnson and Baker-Gabb 1994). Figure 4.4 clearly shows that on a landscape scale natural vegetation remnants are important for providing roost sites and cleared land is important for providing suitable foraging habitat. Nest sites are located in both of these habitats. The majority of the data collected for this study were obtained from two study sites located in the south-west of Kangaroo Island. These study sites are slightly atypical of much of the 101 broader agricultural landscape across Kangaroo Island, being completely surrounded (FCHQ) or surrounded on three sides (KB Downs), by large expanses of natural vegetation. However, despite this the major habitat components of each site (i.e. cleared land, natural vegetation and regrowth vegetation) were typical of the habitats occurring across the agricultural landscape on Kangaroo Island. The NMS analyses of nest and roost site data (Figures 4.5 and 4.6) support this with sites located away from the two major study areas mixing amongst these sites. Combined with the wide distribution of the birds on Kangaroo Island (see Chapter 2) this suggests that the birds are likely to use similar habitats right across the island. Some minor differences may result from the fact that the overall percentage of native vegetation cover decreases from west to east, and remnants are generally smaller (pers. obs)' Although this may affect the densities of birds it is not expected to greatly alter the birds' choice of sites. 4.4.1 Nest Sites Bush stone-curlews were less specific in regards to choice of nests sites compared to roost sites with vegetation remnants, regrowth vegetation and cleared land all selected. Nest sites were relatively difficult to locate and therefore the sample size was quite small (27)' However, the range of broad habitats in which nests were located suggested that observations were not biased by differential detection rates within each habitat type (pers. obs.). Given the broad range of sites selected as nest sites it was expected that overall random sites chosen around nest sites were likely to be simil ar, and the NMS analysis confirmed this. The results suggest that the types of sites chosen by the birds are not limited across the landscape. The habitat recorded at nest sites was similar to other studies, where nests were often placed under trees in open woodland (i.e. in remnant native vegetation) and often near dead timber (Marchant and Higgins 1993). Johnson and Baker-Gabb (1994) found that nests were consistently in rather open areas , avenging 12.7m away from trees, although this is likely to be a reflection of the nature of remaining native vegetation across their study site. Little other data exist within the literature for further comparisons. In all cases where radio-tagged birds were recorded breeding (n:5), nests were invariably located in the vicinity of the birds' roost area (within tens of metres, pers' obs.). Although the specific factors determining nest site selection are not known these data suggest that the birds simply chose sites in the vicinity of their roost areas. Familiarity with these sites, often as a 102 result of long-term use, may provide a sense of security to the birds, which may be just as important as the specific features of the nest site itself. Nest sites were positioned on a variety of substrates including leaf litter, moss, pasture plants and bare earth, or combinations of these (Table 4.5). There was no substrate that appeared to be preferred by the birds, and in reference to the discussion above the substrate chosen was probably just a reflection of what occurred around roost sites' Based on these data, nest sites on Kangaroo Island do not appear to be associated with specific features within the landscape. In fact the birds nested almost anlruvhere, except in vegetation with a dense understorey. Potential nest sites therefore appeared to be unlimited within the areas used by the birds. Disturbance factors may influence the choice of nest and roost sites as much as habitat per se within the range of the birds on Kangaroo Island. 4.4.1 Characteristics of roost sites Roost sites were typically located in natural vegetation including remnants of varying sizes (as small as Q.lha), near the edges of large contiguous vegetation, and less frequently under isolated trees, or groups of trees. One feature that was typical of most roost sites was that the vegetation was quite open, and in particular, low shrub layers were often lacking (pers. obs.). This observation was supported by comparing the average number of lifeform/height classes (Muir lg17) recorded at roost sites (3.6+1.9) with random sites in nearby areas of natural vegetation (6.9 t 1.6). The NMS analysis undertaken on these data (Figute 4'6) did not highlight structural diversity as being signif,rcant. However, they did suggest that sites were slightly different from most of the paired roost and random sites, being predominantly clumped towards one edge of the ordination space. This is probably a reflection of the gteater structural diversity within the vegetation at these sites. Despite the lack of lower shrub layers, most sites had good canopy cover of taller shrubs or mallee trees (pers. obs.). The number of stems associated with these mallee trees aná shrubs was high, and these provided excellent camouflage for the birds. Locating and observing the birds within these remnants was very difficult þers. obs.). Therefore, in general, the roost sites provided good cover from above, and also allowed for near unrestricted vision at ground level, both of which helps to ensure that predators are detected and/or avoided. 103 The preference for open woodland/mallee areas probably reflects the nature of the available habitat within the agricultural landscape. Most remnants are modified as a result of practices such as grazing,with a resulting loss of structural diversity. Some remnants were also located on limestone ridges that were unsuitable for agriculture, and the poor shallow soils limited vegetation diversity (both structurally and floristically). However, this may benefit bush stone-curlews for the reasons mentioned above. The roost sites recorded in this study were similar to those observed elsewhere. Marchant and Higgins (1993) recorded bush stone-curlews as roosting among leaf-litter, clumps of trees, and in or adjacent to more open habitat such as savannah. Johnson and Baker-Gabb (1994) found that day shelters used by the birds had a higher percentage of debris fallen from trees, and that there \¡r'as more bare ground, lower grass and less disturbance from farming than in surrounding areas. Their study was undertaken in northern Victoria where much less vegetation remains, and remnants typically only had grass in the understorey, which provides little cover. A preference for areas with more tree debris and less disturbance in these areas was not surprising. The relatively high percentage of vegetation cover, and condition of the remnants (most have at least one shrub layer, even if they have been gtazed) makes the situation on Kangaroo Island different, but specific features such as these were not identified as being important for the birds in my study. These data suggest that most of the vegetation remnants located within the agricultural landscape on Kangaroo Island provide potentially suitable habitat for roost sites for bush stone-curlews. Various factors may contribute to some remnants apparently not being used (e.g. conspecific intèractions, spatial arrangement of remnants and breeding territories), however, over time most remnants are likely to be used as some birds regularly shift between roost areas (Chapter 4). Johnson and Baker-Gabb (1994) recorded this pattern of use for small remnants in northem Victoria, where some birds v/ere observed to regularly shift between several remnants within a small area. Movements may occur aftet a disturbance, or in the case of the mainland, may reflect a predator avoidance strategy, as sites used for a long time invariably acquire a build-up of faeces, which may alert predators (especially foxes) to the presence of the birds. Also the factthatmost roost sites in this study were located using radio-tacking, and that only a small proportion of the population at the study site were radio- tracked þers. obs.) suggests that many other sites used by the birds would have gone undetected. Also within the sites chosen there was considerable heterogeneity and the characteristics of the remnants that were apparently not used did not appear to be different to 104 those that were used þers. obs). These factors suggest that the birds would have used many more reÍtnants than just those in which they were detected, and it is probable that the majority of remnants would provide potential habitat for the birds. 4.4.3 Foraging (nocturnal) site selection Difficulty in observing stone-curlews at night meant that the only means for locating them was radio-tracking, and the triangulation technique. This meant that the birds were tarcIy observed, and therefore nocturnal fixes obtained could not specifically be labelled as foraging fixes as the birds may have been engaged in other activities. However, for the purposes of the study I have considered nocturnal fixes to indicate where foraging occurred' Most foraging locations occuffed within cleared land (Figure 4.4) which predominantly consisted of improved and unimproved pasture. Fewer records were obtained within regrowth vegetation, sedgelands and swamps, and dams. Approximately 20o/, of locations were within the vegetation remnants, but these would have included locations of birds that had not left day-time roosts to commence feeding. Other studies reflect this choice of foraging sites with bush stone-curlews recorded foraging on dry open ground, sometimes under woodland trees, among grass, pasture or crops, in irrigated paddocks, watercourses, dams or swamps (Marchant and Higgins 1993). A wide variety of sites are therefore used by the birds for foraging, with most of these sites occurring in naturally open aneas) or areas where the natural vegetation has been cleared. 4.4.5 Conclusions The habitat selection by the birds shows a clear preference for agricultural areas and therefore ample suitable habitat is available for bush stone-curlews on Kangaroo Island. Foraging habitat has in fact been provided by the clearance of native vegetation, and the remaining remnants of native vegetation provide suitable habitat for nest sites, and particularly roost sites. There is an apparent lack of specific habitat requirements within this agricultural landscape. The wide distribution of the birds (see Chapter 2) and their relative abundance (Joseph 1983, Baxter 1995 and this study) support this. Kangaroo Island is unlikely to have supported many bush stone-curlews in the period prior to European settlement and the clearance of the land. The absence of the birds from large areas of intact habítat, such as in Flinders Chase National Park (see Chapter 2) supports this. This large remnant, with its dense understorey, presumably provides an indication of the nature of 105 the vegetation which originally covered much of the island. Clearly the bush stone-curlews have done well on Kangaroo Island due to the opening up of this habitat for agriculture, and because ofthe lack offoxes. This study provides fuither circumstantial evidence that the absence of foxes on Kangaroo Island is the major factor contributing to the birds' abundance on Kangaroo Island. As indicated in the introduction, although a high percentage of natural vegetation cover remains on Kangaroo Island, and this vegetation is relatively intact compared to the mainland, the features of this landscape are similar to those on the mainland. The removal of foxes would potentially allow these birds to establish across much of their former mainland range and this is being tested by projects on the mainland aimed at removing predators. Already several such projects exist, including Operation Bounceback in the Flinders Ranges, 'Ark on Eyre' on Eyre Peninsula and the Arid Ecosystem Recovery Project near Roxby Downs' These projects are providing environments that are predator free and should be targeted for returning these enigmatic birds to areas of their former range' Clearly, whilst the requirements of the birds appear not be very specific, areas without cleared land, such as Flinders Chase National Park, and areas with very limited vegetation cover, have less potential as habitat for bush stone-curlews. There may be brief periods when large areas of vegetation become suitable, such as afterlarge wildfires. On the other hand small land-use changes (e.g. planting of crops) may have detrimental impacts on the birds in the short-term through the loss of suitable foraging habitat, and/or a reduction in prey abundance. This alone is not likely to severely impact on the population, however, broadscale landscape changes are of greater concern. Kangaroo Island is currently undergoing a major change in land-use with large areas of cleared land on the western end of the island being converted to forestry plantations. This is likely to have a major impact on the bush stone-curlews present within these areas and is discussed further in Chapter 6. 106 CHAPTER 5 DIET AND FOOD RESOURCES 5.0 INTRODUCTION Consideration of diet is an important component of any comprehensive ecological study. Food availability is often the single most important factor that influences the abundance of a species (White 1978, Sinclair 1989, Boutin 1990). Food has often been the environmental variable that sets the upper limits for population size, suggesting that other factors such as intra-specific competition, predation and weather combine to keep populations below the potential size suggested by food availability (V/hite 1978, Sinclair 1989, Boutin 1990). Information on food items of animals also provides practical information that can help to facilitate conservation and management, to assess economic impacts on humans, and to determine potential for uptake of contaminants (Brown and Ewins 1996)' Bush stone-curlews are widespread and common across Kangaroo Island (see Chapter 2) despite significant declines across much of mainland southern Australia. The absence of foxes from the island is considered the main reason for their abundance, but the clearance of native vegetation has also been less severe than on the mainland, and has opened up otherwise unsuitable habitatfor these birds. Bush stone-curlews are nocturnal and are thought to obtain their food from the ground by gleaning surface features, or probing soft soil (Marchant and Higgins 1993). On Kangaroo Island bush stone-curlews demonstrate a strong preference for foraging in open pastured areas, or semi-cleared areas (see Chapter 4), possibly because these areas provide easier feeding opportunities, being more suited to their foraging habits' However, the nocturnal activity of bush stone-curlews makes it difficult to undertake detailed study of foraging habits in order to confirm this. The modified habitats may also provide higher food levels as a result of pasture improvement, including the addition of fertilisers. However, the bird's reliance on such areas for foraging potentially puts them at risk from agricultural practices. Changes in land-use, such as annual cropping, directly reduces the available area of foraging habitat, and the use of pesticides may effect the birds directly, or indirectly through reductions in food supply. Before the effects of these agricultural practices can be determined it is necessary to investigate the diet and food supply of bush stone- curlews. 107 This study aimed to determine the diet of bush stone-curlews through examination of faeces, and to compare food selection to potential food resources captured in micro-pitfall traps located within foraging habitat. Answers to the following questions were sought: 'What 1. taxa arc important food items for bush stone-curlews? 2. Does the diet vary between locations (i.e. spatially) and between seasons (i.e. temporally)? .What 3. food resources are available at the major study sites and how do these change temporally? 4. How does the diet of the birds compare with potential prey resources? 5.1 BACKGROT]ND INFORMATION 5.1.1 Other studies on the diet of bush stone-curlews The diet of bush stone-curlews is known from studies of crop contents, pellets and faeces and a range of anecdotal observations (see Marchant and Higgins 1993). Food mainly consists of insects, molluscs, centipedes, crustaceans, spiders, frogs, lizards and some vegetation and seeds (Table 5.1). The data indicate that almost all prey items are ground/surface dwelling and so studies of diet should concentrate on sampling this fauna. Diet is thought to differ little between seasons throughout the range of bush stone-curlews in Australia, but no extensive studies have been undertaken. 5.1.2 Techniques for determining the diet of birds One of the most commonly used techniques for assessing the diet of birds is faecal analysis (e.g. Calver et al. 1978, Wooller and Calver 1981, Paton1982, Moreby 1988, Baker-Gabb 1988, Green and Tyler 1989, Van Horne and Bader 1990, Dickman et al. 1991, Danks and Calver lgg3). This technique is commonly used for birds that are known to take arthropods and/or vertebrates as prey items. Faeces are collected from roost sites, nest sites or captured birds and the contents are teased apart and examined under a binocular microscope to determine the types of food eaten. The various prey items can then be recorded on the basis of their presence and absence within each faecal deposit (i.e. percentage frequency), or alternatively the prey remains can be counted to give a quantitative estimate of the insects eaten (Calver and Wooller 1982). 108 Table 5.1. List of food items recorded for bush stone-curlews Burhinus grallørizs from published literature . Source: Marchant and Higgins, 1993 ffi Gastropoda Crustacea Arachnida Araneae Spiders Scorpiones Scorpions Insecta Blattodea Cockroaches Orthoptera Tettigoniidae Bush crickets Gryllidae Crickets Gryllotalpidae Mole crickets Acrididae Odonata AnisoPtera Dragon flies Blattidae Cockroaches Mantodea Mantidae Praying mantids Dermaptera Earwigs Hemiptera Reduviidae Assasin bugs Pentatomidae Shield bugs Cicadelidae/ Leafhoppers Eurymelidae Miridae/ Bugs Lygaeidae Berytidae Stilt bugs Belostomatidae Water bugs Others Coleoptera Carabidae Ground beetles Scarabaeidae Scarab beetles Elatridae Elongate beetles Tenebrionidae Beetles Chrysomelidae Leaf beetles Curculionidae Weevils Lucinidae Beetles Amycterinae Weevils Lepidoptera Moths and butterflies Noctuidae Moths Hymenoptera Wasps and ants Ichneumonidae (parasites oflarvae) Formicidae Ants Rhytidoponera Iridomyrmex Camponotus Chilopoda Centipedes Oligochaetes VERTEBRATES Mus domesticus House Mice Amphibians Hylidae Frogs Bufo marrnus Cane Toad Limnodynastes tasmaniensis Litoria gracilentia Litoria nasuta Scinicidae Skinks 109 Techniques for assessing the length, dry weight and energy contents of prey items are also available (Calver and Wooller 1982). A similar technique, predominantly used for birds of prey such as owls, is pellet analysis (e.g. Morton 1974, Yalente 1981, Estbergs and Braithwaite 1985, Steenhof and Kochert 1985, Atkinson and Cade 1993, Lundie-Jenkins 1993). Direct observations can also provide useful information on diet (e.g. Calver and Wooller 1982, Paton lg82). Less commonly used techniques include collection of birds for stomach analysis (Wooller and Calver 1981, Paton !982, Booth 1985, Dostine and Morton 1989a, Dostine and Morton 1989b) and stomach flushing (Gales 1987, Major 1990), including the use of emetics (Montague et al. 1986, Montague and Cullen 19SS). These techniques receive more use with seabirds. Collecting birds or saline flushing of stomachs may have negative impacts on the birds being studied (Calver and Wooller 1982). The use of emetics to encourage regurgitation may have a high casualty rate (Jenni et al. 1990). With all of these techniques care must be taken when analysing and interpreting the results. It is necessary to be aware of biases resulting from differential digestibility of prey items, which can lead to over or under-estimation of prey types. Major (1990) notes that with regards to stomach flushing large prey may be less readily regurgitated, but will remain in the stomach longer, and soft bodied prey should appear more readily in flushings but should also disappear from the stomach quicker. Also, not surprisingly, hard parts should be better represented in stomachs. Most of these factors are also true for remains found within faeces (Major 1990). To account for differential digestion rates of prey items correction factors have been used. In most cases these have been determined by feeding captive birds known numbers of prey items and analysing the remains obtained from both stomach flushing andlor faeces (e.g. Coleman l974,Custa and Pitelka 1975, Green and Tyler 1989, Jenni et al. t990, Major 1990). Green and Tyler (1939) determined the diet of the stone curlew Burhinus oedicnemus by faecal analysis after trials with captive birds. Their results showed that the proportion of sclerotinized arthropod structures that were recovered were relatively uniform (approximately 60-g00/0), except for mandibles of ground chafer and spiders, which had lower recovery rates' The proportion of earthworm chetae recovered was also low. Green and Tyler (1989) also determined that recovery rates appeared to be independent of size, except for millipedes and earthworms. This information is particularly useful for this study. 110 Despite the problems with interpreting the contents of faeces the technique is widely used because it is relatively simple to undertake and the impacts on the study animals are negligible. A sound knowledge of the limitations of this technique ensures that results can be interpreted appropriately. Studies have found that faecal analysis agrees well with observations on the incidence of insectivory and the types of insects eaten (Calver and Wooller 1982), and although validation has only occurred for a few species, the information from these studies helps with the interpretation. 5.1.3 The use of micro-pitfalls to assess abundance and diversity of ground-dwelling invertebrates Micro-pitfall traps provide an effective technique for sampling potential prey items of bush stone-curlews. These traps are widely used in studies on ground-dwelling invertebrates and are used to compare community structure or population size, both spatially and temporally (Luff 1975, Topping and Sunderland 1992, Abensperg-Traun and Steven 1995, Bromham et al. !999, Melboume lggg). The relative simplicity of this technique has ensured its frequent use in ecological studies, although there is widespread recognition of potential sources of bias with this technique (Luff 1975, Southwood 1978, Topping and Sunderland 1992, Sutherland 1996, Melbourne l99g). Trap size, shape and trap materials, and the type of preserving fluids used can all influence captures in these traps. Studies have suggested that trap efficiency varies between species of invertebrates, between habitats, with weather conditions, and with the physiological state of the animal (Baars 1979). Of these factors the importance of habitat strucfure on trappability, which can influence data particularly where studies compare locations with different habitat structure, or where habitat structures change in time, is often overlooked (Melboume 1 999). Population density and trappability of a species combine to influence capture rates in micro- pitfall traps. Biased estimates for data at the population level can result from spatial and/or temporal differences in trappability. Activity levels of individuals are one well recognised influence on trappability, and micro-pitfall data are often said to represent the activity density of a population (Melbourne 1999). Activity level can be affected by a variety of factors, such as weather, leading to biased estimates of population density. The same problems exist for community-level data. This occurs as a result of differences in activity levels or through trap avoidance or escape behaviour (Luff 1975, Topping 1993, Melbourne 1999)' 111 Fortunately these limitations are not critical when comparing relative differences in population density and/or community structure, both temporally and spatially, as biased data are suff,rcient to address differences (Melboume 1999). Hovrever, this implies that the biases must be the same between the times or locations being sampled. This assumption is reasonable for spatial comparisons, especially if weather conditions are the same for all sites sampled, however, for changes in time (e.g. seasonal comparisons) changes in weather conditions and animal activity may corïupt this assumption (Melboume 1999). In particular, where sites with different habitat structure are compared the assumption that the biases are the same is critical, as habitat structure must not influence trappability (Melbourne 1999)- Influential elements of habitat structure could include vegetation density, roughness of soil surface, or the spatial alïangement of micro-landscape features. These directly affect trappability by impacting on the movements on an animal, either physically or via micro- climatic effects. Very few experimental studies to examine these effects have been undertaken (see Greenslade 1964, Melbourne 1999). 5.2 METHODS 5.2.1 Collection and analysis of faeces Faeces were collected from known roost areas of bush stone-curlews fitted with radio- transmitters (see Chapter 3), and opportunistically at other sites where birds were flushed during the day. The majority of faeces were collected at the two major study sites, Flinders Chase Park Headquarters (FCHQ) and a nearby agricultural property 'KB Downs', with some faeces opportunistically collected at another nearby property, Brookland Park (Figure 5.1)' Individual faeces were placed within small snap-lock bags, labelled with date and location, and frozen. The methods for analysing faeces described by Calver and'Wooller (1982) and Moreby (1937) were followed. Each faeces was placed within a small plastic vial and saturated in 70o/o alcohol before being broken apart by shaking the vial vigorously. The contents of each vial were poured into a modified 90mm plastic petri-dish and viewed through a binocular microscope set at 10x or 20x magnification. Identifiable fragments of exoskeleton, mandibles and skins were identified and recorded to Order (hereafter referred to as food groups). These groups will be referred to throughout this chapter by their common names (e.g. beetles, spiders, ants, etc.). The frequency of each food tt2 Figure 5.1. Locations of the study sites for the study of the diet of bush stonecurlews Burhínus gralla¡íus. f NPUí SA Resarws f Hatiu Vegetrtion 0 5 l0 l5 Kihmelets 111 group within each faeces was recorded. As anticipated much of the material present consisted of fragments of insect cuticle and other debris that was difficult to attribute to particular taxa' However, identif,rcation was assisted by referring to vouchers collected from micro-pitfall 'Wooller traps (see below), as well as information provided within Calver and (1982) and Moreby (1988), and by consulting entomologists from the South Australian Museum. 5.2.2 Sampling of invertebrates within areas used for foraging by bush stone-curlews Micro-pitfall trapping was undertaken to determine the relative diversity and abundance of potential prey items present within the areas used by the bush stone-curlews for foraging. Micro-pitfall traps were established at eight sites, three at FCHQ and five at 'KB Downs' (see Figure 5.2). Sites were chosen based on known locations where the birds had been observed at night while spotlighting, and also from radio-tracking results (see Chapter 3). At each study site the available foraging habitat was stratified and sampled according to its prevalence. At 'KB Downs' two sites were located within semi-improved pasture, two sites were located on low limestone ridges, and one site was placed within a low-lying arca that Park became water-logged, and partially inundated during winter. At Flinders Chase National Headquarters one site was placed in a cleared area with native couch Sporobolus spp. and native iris Orthrosanthus multiflorus one site was placed within a low-lying ateathat became water-logged and partially inundated during winter, and one site was placed in semi-cleared open low woodland. Nine micro-pitfall traps measuring l25mm in diameter by 130mm deep were placed in a cross-pattern at 10m intervals (i.e. diameter of 40m) at each trap site (Figure 5.3). At each site permanent pots with lids were placed in the ground at the beginning of the study to minimise ,digging-in' effects (Greenslade 1973). When trapping occurred a second temporary pot was inserted into the permanent pot, and then removed at the completion of each sampling period. Lids were placed on the traps between trapping sessions. Each micro- pitfall was marked with a piece of fencing wire stuck into the ground with reflective tape placed on it to reduce the likelihood of the traps being driven over at night' Each site ,was opened for five nights at intervals of approximately six weeks' Two to three centimetres of 70Y" alcohol were placed in each trap, and this was topped up as necessary after evaporation. The micro-pitfall traps were only opened at night, with lids being removed tt4 6KB Figure 5.2. Locations of micro-pitfall trapping sites at Flinders Chase Park Headquarters and l)owns'. Micro-pitfall locations are shown as red circles. Flinders Chase National Park Headquarters (FCHO) 'KBDowns' É r,Ís$m+ L¿n drover Lsn dc over R €m na nt v êg etation R êm na nt Veg etâlion i+i¡Þ Í*l¡Ì (overstorey onV) . Rêmn¡ntVeget¡t¡on(understorÊymodlled) Reglowth Vegét¡tlon R eg Veget¡t¡o o (u nde rstorey o nly) ßegrowth Vegel¿tion rowth W Sw¡ mp Sc dges Pl¡nted Tr€es "¡ì)rti Pines I I Clêerêd L¡nd R eveO Ét¡t¡on I D¡ms o 200 Meters C lê ¡red 0 100 2fþ MetÊrs I 100 D ¡ms 115 Figure 5.3. Configuration of micro-pitfall trap sites. North o1 10m c2 o6 o7 o3 o8 o9 40m o4 o5 116 within one hour of dusk and replaced within one hour of dawn. This prevented the capture of animals that were active during the day, and prevented birds such as ravens from tampering with the traps and their contents. Within a week of each trapping session the contents of the traps were sorted and identified to 'Within Order (these will be referred to as prey groups). abundant and diverse groups of invertebrates, such as beetles, ants, and spiders, individuals were identified to morpho-species by assigning numbers to each morphologically distinct species (e.g. Coleopteta l, Coleoptera 2, etc.). Other less numerous groups were clumped based on similar morphology and síze (e.g. larvaelcaterpillars and moths). Vertebrates were identified to species. The few invertebrates that were less than one millimetre in diametet, andlot less than three millimetres in length were discarded, being considered too small to be sought after by the bush stone- curlews. This is consistent with the sizes of the animals in Table 5.1 þers. obs.). 5.2.3 Data analysis All data were entered into a Microsoft Access database and imported into Microsoft Excel to assist with analysis and data presentation. It was determined that the same food groups identified in faeces could also be used to define prey groups captured in micro-pitfall traps, 'Within and this helped to facilitate comparisons. these groups, several were clumped to increase sample sizes. The data-set was analysed for differences between invertebrate fauna and diet at study sites using the Bray-Curtis test of similarity and an analysis of similarity (ANOSTM). Faeces Data Data for food groups found in faeces is presented as percentage frequency of occurrence within all the faeces, by study site, and by season' To statistically compare the diet between the study sites ten faeces were randomly selected from each season at each site and the presence/absence of each major food group was recorded (see Figure 5.4). A total of 40 faeces were therefore selected from both 'KB Downs' and FCHQ, while 20 were sampled from 'Brookland Park' as faeces were only collected during two seasons. The total number of faeces selected was also limited by the capabilities of the analysis program (Clarke and Gorley 2001) and by the lowest number of faeces recorded at any site for a season (which was l3 at 'KB Downs' in autumn). tI7 Micro-pitfall Data Most morpho-species were not collected in sufficient numbers to warcant individual treatment. Also, although each morpho-species was assigned to a síze class to allow grouping of the data within each prey group based on size, in most cases sample sizes were too small within each prey group to allow for reasonable comparisons. Therefore all captures were clumped solely by prey groups for data presentation and analysis' Trap effort was not equal for each site so the data are presented as captures per trap-night (captures per trap-night) rather than total captures. This allowed for direct comparisons between numbers of animals caught and the community structure between sites. For seasonal comparisons between captures at each site, data from two trapping sessions (a total of 10 nights) per season were analysed. At 'KB Downs' an extra session was undertaken, however, this session straddled autumn and winter, making it difficult to attribute to one season, and was not included in seasonal comparisons. Also at FCHQ one site only had one trapping session for winter, so to rectify this, data were doubled. 5.3 RESULTS 5.3.1 Prey items recorded within faeces A total of 416 faeces from three locations were collected and analysed during this study between 1995 and 1998 (see Table 5.2). The numbers of faeces collected during each month at eachsite was not equal as faeces were only collected opportunistically. The bush stone-curlews clearly consumed a wide variety of food items including beetles, spiders, ants, earwigs, larvae/caterpillars, moths and some vertebrates (Figure 5.4)' Most faeces contained two or three food groups (Figure 5.5), with up to six different groups being recorded within some individual faeces. This, combined with the wide variety of food groups recorded, suggests that the birds are opportunistic foragers, consuming whatever prey they come across The remains of beetles were the most commonly recorded prey item, occurring in over 90"/o of all faeces (Figure 5.4). Three other food groups also occurred frequently (atbetween 25Yo and 50%): spiders, ants and lawaelcaterpillars. The only exception to this was that ants were recorded a lot less frequently at 'Brookland Park', although this primarily reflected the timing 118 I l Table 5.2. Numbers of bush stone-curlew faeces collected from three locations on Kangaroo Island between 1995 and 1998 in each month of the year. Months Faeces were Collected Site JFMAMJJAS O N D Totals FCHQ 23 l0 t7 16 37 39 16 22 7 4 t9L a 'KB Downs' 2l 25 1 1,2 J 27 42 2 24 t57 a4 'Brookland Park' t9 1t 10 68 I t 119 Figure 5.4. Percentage of bush stone-curlew Burhinus gralløríus faeces containing the remains of different prey groups at Flinders Chase Park Headquarters (n : 191)' 'KB Downs' (n: 157) and 'Brookland Parkt (n:68), on western Kangaroo Island. 100 90 80 ð70 FCHQ tr ¡ o KB Downs o+60 ¡ L50 o g Brookland ct) (E Park Ë40 o o bso o- 20 10 0 f ¡e¿ ;\ø a.t" ."'- d,Ñ $"o' øa- .O.r.""* 720 Figure 5.5. Percentage frequency of total numbers of prey groups recorded within individual bush stone-curlew Burhínus grøllarius faeces collected for three sites on western Kangaroo Island during 1995-1998. 65 60 55 50 45 ¡FCHQ >' 40 tr35o ¡ KB Downs o g Brookland o3so Park L¿. 20 15 10 5 0 2 34 5 6 Number of Food GrouPs t2r of collection of faeces at this site (September and October), when ant actívity was relatively low (see section 5.3.2). All of the remaining prey groups were recorded in less than 25o/o of faeces, although centipedes/millipedes, earwigs, moths, snails and vertebrates all contributed measurably to the composition of the faeces by volume þers. obs.). Scorpions \ryere recorded in only 2o/o or less of faeces, and worms were not recorded at al7, although they were included in Figure 5.4 for ease of comparisons with micro-pitfall capture data. Vertebrate prey items were recorded in approximately l5o/o of faeces at FCHQ and Brookland Park, and approximately 5o/o of faeces at 'KB Downs'. This prey group consisted almost solely of frogs (species not determined), although at least one house mouse Mus musculus was also recorded in the faeces. Soil and plant material was also recorded in approximately 25o/o of faeces, and urea was recorded in most faeces. The consumption of soil and plant material was thought to occur coincidentally with the consumption of other food. Figure 5.6 shows the frequency of each prey gïoup for each season for FCHQ and 'KB Downs'. Faeces were only collected at 'Brookland Park' in three separate months (and two seasons) and therefore these data arc not included. Faeces were attributed to seasons based on the month in which they were collected, but they were not all collected within the same year' Not surprisingly beetles were recorded in greater than 90o/o of all faeces in all seasons at both sites, except for FCHQ during winter (Figure 5.6). The occuffence of most other prey groups showed greater seasonal variation for both sites. Variation between sites is also evident, and probably in part reflects the differences in the occurrence of each prey group at each site (see below). Spiders occurred in greater than 20Yo of faeces in all seasons at both sites, and peaked in occuffence in spring, especially at FCHQ where they occurred in over 60'/o of faeces (Figure 5.6a). At FCHQ ants occurred in at least 25o/o of faeces, and showed an obvious trend from winter through to autumn where occuffence peaked at70%o (Figure 5.6a). This trend was not 122 Figure 5.6. Seasonal variation in the percentage frequency of prey items recorded within bush stonecurlew faeces at (a) Flinders Chase Headquarters and (b) KB I)owns. (a) 100 90 80 oc trWnter o 70 (n=76) 3 C' 0, 60 6 Spring lr (n=45) o 50 E' r! 40 I SunrrBr oE (n=37) cl 30 o lAuturm À 20 (n=33) 10 0 *" {,'*t" .1*""O "."" .E *S "ê' (b) 100 90 () 80 c tr\Mnter o 70 (n=30) C'= t- g 0, 60 Spring l! (n=44) o 50 Er I Sunrrer .! 40 c (n=70) 0, 30 C' lAuturm o (n=1 3) G 20 10 0 ** $"t' "."" .E *S "** .$".Ñ.1""Y 123 apparent at 'KB Downs', although ants were recorded in greater than20%o of all faeces except in spring, where their occurrence fell to 5Yo (Figure 5.6b)' Earwigs were recorded a lot more frequently at FCHQ, and occurred in greater than l}Yo of faeces in all seasons. In contrast at 'KB Downs' this food group was only recorded in two seasons (winter and summer) and in less thanI}Yo of faeces (Figure 5.6b). The patterns for all other food groups within the faeces are broadly similar for each site. Centipedes/millipedes, snails and lawalcaterpillars all occurred in similar frequencies and showed similar seasonal trends in occurrence at both sites. Moths were only consumed in spring and summer at 'KB Downs' and occurred in 18% and 360/o of faeces respectively. They were also absent in winter at FCHQ, but showed a marked peak of occurrence in spring, of over 30%. The pattem for vertebrate occurrence in faeces was quite different between the sites. FCHQ showed a much higher frequency of occurrence in winter, and more so in spring, when they were recorded in nearly 40%o of faeces. In contrast vertebrate occuffence in faeces at 'KB Downs' was much lower, and showed an increase from none in winter to I5o/o in autumn The diet was not significantly different between all sites (R:0.034, p:0.06, dtz), however, the low 'p' value led me to undertake pairwise comparisons between each site. The pairwise results (see Table 5.3) show that FCHQ and 'KB Downs' are significantly different (ANOSIM: R:0.045, p:0.023). The differences in the composition of the diet at these sites, as outlined above, are proportionally the greatest within the food groups consumed less frequently (e.g. earwigs, moths and vertebrates; see Figure 5.4), and it appears likely that these groups accounted for this result. These differences are not considered to be a reflection of major differences in diet between the sites, and probably in part reflect differences between food availability at each site. 5.3.2 Potential prey items collected in micro-pitfall traps Over 20,000 macro-invertebrates from 2l Orders were trapped, sorted and counted from the eight micro-pitfall trap sites established at FCHQ and 'KB Dorilns'. A small number of vertebrates, from two Orders, were also captured. Trapping occuffed between June 1997 and July 1998 and the total trap effort for each site ranged from 315 to 405 trap-nights (Table 5.4). r24 Table 5.3. The results of a comparison between the diets of bush stone-curlews Burhinus grallørius at the three main study sites using the Bray-Curtis test of similarity and an analysis of similarity (ANOSIM). NB: The significance levels in the pairwise tests are not adjusted to allow for multiple comparisons. PAIRWISE TESTS Stat Value Significance Level FCHQ - 'K.El Downs' 0.045 P:0.023 FCHQ - 'Brookland Park' 0.043 P:0.143 'KB Downs' - 'Brookland Park' 0.001 P:0.452 Tabte 5.4. Total trap effort for each micro-pitfall trap site (trap-nights) at Flinders Chase Headquarters and 'KB I)owns' between June 1'997 and July 1998. Site FCHQ 1 FCHQ 2 FCHQ 3 KBl T t25 The average number of captures per micro-pitfall trap-night for all prey groups combined are shown in Figure 5.7. For all but one site (KB4) the capture rates were very similar, with between approximately four and six captures per trap-night. In contrast site KB4 had an ayerùge of over 20 capines per trap-night. The high captures per trap-night at KB4 predominantly resulted from the capture of 5,500 individuals from one species of beetle during summer. This accounted for nearly all of the 6,966 beetles captured in that season, and half of the total number of beetles captured at KB4. This site consisted of semi-improved pasture that had a recent history of super-phosphate being added, which may have accounted for this site supporting such an abundance of this species. This species of beetle was observed on other farms elsewhere on Kangaroo Island (pers' obs'). A Bray-Curtis test of similarity showed that all eight sites were at least 80% alike (Figure 5.8), and all the FCHQ sites were clumped together, and were approximately 85% alike (Figure 5.8). A one-way analysis of similarity showed that all eight sites were not significantly different (R=0.262, p:0.16). Based on this analysis the data for all three sites at FCHQ were combined, as were data for the five sites at 'KB Dotryns'. The capture rates for each prey group collected in micro-pitfall traps at each study site are shown in Figure 5.9. The total average number of captures per trap-night were 4'2 at FCHQ (three sites) and 7.8 at'KB Downs' (five sites). Beetles and ants were by far the most abundant invertebrates captured, accounting for 80% of captures at both study sites, although beetles were more abundant at 'KB Downs' and ants were more abundant at FCHQ. The reason for the high numbers of beetles at 'KB Downs' has been outlined above. The abundance of ants at FCHQ primarily resulted from high numbers of one species lridomyrmex purpurea that was captured over the summer/autumn period. This species is predominantly active during warïner temperatures during the day, and was probably caught on days when the temperature was still quite high when the pits were opened at dusk. These ants may not have been very active later when the birds were foragmg. All other groups accounted for much less than 10"/o of total captures per trap-night with spiders, earwigs and snails having relatively high capture rates at Q and 'KB Downs', and worïns, lawaelcaterpillars and 'others' also featuring at 'KB Downs'. A small number of vertebrates, in particular frogs, were also captured in the micro-pitfall traps. 126 Figure 5.7. Average number of captures per trap-night for each micro-pitfall trap site at Flinders Chase Park Headquarters and 'KB I)o\ryns' between June 1997 and July 1998. 22 20 18 .9 6 tr CL fit l- 14 (ú iI 2 to o 0 f CL oG I (¡, cD G o 6 4 2 I tltll 0 FCFA 1 FCI-|Q2 FCt-lQ 3 KB1 KB2 KB3 KB4 KB5 t27 Figure 5.8. Bray-Curtis similarity dendogram for all micro-pitfall trap sites. Sites sl-s3 are the sites at Flinders Chase Park Headquarters and s4-s8 are the sites at 'KB Downs'. PITTAX s4 s? sl s3 s6 s8 70 80 90 BRAY-CURTIS SIMILARITY r28 Figure 5.9. The captures per trap-night of all prey groups for the micro-pitfall trap sites at Flinders Chase Park Headquarters and 'I(B I)owns'. Data were combined for all three sites at Flinders Chase Park Headquarters and all five sites at'KB Downs'. (4.s) ¡FCHQ g KB Downs' 2.5 2 E .9 tr I (!CL 1.5 (ú Ë o- o o CL oG 05 0 f .*. .""" "-.- *Ñ ss" ".'::"t ."".."."C ""t t29 Figure 5.10 shows the seasonal changes in capture rates for each prey group at FCHQ and 'KB Downs' respectively. As indicated in the methods (Section 5.2.3) the data set were manipulated to ensure that the trap effort for each season was equal. Trends in capture rates were broadly similar for each study site, particularly for beetles, ants, earwigs and snails, which peaked in abundance in summer at both sites. Spider abundance increased to a peak in summer at 'KB Downs', but peaked in spring at FCHQ, with other seasons having approximately equal capture rates. All other groups v/ere captured at such low numbers that seasonal trends in abundance were not as easy to discem. However, the following points summarise the apparent trends in the data: moths appeared to increase in abundance in spring and autumn; wonns were more abundant in winter and spring, especially at 'KB Downs'; lawaelcaterpillars were more abundant in spring, and were not captured at all in autumn; scorpions were only captured in summer; vertebrates \Mere more abundant in winter and spring; and the 'others' group showed a peak in spring at 'KB Do'wns', but no obvious trends at FCHQ. The seasonal trends in abundance that are evident were generally not surprising and showed expected patterns of abundance and/or activity for each group. These seasonal trends will be considered in more detail in the next section. 5.3.3 Comparisons between food groups recorded in faeces and captured in micro- pitfalt traps Of the main groups of animals recorded in micro-pitfall traps all except worrns were also recorded in the faeces of the birds. A small number of 'other' invertebrates (such as crickets, grasshoppers, wasps) that occurred in very small numbers (Figure 5.9) were also not recorded in faeces. Although soft-bodied prey items are less likely to be evident in faeces, worrns were the only members of that group recorded at relatively high capture rates (particularly at 'KB Downs') but were not recorded in faeces. The pattem of occurrence of food items in faeces (Figure 5.4) is broadly similar to the relative abundances of these items in the micro-pitfall traps (Figure 5.9). The birds consumed all of the major prey groups captured in micro-pitfall traps, including small vertebrates. The major food group, beetles, was also the most abundant group captured in micro-pitfall traps. Despite alarge variation in abundance of beetles between the sfudy sites their occuffence in faeces 130 Figure 5.10. Seasonal variation in capture rates of prey groups at (a) Flinders Chase Headquarters and (b)'KB l)owns'. (a) 3 E Et z.c^- 'Ë CL (E Ë2 (ú tr ì/Vnter ä r.s E Spring o I SunrrBr 0, IAuturm =a CL oaú 0.s Fq, E 0 *t a-t ..Y .E *Su {..'o" "** .u"{.o."O (b) 5 4.5 E- '¿4Ð o. ,E s.s =túâ trWnter o- E Spring 2.5 -o I SunrrBr o lAuturm CL I 1,5 tr orúl = 0. 0 ** a"t ."." "E r*u $.*o" .ê' -u'{"o."O 131 was very similar for each site. Ants were also well represented in the faeces, with the higher abundance at FCHQ possibly reflecting the greater abundance of these invertebrates at that site (Figure 5.9). Of all potential prey groups the data suggest that four groups (spiders, moths, centipedes/millipedes and larvaelcaterplllars), were consumed more frequently than their relative abundance would suggest. All of these groups had less than 1.5 captures per trap- night but occurred in between 10-40% of all faeces. Possible reasons for this will be outlined in the discussion. A comparison of seasonal patterns in the diet of the birds (Figure 5.6) at the two sites with seasonal changes in the capture of prey items (Figure 5.10) shows that the consumption of food groups by bush stone-curlews was broadly similar to the seasonal patterns of abundance/activity of these groups. This is evident for beetles, spiders, ants' and lawaelcaterpillars. For those groups that were captured in relatively low numbers such patterns are harder to discem, particularly for moths, centipede/millipedes and vertebrates. Based on my data, the birds clearly have a broad diet that broadly reflected the abundance and/or activity of prey groups. In general terms the birds do not appear to have major preferences for any particular prey group(s) although some groups appear to be consumed at higher rates than their abundance would suggest by chance alone. However, these data must be considered with regards to the potential biases in the sampling methodologies used, and the lack of knowledge on the foraging habits of these birds. The influence of these factors will be discussed below. 5.4 DISCUSSION 5.4.1 Determination of diet using faecal analysis Whilst the use of faecal analysis in the determination of the diet of birds is common practice the limitations of this approach are well known (see Section 5.I.2). Hovrever, in this study faecal analysis was considered to be a very effective method for determining the diet of bush stone-curlews, particularly as faeces were regularly deposited at roost sites, and these could be collected \¡/ithout having any impact on the birds. These sites were revisited and all conspicuous faeces were removed each visit allowing all faeces collected to be assigned to a particular month and season. The opportunistic collection of faeces meant that sample sizes varied between seasons and between each site (Table 5.2). However, sample sizes were t32 adequate for comparing sites and seasons. During the period that micro-pitfall trapping was taking place an effort was made to collect faeces just after each trapping session at each site, although many faeces were also collected at other times. The nature of collecting faeces opportunistically may have contributed towards variation in the recorded composition of diet between sites and between seasons. However, the results showed that the overall composition of the diet varied relatively little, and the same food groups were consumed at each site. Differences between prey availability at each site is also likely to have contributed to these differences and this is discussed in more detail below. 5.4.2 Use of micro-pitfall traps to determine potential prey resources Micro-pitfall data may not reflect abundance of animals, and are really only useful as a relative measure of ground invertebrate activity for making comparisons between sites (Section 5.1.3). Based on the known habits of bush stone-curlews micro-pitfall traps were considered the best method for investigating potential prey resources, which are essentially a function of both abundance and activity of the prey groups' Temporal comparisons are potentially problematic where changes in weather conditions and animal activity can bias results (Melbourne 1999), but these variables were considered to be equal for all sites. Variations in habitat structure can also bias results and comrpt comparisons between sites. Holvever, at each sampling site nine micro-pitfall traps were spread over a relatively large arca (see Figure 5.3) and the data for all nine traps were pooled. There was variation in the numbers of captures between each micro-pitfall trap (pers. obs.) and I assumed that variation in micro-habitat around each trap probably contributed to these differences. The pooling of data for nine traps at each site therefore helped to account for differences resulting from micro-habitat. Despite the potential biases associated with pitfall trapping most pitfall trap sites averaged a very similar number of capture rates per trap-night (Figure 5.7) and the overall captures of different food groups were very similar for each site (Figure 5.8). On this basis the data for each site at FCHQ and at 'KB Downs', were combined and I considered that these data provided a good indication of the relative abundance of different prey groups over time. Importantly, an understanding of the movements and home range sizes of the bush stone- curlews at FCHQ and 'KB Downs', and the mobility of these birds (see Chapter 3), also 133 provided a biologically based justiflrcation for combining the micro-pitfall trap data at each study site. The locations of the micro-pitfall sites, and therefore the areas sampled for potential prey groups, all occurred well within ùn atea that could be searched by a bush stone- curlew within a single night. These birds are quite capable of moving widely over the available foraging habitat in search of prey. 5.4.3 The composition of the diet A wide range of food groups were recorded in the diet of the birds (Figure 5'4), with relatively little seasonal variation (Figures 5.6). This result is consistent with previous studies and anecdotal observations (Marchant and Higgins 1993). All of the food groups recorded in this study have previously been recorded in the diet of bush stone-curlews, which is not surprising given the large number of groups previously recorded in the diet of these birds (see Table 5.1). The frequency of numbers of food groups within individual faeces (Figure 5.5) is also not surprising, and is consistent with the wide variety of food that is consumed' These data alone suggest that bush stone-curlews are opportunistic foragers and take whatever ground-dwelling prey that are available. Although the foraging habits of these birds have not been studied in detail they are thought to glean surface features and probe soft soil (Marchant and Higgins 1993) and the food items recorded in this study clearly supports this. Moths were the only prey group recorded that are not ground dwelling. A detailed study of foraging habits would assist with interpreting dietary data collected from faecal analysis, although this would be logistically quite difficult due to the nocturnal habits of the birds. Beetles occurred a lot more frequently in faeces than all other groups and clearly comprised a major component of the diet regardless of the fact that their hard exoskeletons/mandibles are more likely to pass through the digestive system intact (see section 5.1.2). Spiders, ants and lawaelcaterpillars also contributed significantly to the diet, despite the fact lhat these food groups are likely to be under-represented due to their soft bodies being readily digested (Green and Tyler l9S9). Experiments with stone curlews in England showed that the contribution of spiders based on remnants in faeces was seriously under-estimated (Green and Tyler 1989). Both spiders and lawaelcaterpillars are therefore likely to have contributed more to the diet than indicated in Figure 5.4. t34 A wide variety of other prey groups contributed to the diet, although to a much lesser extent than the groups discussed above. This can generally be related to the relatively low abundance of these groups. With a wide variety of food groups consumed and two to three food groups frequently present within individual faeces the composition of the diet was expected to be similar atthe different study sites. Therefore, surprisingly, detailed analysis did indicate that the diet at FCHQ and 'KB Downs' was significantly different (p:0.023, see Table 5.3). However, I do not believe that this statistical difference reflected any important differences in diet relative to the ecology of the birds. Minor differences are evident in Figure 5.4 and Figure 5.6, although they are primarily greatest among the food groups that contributed least to the overall diet, and the differences in consumption of these food groups were proportionally greater than for the groups that were frequently consumed. Also, some variation in diet between the two study sites is not surprising given differences in prey availability, particularly as the birds appear to take prey opportunistically. Finally, the statistical comparison between sites was based on a relatively small sample of randomly selected faeces from each season for each site, and this random sample may not have adequately reflected the pooled data shown in Figure 5.4. Given that the birds are widespread and abundant across all of Kangaroo Island it would be expected that some differences in diet would occur due to variation in prey availability across the landscape, but the diet is likely to be based around the same food groups. The majority of the seasonal changes in diet appear to reflect the changes in prey activity and/or behaviour, which also supports the idea that bush stone-curlews are opportunists and take what is available (see below). 5.4.4 Potential prey availability compared with diet As discussed above the use of faeces in determining the diet of bush stone-curlews was considered effective, despite known limitations with this technique. Limitations with micro- pitfall traps have also been discussed, however, the method was considered effective for measuring relative abundance of prey, and changes through time. Given the variety of food groups consumed it was therefore not surprising that in many instances the seasonal composition of the diet (see Figure 5.6) was similar to prey availability (Figure 5.10). Although invertebrates ftom 2l Orders were captured only I0 groups were captured in sufficient numbers to be included in Figures 5.9 and 5.10, and several of these were lumped 135 (as outlined in Section 5.2.3). The other 11 groups were combined into the 'Others' category, which accounted for a very small proportion of total captures. No invertebrates from the others category were recorded in faeces, which was not surprising given the low capture rates. However, these invertebrates, which included crickets, grasshoppers, cockroaches, wasps, and slaters, were probably consumed in low numbers. Few remains would have occurred within faeces, and it is possible that they were overlooked due to this. Regardless, the contribution of these items to the diet of the birds was undoubtedly minimal. Earthworms were the only group of invertebrates recorded in reasonable numbers in micro- pitfall traps that were not recorded in faeces, despite the fact that I specifically looked for remains of this group in faeces (see Green and Tyler (1989). Green and Tyler (1989) found that the recovery of earthworm chetae from faeces was low, and that this food group would have been seriously under-estimated based on faecal analysis alone. This suggests that for the periods when earthworms were captured (see Figure 5.10) it is likely that they were also consumed, particularly as they must have been active on the surface to be captured in the micro-pitfall traps. The low recovery of chetae from faeces of stone-curlews that were carefully fed known quantities of invertebrates (Green and Tyler 1989) suggests that worm remains would be especially diff,rcult to observe in faeces collected from wild birds, in which numerous invertebrate remnants, as well as soil and some plant material makes it difficult to locate tiny identif,rable fragments. All other groups of invertebrates that contributed measurably to micro-pitfall captures (see Figure 5.9 and 5.10) were recorded in faeces. Not surprisingly the two groups with the highest capture rates, beetles and ants, were also recorded in a large proportion of faeces. Whilst captures of beetles fluctuated between seasons, they were recorded in approximately equal frequencies in faeces throughout all seasons, with the only exception to this being the relatively low occurrence of beetles in faeces from 'KB Downs' in winter. Whilst the indigestibility of beetle exoskeletons probably contributed to this, the results clearly suggest that the prominence of beetles in the diet is predominantly a reflection of their high abundance, although obviously the birds must also consider them to be a valuable food source. In comparison there was considerable seasonal variation in the consumption of ants. However, this is not surprising given that ants are generally more active in warmer weather, (Figure 5.10) and the consumption of ants by bush stone-curlews broadly reflected this pattern of availability. 136 The seasonal pattern of consumption of spiders quite closely matched the seasonal pattem of capture rates, particularly at FCHQ, which supports the apparent opportunistic nature of the birds foraging. Captures of moths, lawaelcaterpillars and centipedes/millipedes were generally too low to determine if an increased prominence in the diet equated with an increase in capture rates. Spiders, larvaelcaterpillars, moths and centipedes/millipedes appeared to be more prominent in faeces than captures in micro-pitfall would suggest. This can in part be interpreted in terms of the trappability of these groups. Micro-pitfall traps were not likely to adequately sample the abundance of moths. Centipedes and millipedes may also be less likely to stumble into micro-pitfalls due to their relatively long body plans, allowing them to 'retreat' even after partially entering the micro-pitfall trap. The use of micro-pitfalls to sample spiders is also known to have limitations (see Topping and Sunderland 1992, Topping t993). Also larvae and caterpillars may be poorly sampled with micro-pitfalls as they are relatively immobile, and caterpillars in particular are likely to remain feeding on the same plant for considerable lengths of time. The other altemative explanation for the apparent prominence of some food groups is that they are actively sought out by the birds. Spiders and larvaelcaterpillars would generally provide large meals compared to many other food groups, including beetles and ants (pers. obs. of micro-pitfall captures), and would be relatively easily digested. Centipedes would also provide relatively large meals þers. obs.). Further research would be required to demonstrate if bush stone-curlews had clear preferences for certain invertebrate groups. The remaining invertebrate food groups (earwigs, snails and scorpions) were also consumed, and captured, in relatively low numbers and therefore seasonal comparisons between consumption and capture rates are difficult. Based on the results for the groups discussed above, it is likely that the consumption of these groups was higher when they were more abundant. Snails appear to show the only major diversion from this generalisation. There appeared to be a switch to consuming a lot more snails in autumn (an increase from less than l0o/oto over 40Yo at FCHQ, and from -10% to over 65Yo at 'KB Downs'), although capture of snails in pitfall traps peaked in summer at both sites. Capture rates for beetles and ants were relatively low in autumn, however, both remained prominent in the diet. Spiders were also captured at relatively low rates in autumn, although consumption of this food group was only relatively low at FCHQ. It is therefore difficult to account for the major increase in r37 consumption of snails in autumn, although these data possibly suggest that autumn is a period of food shortage. Whilst beetles continued to occur in over 90o/o of faeces during this period despite their relatively low abundance, this may in part be a function of their hard exoskeletons remaining in the digestive track for longer periods. The increase in consumption in snails may therefore reflect a decrease in abundance of other food groups, requiring the birds to seek extra prey groups. The consumption of vertebrates by bush stone-curlews has been documented previously. All but one of the vertebrates captured in micro-pitfall traps were frogs. Although the traps were smaller than the pitfall traps generally used to catch vertebrates, including frogs, the capture of a range of species of different sized frogs suggested that they were adequate for sampling this group. These animals were quite abundant at both study sites, especially during winter and spring. It is therefore not surprising that their contribution to the diet was considerable, especially at FCHQ. The lower occuffence at 'KB Downs' is unaccountable. The benefits of consuming individuals from this food group (larger body sizes) are likely to be considerable compared to all other food groups. It is therefore not surprising that frequency of vertebrates in faeces appears to be relatively high compared to capture rates in micro-pitfalls. These food items are probably highly sought after. 5.4.5 Conclusions The diet of bush stone-curlews on Kangaroo Island is similar to that reported elsewhere. The diet is broad with many groups of invertebrates, and vertebrates, being consumed. Combined with the fact that similarities between the diet of the birds and abundance and./or activity of prey groups occurred, this confirms that the birds are opportunistic foragers and generalists with regards to diet. The high capture rates of ground-dwelling invertebrates in pitfalls at all times of the year would suggest that bush stone-curle\Ms are unlikely to be limited by prey resources within most agricultural landscapes. This provides further circumstantial evidence for the significant impact that foxes appear to have had on populations of these birds across southem Australia, where relatively similar habitat exists. 138 CHAPTER 6 MANAGEMENT OF BUSH STONE.CURLEWS ON KANGAROO ISLAND AI{D THE MAINLAND OF SOUTH AUSTRALIA 6.1 INTRODUCTION The purpose of this chapter is to discuss the management of bush stone-curlews on Kangaroo Island, with reference to mainland South Australia, and to make conservation management recommendations. The information outlined in the previous chapters provides an insight into the ecology of bush stone-curlews on Kangaroo Island. However, this study is only the first step towards understanding the ecology of bush stone-curlews on Kangaroo Island. The information provides a basis from which to suggest management strategies. These strategies are aimed at ensuring the population remains viable on Kangaroo Island, and the situation on the mainland improves. 6.2 STATUS OF BUSH STONE-CURLEWS The status of bush stone-curlews in South Australia was recently down-graded from endangered to vulnerable (NPW Act; 2000 revision of Scheduled species), primarily as ù result of this study, which showed that the birds were widespread and abundant across Kangaroo Island (see Chapter 2). Chapter 2 highlighted the marked decline in the range of the birds since European settlement on the mainland, and confirmed that the birds only persisted in relatively few areas there. Forhrnately the situation on Kangaroo Island is different and agricultural development has created habitat for these birds (see Chapter 3 and 4). Therefore Kangaroo Island is the only major stronghold for this species in southern Australia, and as such this population of bush stone-curlews is very important. Estimating the population size of bush stone-curlews on Kangaroo Island is fraught with difficulties, however, such an estimate helps to define the status of the birds more precisely' Estimates of population size can be made using range sizes of breeding birds, estimating the area of potential habitat on the island, and by making a few assumptions. These assumptions were as follows: 139 1. Potential available habitat was -318,000 ha. This was calculated as the total area of the island (-460,000 ha) less all large areas of intact native vegetation since these do not provide suitable foraging habitat for the birds (i.e. no NPWSA reseryes were included in potential habitat). 2. Average home range size for a breeding pair was assumed to be 100 ha (slightly more than the overall average for breeding pairs measured in this study, which was -90 ha). It is likely that densities of breeding pairs reduce towards the east end of the Island where vegetation remnants (i.e. roost sites) are fewer and smaller. 3. Breeding pairs do not have overlapping home ranges. 4. 20 to 50o/o of potential habitat on Kangaroo Island is actually suitable for breeding. 5. 20o/o of the population is made up of non-breeding birds. Based on these assumptions the population estimate for the Island ranges from 1,590 birds (i.e. 1,272 breeding birds plus 318 non-breeding birds) to 3,975 (i.e. 3,180 breeding birds plus 795 non-breeding birds). These estimates are speculative, and are particularly dependent on the estimates of the proportion of available habitat that is suitable for breeding pairs (see Chapter 3). Although on the western end of Kangaroo Island this proportion would appear to be quite high þossibly higher than 50Yo) when considering the whole Island this is more likely to be the upper limit (based on pers. obs.). 6.3 THREATS TO BUSH STONE.CURLE\MS 6.3.1 The role of predation by foxes and habitat modification The major threats to bush stone-curlews on the mainland are considered to be predation by foxes and loss of habitat (Marchant and Higgins 1993). Many ornithologists from early in the last century made anecdotal observations suggesting that the decline of bush stone-curlews in their districts coincided with the arrival and establishment of foxes (see Chapter 2). In many areas these observations rwere noted before the majority of broadscale clearance of vegetation had taken place. Based on my research the evidence supports these observations that predation by foxes is by far the greatest threat to these birds. It is likely that foxes are able to capture adults, as well as taking eggs and chicks. The abundance of bush stone-curlews on Kangaroo Island, where foxes are absent, provides strong evidence in support of the impact of predation by these introduced animals. There are also two other pertinent factors which support this. First, the preferred habitat of bush stone- curlews (open grassy woodlands, see Marchant and Higgins 1993), were unlikely to be 140 present on the Island until recent times and most of the natural vegetation was probably quite dense, as it is today. Clearly, the development of Kangaroo Island for agriculture actually created habitat for these birds, which now rely on cleared land for foraging (see Chapter 3 and 4). The resultant loss of habitat for most other species of birds (and other faunal groups) was therefore beneficial to bush stone-curlews. The general agricultural landscape on the Island is not very different from many areas on the mainland, which would also appear suitable for the birds, although they are now absent across most of these areas. The fact that the birds appeat to be relatively abundant in northem Australia, where foxes are also absent, supports this notion. The second factor supporting the notion that predation by foxes is the major threatening process for bush stone-curlews is that the birds have also disappeared from much of the arid zone of South Australia (see Chapter 2). Obviously habitat change has occurred in this zone (e.g. as a result of altered fire regimes and grazing by stock and feral animals) but these changes would not appear to be as dramatic as in the temperate zone where wholesale clearance of habitats has occurred. These observations also suggest modifications to the natural habitat of these birds were probably not the major driving force behind their decline, and that predation by foxes was probably a greater problem. Finally, all bush stone-curlews clearly need some remnant vegetation for shelter during the day. Numerous remnants of varying sizes are present throughout the agricultural landscape on Kangaroo Island, providing a mosaic of suitable habitat for the birds (see Chapter 3 and 4). The quality and size of the remnants used by the birds does not have to be great (see Johnson and Baker-Gabb 1993, and Chapter 4), and therefore in all but the most over-cleared agricultural landscapes, suitable remnants for the birds to shelter in are likely to be present. Despite this the birds have become extínct throughout most of their former range on the mainland. Whilst foxes appear to be the major problem for these birds, habitat loss and modification would have contributed to the demise of the birds in some regions. Although the birds will use small remnants of native vegetation of poor condition, such remnants are likely to be subjected to more frequent disturbances, including incursions by predators, livestock, and humans and their pets/work animals. t4t 6.3.2 Ongoing changes to preferred habitat in Kangaroo Island Current and impending changes to foraging habitat are occutring on Kangaroo Island and these may have a detrimental effect on the birds (see Chapters 4 and 5). Both short and long- term land-use changes are occurring as farmers respond to depressed markets for traditional products like wool and seek altemative sources of income. In particular the amount of annual cropping has increasing substantially on the island (see Figure 6.1) and the total tonnage of all crop production has quadrupled from -5,800 t to greater than 20,0001 since 1994195 (Figure 6.1). This has resulted from a major increase in the amount of barley and oats sowed, as well as the introduction of new crops such as canola and triticale. This increase in production is reflected in a commensurate increase in the area being cropped. Annual land-use changes such as these are likely to result in short-term changes to prey groups, through an increase in theuse of pesticides andherbicides, as well as direct alteration of the structure of the foraging habitat itself (see Chapters 4 and 5). Increased use of chemicals may also result in an increased uptake of chemicals by the birds. The overall impacts of short-term loss of foraging habitat are uncertain, although the birds can probably adjust to these changes. The longer- term effects of increased uptake of environmental contaminants is possibly of greater concern. However, the effects of this are unknown. Forhrnately the total area under crops is likely to have reached its peak (4. Ewers, Industry Development Officer, Primary Industries and Resources, South Australia; pers. comm.). However, innovations in cropping technology could see this situation change in the future. Of greater concem are longer-term changes associated with activities such as forestry. This activity will lead to long-term changes to foraging habitat,leaving large areas unsuitable for ten or more years. A relatively large area of western Kangaroo Island is being converted to forestry (Figure 6.2). Itremains to be seen what impact this will have on bush stone-curlews, although with foraging habitat reduced considerably, and therefore potential breeding territories reduced, it is reasonable to assume that the area will support less birds. The westem end of the Island appears to provide better habitat than the eastem end for bush stone- curlews, thereby increasing the relative impact of forestry activities. 6.3.3 Other threats On Kangaroo Island there appear to be few other major threats to bush stone-curlews, and the abundance of adults and juveniles, and chicks and fledglings observed, particularly on the westem end of the Island (pers. obs.) supports this. Feral cats, Corvus species and grey r42 Figure 6.1. Trends in crop production on Kangaroo Island, 1987/88 -2OOllO2. The graph shows the production of the four major crops on Kangaroo Island in tonnes, along with totat production, and the total area cropped (in nect¿ìes). Area data were only available since 1Þ97198- Crop data for 1998199 were unavailable. Data for 2001102 were predicted based on seasonal conditions and communicatiois with farmers (Shaun Capper, South Australian Cooperative Bulk Handling, pers. comm.) Total production is very dependent on seasons, and the major reduction in 2000/01 reflects poor se¿Nons. Whilst the apparent trend is towards an increased area being cropped, based on the available arable landon the island, this figrre is expected to remain between 23,000 ha and 30,000 ha into the foreseeable future (Andrew Elvers, Primary Indisutries and Resources South Australia, pers. comm.). 20000 40000 18000 35000 (ú r6000 Ê 30000 tr f! o o 14000 Wheat o 25000 It tt 12000 Ê Barley o tú '-r o. Oats CL 10000 20000 tr e o Canola o o -+Total (ú 8000 15000 It= It e +Area 6000 o. t r0000 E c o ¿1000 t- 5000 æ00 0 0 87/88 88/89 89/90 90/91 91/92 92t93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 WlOl 01102 143 Figure 6.2. Existing and Proposed Agro-Forestry Plantations on Kangaroo Island. .: .. :, I I Forestry (all) I NPWSA Reserves 0 5 10 Kilometers A Native Vegetation r--___-] N t44 cuffarwongs Strepera versicolor, brush-tailed possums Trichosurus vulpecula anð heath goannas Varanus rosenbergi are the only large predators on the island. Heath goannas are only active during the warmer period of the year, and during the day, and due to their size and foraging habits they would not pose any serious threat to adult birds. However, goannas may occasionally disturb nesting birds and would readily consume eggs. This is not considered a major threat. The brush-tailed possum Trichosurus vulpecula will occasionally take eggs of the birds (pers. obs.), as it typically forages on the ground on Kangaroo Island. Corvus species and grey curïawongs may also take eggs, although the adult bush stone-curlews would probably be able to provide protection for small chicks. These birds were always observed in the vicinity of bush stone-curlew nests, although the secretive habits of the birds may have helped ensure that eggs remained undetected. The potential for predation from these natural predators is considered to pose only a very minor threat to the birds. Feral cats are likely to pose a more serious threat as they would be capable of taking young birds, from hatchlings to fledglings, and may attempt to kill adults. Currently feral cats occur across the whole island, but they appear to be more abundant in the more disturbed areas of the eastern end of the island (pers. obs.). It is diff,rcult to say what impact cats might be having, although currently they do not appear to be having a major impact on the birds. Studies on breeding success across the island, with varying densities of cats, would provide a useful indicator of the impact that cats, and other predators, may be having. Given that cats have been present in reasonable numbers for years, and bush stone-curlews are widespread and abundant, cats do not appear to be a great threat at present. 6.3 RECOMMENDATIONS FOR FURTHER RESEARCH AND MANAGEMENT The following recommendations aim to address the conservation management of bush stone- curlews both on Kangaroo Island, and on the mainland of South Australia. The recommendations for Kangaroo Island predominantly comprise research and monitoring actions as currently known threats do not appear to be having a major effect on the birds. Recommendations for the mainland primarily relate to specific conservation strategies, some of which are already being planned, or implemented, with the assistance of the knowledge gained from this study. 145 6.3.1 Recommendations for Kangaroo Island 1. Monitoring of the population Use the methods outlined in Chapter 2 to monitor the population by repeating the call- playback surveys across the island. This will provide general information on changes to the distribution of the birds. This broad-scale monitoring should occur every five years. Fine-scale monitoring is recommended if a decline in the population is detected. This could take the form of spotlight transects at several locations across the island. Variation resulting from differing weather conditions would have to be accounted for, with repeated sampling over several nights required to determine variance. Spotlight counts such as these would also allow the number of chicks or juveniles to be counted between spring and autumn, which is an important indicator of the health of the population. This detailed monitoring, if required, would need to occur at least annually. 2. Assessing the impacts of land-use changes on the birds As discussed above, short and long-term changes to the habitat of the birds, especially foraging habitat, may have a detrimental impact on the birds. Ideally the impacts of such changes on the birds should be measured and monitored to determine potential long-term effects, and to identify management practices that can help to ameliorate these impacts. It is recognised that a project such as this would require a reasonable level of resources. However, the impacts of activities such as forestry on the biodiversity of Kangaroo Island should be monitored as a matter of course. This could occur in conjunction with monitoring of macropods, which is being undertaken by NPV/SA to assess their abundance and the effects of various control methods within the forestry plantations' It is estimated that -22,000 ha of existing pasture will be converted to forestry. This as forestry is represents -5%o of the potential habitat across the whole island. However, predominantly occurring in the wetter areas on western Kangaroo Island, which also appears to support a higher density of bush stone-curlews þers. obs.), the impact may be more pronounced. To determine the potential threat of this land-use change the distribution and abundance ofthe birds should be assessed in areas that have been selected for forestry prior to planting, and at regular intervals as the trees grow and mature. t46 3. Investigating breeding success across Kangaroo Island. Breeding success is a much more useful measure than presence alone when considering the status of the birds, and identifying potential threats. Breeding success at locations with high and low percentages of remnant vegetation, and different land-uses should be compared (i.e. west versus east Kangaroo Island). Although time consuming, it would not be particularly difficult to monitor the fate of nests and chicks. This would be suitable as a post-graduate research project. 4. Quantifying foraging habits and time budgets. This information would provide a much better indication of how the birds acfially use the habitat within their home ranges. Although logistically difficult, with good night vision equipment this would be feasible. A study of this nature would also be suitable for a post- graduate research project. This could be undertaken at different sites across Kangaroo Island to compare the effects of various land-uses. 6.3.2 Recommendations for the South Australian mainland 1. Monitor all known populations Monitoring programs have been established at the two main populations that persist on the mainland using the call-playback methodology developed in this study. In 1996 surveys Ìvere initiated at Bookmark Biosphere Reserve in the Riverland and in 1999 surveys were initiated in Lincoln National Park adjacent to Port Lincoln (see Gates 1999). Monitoring of other populations may be diffrcult due to low numbers of birds, however, it is important to know if these populations persist, and to implement fox control programs if necessary. These programs should continue indefinitely whilst the populations are very small. At Lincoln National Park, and the nearby Coffin Bay National Park, monitoring of bush stone-curlews has a dual role. As predation by foxes is the major threat to the birds on the mainland, they have been identified as a good indicator of the success of fox baiting programs. As part of the 'Ark on Eyre' project (see Cotsell 2000) large areas within these parks are being baited to control foxes. A monitoring program for the birds has been established to determine if they respond positively to the baiting, either by occupying new areas of suitable habitat, and/or by breeding successfully (see Gates 1999). This monitoring program not only tracks the status of the bush stone-curlew population, but it also provides an important performance indicator for the success of the fox baiting program. r47 2. Control foxes at small isolated populations Foxes are clearly the major threat to bush stone-curlews. A few small and isolated populations of the birds have persisted at several sites within South Australia, often because natural features such as islands provide refuge. The control of foxes in the vicinity of such populations should increase recruitment rates, and thereby increase the chances of the population surviving in the long-term. Any fox control should only occur as part of a well- designed and ongoing program, and monitoring of the outcomes needs to be an essential component of any such programs. 3. Re-introduce bush stone-curlews into predator free areas within their former range Although not considered a high priority the re-introduction of bush stone-curlews into parts of their former range is a feasible conservation management option. Several restoration/recovery projects have been initiated in South Australia in recent years including 'Operation Bounceback' in the Flinders Ranges (see Depreu 2000), and the 'Ark on Eyre' project (see Cotsell 2000) which includes the maintenance of a predator free zone within Venus Bay Conservation Park. The aim of these projects is to retum species such as bush stone-curlews and medium sized mammals, including bilbies Macrotis lagotis and burrowing bettongs Bettongia lesueur, to areas of their former range. My study on Kangaroo Island highlights the island as a suitable source for wild birds for such projects and provides the background necessary for the development of translocation plans for bush stone-curlews. A trial reintroduction into Venus Bay Conservation Park occurred in July 2001 (Cotsell 2001) 6.4 CONCLUSIONS My study has confirmed the importance of Kangaroo Island as a refuge for bush stone- curlews in southem Australia, and has provided information that will assist with the management of the species, both on Kangaroo Island and on the mainland of South Australia. Indeed some of the information derived form this study is already contributing to conservation programs for the species on the mainland (see Gates 1999, Cotsell 2000). While no major threats to the island population are apparent, particularly with the absence of foxes, this does not justify a sense of complacency. Many apparently common species of birds are currently undergoing major declines on the mainland of South Australia, where habitat clearance occurred much earlier than on Kangaroo Island, and was also more severe. The effects of habitat loss are currently less obvious on Kangaroo Island, although it is 148 probable that it will simply take longer for the effects to show. The decline in woodland dependent birds in particular (see Robinson and Traill 1996) is likely to occur on the island, just as it has in the nearby Mt. Lofty Ranges (Paton et al. 1999). This decline probably in part reflects a decline in invertebrate abundance. Whilst bush stone-curlews forage in cleared areas, the effects of a reduction in the total abundance of invertebrates across the landscape may be detrimental. Fortunately for bush stone-curlews they are reliant on the cleared land. However, as discussed, changes to land-use pattems on the island are occulring and the potential impact of these on bush stone-curlews, either directly or indirectly, is of concern' The complex interactions inherent in ecosystem decay (e.g. Hobbs and Hopkins 1990, Morton 1990) and their impacts on species are still being determined. 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Ecology 70, 164-68. 161 APPENDIX 1 PAST RECORDS OF BUSH STONE-CURLEWS IN SOUTH AUSTRALIA. All positions are in decimal degrees Pre 1940 LOCA YEAR DAY MONTH (Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER I 840 I I Adelaide 138.58 -34.92 RAOU Atlas Data-base 1852 1 I Wonga 139.50 -34.00 RAOU Atlas Data-base I 863 t2 6 Lobethal t38.92 -34.92 RAOU Atlas Data-base 2< aî I 867 10 2 Mclaren Vale 138.55 RAOU Atlas Data-base r867 t'7 2 Edwardstown t38.62 -35.05 RAOU Atlas Data-base I 880 1 I Grange 138.50 -34.93 RAOU Atlas Data-base I 887 I I Mount Gawler 138.75 -34.75 RAOU Atlas Data-base 1887 1 9 Rostrevor 138.63 -34.88 RAOU Atlas Data-base 1 888 I 1 Glenelg 138.51 -34.95 RAOU Atlas Data-base I 890 1 I Adelaide 13 8.60 -34.93 RAOU Atlas Data-base I 890 I I Adelaide 138.66 -34.93 SA White Collection 1897 I 7 Namrng t39.17 -35.51 SA White Egg Collection 189'7 I '7 Poltalloch 139.25 -35.57 RAOU Atlas Data-base t897 25 9 Rockleigh I 39.10 -34.90 RAOU Atlas Data-base I 898 I I Tea Tree Gully t38.74 -34.79 RAOU Atlas Data-base I 899 I 8 Mt Lofty 138.71 -34.98 SA White Egg Collection 1 899 1 8 Summertown r38.72 -34.98 RAOU Atlas Data-base 1900 I I Hindmarsh Valley 138.s0 -3s.50 RAOU Atlas Data-base 1901 I I The Gums 139.35 -33.85 RAOU Atlas Data-base 1901 I I Adelaide 13 8.58 -34.94 RAOU Atlas Data-base ,l l90l l9 8 t32.50 -27.50 RAOU Atlas Data-base t 901 I t2 2 137.00 -27.00 RAOU Atlas Data-base 1905 1 1 Parabarana Hill 139.83 -30.00 RAOU Atlas Data-base l 90s 1 I Mount Gawler I 38.82 -34.75 RAOU Atlas Data-base I 905 I 10 Pioneer Bend 137.30 -35.75 RAOU Atlas Data-base 1905 10 5 Fulham 13 8.51 -34.93 SA White Egg Collection 1905 5 10 Grange I 38.50 -34.92 RAOU Atlas Data-base l 906 5 9 Fulham 138.51 -34.93 SA White Egg Collection 1906 5 9 Grange l3 8.51 -34.93 RAOU Atlas Data-base 1908 7 9 Finniss 138.83 -35.40 RAOU Atlas Data-base I 909 1 l0 Port Douglas 135.30 -34.53 RAOU Atlas Data-base 1909 5 10 Wanilla 135.67 -34.53 RAOU Atlas Data-base 1911 t4 4 Stansbury t37.79 -34.92 RÀOU Atlas Data-base 191 1 l5 4 Curramulka 137.75 -34.75 RAOU Atlas Data-base 191 I I 8 Port Germein 138.02 -33.02 RAOU Atlas Data-base 191 I I 8 Edillilie 13s.70 -34-47 RAOU Atlas Data-base 191 I 24 8 Edillilie 135.68 -34.47 RAOU Atlas Data-base 1911 3 9 Edillilie t35.67 -34.47 RAOU Atlas Data-base l9l I J 10 Kootaberra Outstation 137.50 -32.00 RAOU Atlas Data-base 1912 I 6 Fulham 138.5 I -34.9f SA White Collection t62 LOCAI'ION YEÄR DAY MONTH (NearestNamed Place) LATITUDE LONGITUDE SOURCE OBSERVER Morgan t912 1 8 Kallioota t43.91 -3 1.83 SA om 1(4) 11-21 t9t2 1 6 Glenelg 138.53 -34.94 RAOU Atlas Data-base t9t2 I 8 Kallioota 137.90 -3 1.83 RAOU Atlas Data-base 19t3 I 9 Peebinga r40.92 -34-92 RAOU Atlas Data-base t914 1 I Adelaide 138.61 -34.91 RAOU Atlas Data-base 1915 I I Adelaide parklands 138.60 -34.93 SA Orn 11(3) 64-68. 1915 9 l0 Moolooloo 138.58 -30.98 RAOU Atlas Data-base 1916 I I Wedge Island t36.46 -35.16 SA Om 2(6) 141-lsl Morgan ,) t916 1 I 136.47 -35. I s RAOU Atlas Data-base ,) 19t6 6 I t36.45 -3 5.16 RAOU Atlas Data-base t9t7 I I Near Renmark 140.74 -34.r7 SA Om 3(4) 99-108 Morgan 1917 1 4 Renmark 140.75 -34.t7 RAOU Atlas Data-base 1918 I 10 Hundred ofBookpumong 140.58 -34-35 SA om 4(2) 39-46 Mellor ,l l9r8 I 3 139.92 -29.92 RAOU Atlas Data-base Data-base l9l8 1 10 Noora 140.92 -34.42 RAOU Atlas McGilp 1919 1 1 Moolawatana Station t39.73 -29.91 SA om 4(3) 70-73 t9t9 I 7 Adelaide 138.55 -34.91 RAOU Atlas Data-base 1920 I I Peep Hill 139.11 -34.13 RAOU Atlas Data-base r920 1 6 Edwardstown r38.62 -35.02 RAOU Atlas Data-base 1920 24 6 Blackwood 140.65 -37.93 SA Orn 5(4) 95-97 Ashby 192r I I Clayton 138.90 -3 5.53 RAOU Atlas Data-base t92l I I Waiçinga 138.48 -35.53 RAOU Atlas Data-base t92t r3 7 Mount Emery 135.44 -26.54 RAOU Atlas Data-base Data-base t922 1 3 Port Victoria 137.50 -34.50 RAOU Atlas t922 l3 5 Mount Emery t35.44 -26.54 RAOU Atlas Data-base 1922 6 t2 Kybybolite r40.92 -36.8'7 SA om 7(2) s1-61 Sutton r922 I 8 Ooldea Hill t3t.92 -30.42 RAOU Atlas Data-base 1922 1 t2 Magpie Comer 140.78 -37.25 RAOU Atlas Data-base t922 I T2 Kybybolite t40.96 -36.87 RAOU Atlas Data-base 1923 I I Edwardstown t38.62 -34.97 RAOU Atlas Data-base 1923 2 1 Netherby 136.57 -33.22 SA om 7(2) 62-6s Sutton 1923 6 8 Eureka Bluff 135.50 -32.50 RAOU Atlas Data-base 1923 6 8 Nonning 136.50 -32.50 RAOU Atlas Data-base t923 6 8 Wangary 13 5.50 -34.50 RAOU Atlas Data-base t923 10 8 Coralbignie Outstation 136.35 -32.6',2 RAOU Atlas Data-base 1923 15 8 Smith Bay t37.45 -35.62 RAOU Atlas Data-base t923 t7 8 Eureka Bluff 135.50 -32.43 RAOU Atlas Data-base 1923 20 8 Ilkina Hill r 34.98 -32.33 RAOU Atlas Data-base 1923 1 l2 Edwardstown 138.63 -34.97 RAOU Atlas Data-base Collect. t923 8 15 Wisanger t37.45 -35.62 Museum FE Parsons I Sutton t924 1 I Coralbingie 135.03 -32.28 SA om 7(5) l8-158 r924 I I Wangary 135.48 -34.55 SA Om 7(s) 118-158 Sutton 172-83 Cleland 1924 1 1 Encounter Bay District l3 8.60 -35.58 SA Om 7(6) r924 I I Cosy Comer t19.70 -34.05 RAOU Atlas Data-base 1924 I 1 Grange 13 8.53 -34.93 RAOU Atlas Data-base 163 LOCATION YEÄR DAY MONTH (NearestNamed Place) LATITUDE LONGITUDE SOURCE OBSERVER ,l t924 I 6 140.00 -27.00 RAOU Atlas Data-base 1924 7 7 'Wetunga' 140.63 -f7.s7 SA om 8(l) 29-31 'ùr'hite ,) t924 I 10 139.50 -26.50 RAOU Atlas Data-base t924 7 20 Netherby t36.5'7 -33.22 SA Om 8(1) 32-36 Sutton 32-36 1925 1 I Minnie Downs Via Marree 138.06 -29.64 SA Om 8(l) t925 I 1 White Well (l3mls N Kimba) 136.42 -33.t4 SA Om 8(6) t7l-2r8 t925 I I Mt Charlotte, Hilltown 13 8.64 -33.69 SA Om 8(7) 280-87 Sheckleton 1925 I I The Firs', Ambleside (Brìdgewater) 138.8 t -3 s.0 I SA om 8(8) 33a-47 Heyson Data-base 1925 I 1 Eagle Bore Homeland 132.00 -26.00 RAOU Atlas 1925 2 2 Moolawatana Station t39.73 -29.91 Museum McGilp t925 23 9 Moseley Nobs 136.48 -32.93 RAOU Atlas Data-base 1925 25 9 Rockwater Hill 136.50 -f2.65 RAOU Atlas Data-base 'Weednanna 1925 25 9 Hill 136.47 -32.82 RAOU Atlas Data-base t925 I t2 Point Bonney 138.58 -31.58 RAOU Atlas Data-base 'Wilpena 1925 t2 25 Pound 138.57 -31.56 SA om 8(7) 280-87 Pearce 29-32 Newell t926 1 1 Hindmarsh Island 138.86 -35.52 SA Om 9(l) 1926 I I Wilmington l 38. l0 -32.65 RAOU Atlas Data-base 1926 I I Mount Gregory 138.58 -33.58 RAOU Atlas Data-base t926 I l0 Cobdogla 140.40 -34.25 SAom 9(5) 170-72 Tubbs 1926 I 6 Mylor 138.75 -3 5.08 RAOU Atlas Data-base Sutton t926 17 5 Netherby t36.57 -33.22 SA om 9(3) t927 I I Mount Alexander l3 5.58 -27.08 RAOU Atlas Data-base t92l I 3 Adelaide 138.60 -34.89 RAOU Atlas Data-base 1928 t I Edwardstown 138.62 -34.98 RAOU Atlas Data-base 1928 I 6 Sutherlands / Mt Mary Distrìcts t39.22 -34.16 SA om (1928) Boehm Sutton I 928 I 9 Swan Reach 139.60 -34.57 SA Om l0(1) 22-4s Florieton Dìstrict, The Gums r929 I I Station 139.41 -33.61 SA Orn 10(4) 135-38 Pearse Morgan I 930 I I Moolawatana Station t33;73 -29.91 SA om ll(2) 53-61 Simpson 1930 I 1 64mls S Oodnadatta 135.45 -27.5s SAom l1(3)70-73 1930 I I Bower t39.33 -34-r3 RAOU Atlas Data-base 1930 30 l1 Struan 140.73 -37.13 RAOU Atlas Data-base Sutton 1931 I I Joanna (near Bool Lagoon) 140.86 -f6.20 SAOm 1l(3)74-92 193 I I I Wilmington I 38.17 -32.58 RAOU Atlas Data-base Atlas Data-base 1931 I 1 Mount Tinline 13 8.5 8 -33.75 RAOU 193 I I I Lowbank 140.08 -34. 18 RAOU Atlas Data-base 1931 I I Langhome Creek 139.03 -35.30 RAOU Atlas Data-base 193 I 7 I Edwardstown 138.59 -34.99 RAOU Atlas Data-base 1931 8 I Moolawatana Station r39.7s -29.92 RAOU Atlas Data-base 193 I 24 4 Edward Creek 135.78 -28.27 RAOU Atlas Data-base ,l Atlas Data-base 1931 1 t2 r39.70 -26.49 RAOU t932 I I Near Tarcoola t34.61 -30.78 SAom 11(6) 160-ó2 McGilp r932 I I Micham t38.62 -34.98 SAom 11(7)203 Sutton t932 I I Happy Valley Resewoir t38.79 -35.08 SA om l1(6) 164-6s Pearce 1932 2l I Edwardstown 138.58 -34.9'7 RAOU Atlas Data-base t932 23 3 Tarcoola t34.s7 -30.72 RAOU Atlas Data-base t64 LOCATION \aEAR DAY MONTH (Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER r932 I 4 Blewitt Springs 13 8.5 8 -35.08 RAOU Atlas Data-base 1932 I 8 Mount Heame 134.85 -26.t3 RAOU Atlas Data-base 1932 1 8 Mount Byilcaoora 133.42 -27.25 RAOU Atlas Data-base Simpson t933 1 I Indulkana r33.31 -26.97 SA Om 12(l) 33-36 1933 I I 6mls upstream of Waikerie 140.95 -34.r9 SA Om l2(3) 8s-92 Russ t933 I 1 Langhome Creek 139.08 -35.25 RAOU Atlas Data-base 1933 I 8 Saddleworth 138.78 -34.08 RAOU Atlas Data-base l 933 4 9 Edwardstown t38.64 -34.99 RAOU Atlas Data-base t934 l0 I Bool Lagoon District t40.73 -37.14 SA om l3(4) 107-19 Hood t934 l8 l0 Struan t40.75 -37.08 RAOU Atlas Data-base Smith r 935 I I Chowilla Station 140.84 -34.03 SA om l3(1) 42-47 Atlas Data-base I 93s 1 1 Westem Cove (KI) 137.58 -3s't5 RAOU 1935 I J Bower t39.33 -34.17 RAOU Atlas Data-base 228-30 Brandon 1936 1 I Wilmington District l 38.10 -32.6s SA Om 13(8) 1936 12 I 4mls E Morgan 139.66 -34.03 SA om l4(2) 41-44 Brummitt 1936 I 8 False Cape r 3 8.00 -3 5.83 RAOU Atlas Data-base 1936 I 9 Antechamber Bay (KI) 138.07 -35.80 RAOU Atlas Data-base 1936 1l l0 Sutherlands / Mt Mary Districts 139.35 -34.13 SA Orn 14 (4)91-96 Boehm 1936 I ll Middleback 131.42 -32.92 RAOU Atlas Data-base r936 l0 1l Bower 139.35 -34.13 RAOU Atlas Data-base 1936 t2 11 Reevesby Island 136.36 -34.54 RAOU Atlas Data-base Condon, H.T 1936 18 1l Hurst Plain 139.69 -34.12 RAOU Atlas Data-base ,) t936 4 t2 136.28 -34.53 RAOU Atlas Data-base ,| 1936 11 12 136.28 -34.53 RAOU Atlas Data-base 1936 20 6 Langhome's Creek 139.03 -35.30 SA Om l4(1) 29-34 Brandon t937 I I Glenelg 138.57 -35.07 RAOU Atlas Data-base Data-base t937 1 1 Cape Jervis 1 38. l0 -3 5.60 RAOU Atlas 68-72 Symon t937 1 4 Delamere. 138.20 -35.57 SAom ls(s) 1937 26 3 Penneshaw (KI) t37.94 -3s 78 RAOU Atlas Data-base Pearce t937 8 4 Happy Valley Reservoir t38.79 -35.08 SA Om l4(5) 129 1937 I 9 Malpas 140.58 -34.75 RAOU Atlas Data-base Florieton District, The Gums 14(6) 163-6s Pearse 1938 r I Station t39.47 -33.67 SA om 138.23 -35.56 SA om ls(s) 68-72 Symon 1938 1 I Near Bullaparinga RAOU Atlas Data-base 1938 1 I Alawoona 140.50 -34.75 RAOU Atlas Data-base 1938 1 I Antechamber Bay (KI) 13 8.05 -35.82 1938 30 7 Woodside 13 8.88 -34 95 RAOU Atlas Data-base 1939 l I Morgan And Cadell Districts 140.79 -36-59 SA Om 1s(3) 38-46 Boehm t939 I I Curramulka t3'7.71 -14.70 SAOm l6(2) 1s-17 Souter -35.81 RAOU Atlas Data-base 1939 1 1 Antechamber Bay (KI) 13 8.07 McGilp t939 I 7 'üilmington I 38.10 -32.65 SA Om 1s(4) 61-64 Data-base 1939 13 I Naracoorte 140.78 -36.99 RAOU Atlas t939 26 7 Terka I 38.17 -32.70 RAOU Atlas Data-base t65 1940 - 1959 LOCATION YEAR DAY MONTH (Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER 1940 24 I Pamdana (KI) r37.25 -3 5.83 RAOU Atlas Data-base I 940 24 I Riverdale 136.84 -3s.94 RAOU Atlas Data-base 194 I I I Naracoorte t40.75 -36.97 RAOU Atlas Data-base SA Orn 17(1) 2-9 McGilp 1943 1 8 Granite Downs 133.50 -26.94 1943 9 8 Pigeon Bore Homeland 132.83 -27.00 RAOU Atlas Data-base t944 1l 6 Middle Beach r38.42 -34.58 RAOU Atlas Data-base 1944 I4 6 Adelaide 138.57 -34.89 RAOU Atlas Data-base t944 t6 7 Milner t38.47 -34.6s RAOU Atlas Data-base 1944 16 7 Two'ùy'ells 13 8.49 -34.58 RAOU Atlas Data-base Brooks t944 16 7 Buckland Park 138.48 -34.6s SA om l7(4) 31 McGilp 1945 I 8 Millicent Penola District 140.3s -3'7.60 SA om 17(8) 83 1945 I 7 Sixteen Mile Well 140.58 -37.50 RAOU Atlas Data-base 1945 20 9 Pukatja Homeland (Emabel la) 132.08 -26.25 RAOU Atlas Data-base t945 24 9 Itjinpiri Homeland 132.08 -26.24 RAOU Atlas Data-base 1945 I 10 False Cape (KI) 138.00 -3 5.83 RAOU Atlas Data-base 1946 I I Antechamber Bay (KI) 13 8.06 -35.82 RAOU Atlas Data-base 18(3) 22-24 Finlayson 1946 1 3 Thistle Island 136.r3 -34.98 SA om t946 t2 2 Observatory Point I 36. l5 -35.00 RAOU Atlas Data-base t946 29 9 Antechamber Bay (KI) l3 8,06 -35.79 RAOU Atlas Data-base Cleland 1946 30 9 Emabella t32.13 -26.29 SA Om l7(8) 83 SA Om 19(s) 42-49 McGilp t947 1 5 Andamooka t37.20 -30.73 McGilp t947 I 5 Ingomar 134.81 -29.66 SA Om l9(s) 42-49 t947 10 3 Moorundie 139.5 8 -34.42 RAOU Atlas Data-base t947 I 5 Andamooka 137.20 -30.73 RAOU Atlas Data-base Rix t947 l0 3 Blanchetown t39.62 -34.35 SAom l8(s)47 -34.00 RAOU Atlas Data-base 1948 1 I Hunchee 140.77 Atlas Data-base I 948 t4 8 Antechamber Bay (KI) 13 8.06 -35.80 RAOU ,) t949 l0 2 136.4s -35.15 RAOU Atlas Data-base 8 Brandon 1949 10 8 Horrocks Pass, Wilmington 1 38. l0 -32.65 SA om 20(1) 20(1) 3-5 Finlayson 195 l I I Wedge Island t36.46 -3 5.16 SA om l95 t 22 9 Eight Mile Comer 119.42 -34.42 RAOU Atlas Data-base Data-base 1955 I I Cape Bedout (KI) t36.63 -35.92 RAOU Atlas -35.95 R A,OU Atlas Data-base 1 955 I I Maupertuis Bay (KI) 136.73 1956 I I Cygnet River (Kl) 137.42 -i5.75 RAOU Atlas Data-base Data-base 1957 26 t2 Pennington Bay (KI) t3'7.78 -3 5.83 RAOU Atlas 195'l 26 t2 Poft Vincent 137.74 -34.80 RAOU Atlas Data-base t960 - 1979 1961 I Renmark t40.74 -34.17 SA om 23(4) 69-79 Mack t96t I Picnic Beach 135.93 -34.70 RAOU Atlas Data-base 1964 I Kanni 139.98 -34.25 RAOU Atlas Data-base t964 I Aldinga 138.47 -35.27 RAOU Atlas Data-base 1964 I Little Toolunka Flat, Near Waikerie t39.95 -34.11 SA Om Bird Report 1964 t66 LOCATION YEAR DAY MONTH l'Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER 1964 I 10 Harts Lagoon, Waikerie r39.96 -34.t7 SA Om Bird Report 1964 t964 22 4 Langhome Creek 139.0s -35.34 RAOU Atlas Data-base 1964 1 9 Nevarda 139.92 -34.25 RAOU Atlas Data-base 1964 7) 4 Langhome Creek 139.03 -35.30 SA Om Bird Report 1964 ,) 1965 T4 2 t36.42 -35.17 RAOU Atlas Data-base 1965 1 7 Tookayerta 140.50 -34.50 RAOU Atlas Data-base 1965 '7 8 Oodla Wirra 139.05 -32.88 RAOU Atlas Data-base t965 13 5 Langhome Creek 139.03 -35.30 SA Om Bird Report 1965 l 965 2 t4 Wedge Island 136.46 -35 16 SA Om Bird Report 19ó5 Data-base t966 1 I Milang t38-97 -35.3s RAOU Atlas Data-base 1 966 I I False Cape (KI) t37.92 -3 5.83 RAOU Atlas ,l t966 31 I 136.25 -34.60 RAOU Atlas Data-base 1966 31 I Reevesby Island t36.36 -34.54 SA Om Bird Report 66-67 1967 I I Milang-Langhorne Creek Area 139.03 -35.30 SA Om Bird Report 1966-67 t967 23 6 Meningie 139.35 -35.65 RAOU Atlas Data-base 1967 26 7 Spilsbey Island I 36.19 -34.65 SA Om Bird Report 1967-68 Kraehenbuehl, K 1 968 I I Aldinga Scrub 13 8.45 -35.29 SAOA I 968 I 1 Yakilo'(KI) 136.92 -35.7 5 RAOU Atlas Data-base 1967-68 I 968 1 6 Belvidere 138 94 -35.29 SA Om Bird Report l 968 I 5 Strathalbyn 13 8.95 -3 5.30 RAOU Atlas Data-base Data-base 1968 1 7 Kingston-On-Murray t40.25 -34.25 RAOU Atlas I 968 12 8 Wolseley t40.9t -36.37 SAOA Williams 1968 8 t2 Custon 140.90 -36.47 RAOU Atlas Data-base ,) 1969 I I 137 08 -35.75 RAOU Atlas Data-base 1969 I I Antechamber Bay (KI) 138.04 -3 5.8 I RAOU Atlas Data-base t969 30 3 Monash 140.58 -34.25 RAOU Atlas Data-base 1969 30 3 Lyrup t40.62 -34.22 RAOU Atlas Data-base 1969 I 7 Morgan t39.67 -34.03 RAOU Atlas Data-base 1969 I 7 Glossop 140.53 -34.27 RAOU Atlas Data-base 1969 I 7 Keynes Hill 1 39.15 -34.5',7 RAOU Atlas Data-base t969 7 9 Woolpunda t40.22 -34. I 8 SA Om Bird Report 1969-10 1969 t4 l1 Keynes Hill r 39.08 -34.58 RAOU Atlas Data-base t969 30 J Winkie 140.52 -34.31 SA Om Bird Report 1969-70 t970 I I Keyneton (5 Mls N Lk Meneti) 133.15 -34.56 SA Om Bird Report 1969-70 r9'70 I I Glossop 140.53 -34.27 SA Om Bird Report 1969-70 t970 t4 6 Milang t38-92 -35.42 RAOU Atlas Data-base 1970 I 7 Lowbank t40.14 -34.23 RAOU Atlas Data-base t970 13 7 Woolpunda t40.22 -34.1 8 SAOA Thom 1970 22 10 Between Ashbourne And Finiss 138.77 -35.29 SAOA Ragless Eckert t97 I 11 1 Near Milang 138.97 -35.41 SAOA t97l 30 ll Eastern Cove (KI) t37.90 -35.80 RAOU Atlas Data-base 1972 I 6 Elizabeth 138.63 -34.70 RAOU Atlas Data-base 1972 18 7 Elizabeth 138.70 -34.70 RAOU Atlas Data-base 1972 2l 7 St Kilda 138.58 -34.75 RAOU Atlas Data-base r972 30 8 Snug Cove (KI) 1 36.84 -35;70 SAOA Vincent t67 YEAR DAY MONTH (Nearest Named PIace) LATITUDE LONGITUDE SOURCE OBSER\IER 1973 I I Waterhouse Point t36.17 -3 5.03 RAOU Atlas Data-base 1973 1 1 Antechamber Bay (KI) 138.06 -35.81 RAOU Atlas Data-base 1973 1 4 Brigadoon 136.72 -35.88 RAOU Atlas Data-base 1973 8 10 Observatory Point I 36. l0 -34.96 RAOU Atlas Data-base t974 1 I Antechamber Bay (KI) l3 8.04 -3s.82 RAOU Atlas Data-base t974 I 3 Wirrelyema 140.22 -34 l8 RAOU Atlas Data-base 19'74 I 10 Kingscote (KI) t37.63 -35.65 RAOU Atlas Data-base t974 26 J Woolpunda t40.22 -34. l 8 SAOA Thom l97s 1 I Pioneer Bend' (KI) t37.25 -35;7 5 RAOU Atlas Data-base 1975 I 1 Beachport 140.01 -37.48 RAOU Atlas Data-base 1975 I I Antechamber Bay 138.05 -3 5.83 RAOU Atlas Data-base 1975 4 9 Boston Island 13 5.93 -34.70 SA Om Bird Report 1975 r975 l4 9 Picnic Beach 135.92 -34.70 RAOU Atlas Data-base t975 2l 9 Observatory Point 136.12 -34.98 RAOU Atlas Data-base t975 1 12 Brigadoon 136.83 -35.92 RAOU Atlas Data-base ,) 1975 26 t2 136.s0 -35.50 RAOU Atlas Data-base t975 2l 9 Thistle Island 136.13 -34.98 SA Orn Bird Report 1975 1976 I 1 Observatory Point 136.10 -34.95 RAOU Atlas Data-base 1976 24 I 'Waterhouse Point t36.1'7 -3 5.0 I RAOU Atlas Data-base t976 28 2 KI, D'estrees Bay 137.58 -35.92 RAOU Atlas Data-base r976 16 4 Hunchee r40.7 5 -34.03 RAOU Atlas Data-base t976 I l0 Trecompana Hill 136.50 -29.50 RAOU Atlas Data-base t976 l5 t2 Cape Tonens (KI) 136.75 -35.75 RAOU Atlas Data-base t976 l5 8 Thistle Island 1 36. r3 -f4.98 SA Om Bird Report 1976 1976 15 8 Wrattonbully 140.96 -37.17 SA Om Bird Report 1976 t976 25 9 5km S Nunns Bore t36.52 -29.09 SA om 28(2) Badman t977 I I Cape Coutts 138.04 -35.77 RAOU Atlas Data-base t977 I I Vy'aterhouse Point 136.18 -3 5.0s RAOU Atlas Data-base r977 J I Brigadoon 136.76 -35.91 RAOU Atlas Data-base t977 4 I KI, False Cape t37.91 -3 5.85 RAOU Atlas Data-base t977 4 I Brigadoon 136.73 -35 91 RAOU Atlas Data-base t977 26 I 2 136.50 -3s.50 RAOU Atlas Data-base 1977 26 1 Brigadoon t36.75 -35 93 RAOU Atlas Data-base t977 7 2 Pennington Bay (KI) t37.74 -35.85 RAOU Atlas Data-base t977 22 4 Brigadoon 136.75 -35.91 RAOU Atlas Data-base 1977 l8 8 Coombool (Outstation) t40.92 -33.92 RAOU Atlas Data-base 1977 I 9 Port Lincoln Proper t35.92 -34.80 RAOU Atlas Data-base t977 25 9 Sleaford Bay 135.7 5 -34.85 RAOU Atlas Data-base 1977 29 l1 Brigadoon t36.73 -35.92 RAOU Atlas Data-base t977 2 12 Warrawee t37.29 -35.92 RAOU Atlas Data-base t977 19 6 Milang t38.97 -35.41 SAOA Opie 1978 I 8 ? 137.08 -35.76 RAOU Atlas Data-base 1978 27 8 West Bay (KI) 136.58 -3 5.89 RAOU Atlas Data-base 1978 29 8 Cape Borda (KI) t36.61 -35.77 RAOU Atlas Data-base 1978 l 9 Triyana 140.77 -36.86 RAOU Atlas Data-base 168 LOCATION YEAR DAY MONTH fNearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER Ashton I 978 9 8 Aldinga Scrub 138.45 -3s.29 SAOA Data-base 1978 1 10 Cape Dutton 137.08 -3s.73 RAOU Atlas I 978 7 l0 Brigadoon 136.77 -35.91 RAOU Atlas Data-base 1978 9 l0 Cape Du Couedic (KI) 136;74 -36.03 RAOU Atlas Data-base t978 14 10 Naracoorte 140.78 -36.92 RAOU Atlas Data-base l 978 I ll Naracoorte r40.67 -36.93 RAOU Atlas Data-base t978 I 12 Brigadoon t36.92 -35.92 RAOU Atlas Data-base r978 ll l2 Brigadoon 136.76 -35.93 RAOU Atlas Data-base t9'78 t2 12 Brigadoon 136.74 -35.92 RAOU Atlas Data-base Possingham r978 24 8 3km W Rocþ River (KI) t36.71 -35.9s SAOA Cox I 978 27 8 Harvey's Retum (KI) t36.64 -3s 75 SAOA t979 I t Cape Bedout (KI) 136.58 -f5.92 RAOU Atlas Data-base t979 I I Vivonne Bay (KI) t37.25 -35.92 RAOU Atlas Data-base t979 I I Castle Hill (KI) 137.06 -35.74 RAOU Atlas Data-base r979 5 I Brigadoon 136.74 -35.92 RAOU Atlas Data-base t979 )n I Yakilo'(KI) 137.05 -35 77 RAOU Atlas Data-base 1979 I 3 Cape Dutton 137.1 1 -35.74 RAOU Atlas Data-base Black Tank, 6km WNW Mack and Comish t979 J 11 Taylorv.ille 139.98 -34.10 SAOA r979 20 3 Kybybolite 140.92 -36.92 RAOU Atlas Data-base t979 25 3 Brigadoon t36.77 -35.92 RAOU Atlas Data-base ,l 1979 I 4 I 37.10 -35.76 RAOU Atlas Data-base Baxter t979 11 4 Gravel Pit N Rem. Rocks (KI) t36.70 -3ó.04 Pers. comm. Atlas Data-base t979 1 5 Cape Bouguer (KI) t36.92 -36.02 RAOU t979 I 5 Cape Dutton (KI) 1 37.1 0 -35.75 RAOU Atlas Data-base 104-6 Bonnin t979 5 2 Wedge Island t36.46 -35. I 6 SA Om 28(4) ,| t979 3l 5 t 39.58 -27.75 RAOU Atlas Data-base t9'79 I 6 Castle Hill (KI) 137.05 -35.7) RAOU Atlas Data-base ,) Q) t979 2 6 139.58 -)1 RÀOU Atlas Data-base r979 2 6 Brigadoon t36.75 -35 92 RAOU Atlas Data-base Data-base t979 3 6? 137.08 -35.77 RAOU Atlas Data-base t979 5 6? t39.42 -27.92 RAOU Atlas Data-base 1979 I 7? I 37.10 -35.76 RAOU Atlas t979 f 7 Point Morrison t!7.75 -35.75 RAOU Atlas Data-base RAOU Atlas Data-base r979 3 l Kangaroo Head t37.92 -35.7 5 Baxter t979 1l 7 Kelly Hill Caves (KI) 136.90 -3 5.98 Pers. comm. Baxter t979 9 I 2 km W Rocky River (KI) t36.7 | -35.95 Pers. comm. t979 I 9 Triyana 140.69 -36.87 RAOU Atlas Data-base t979 I 9 Yinkanie 140.26 -34-31 RAOU Atlas Data-base t979 I 10 Observatory Point 136.1 I -34 94 RAOU Atlas Data-base -35.05 RAOU Atlas Data-base t979 1 l0 Waterhouse Point I 36.16 Baxter 1979 l1 1l 1Okm West Vivonne Bay (KI) 137.07 -35.99 Pers. comm. r979 l6 ll Westem Cove (KI) t37.56 -35;79 RAOU Atlas Data-base t9'79 I t2 Kingston-On-Murray 140.31 -34.23 RAOU Atlas Data-base t979 I t2 Cape Dutton (KI) 137.08 -35;73 R A,OU Atlas Data-base Baxter t979 12 5 Yakka Flat Rd (Kl) 136'73 -36.02 Pers. comm. t69 LOCATION YEAR DAY MONTH (Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER Thomsen 1979 13 3 Waite Research Establ ishment 138.63 -34.97 SAOA t979 t7 7 Cape du Couedic Road (KI) 136.74 -35.98 Pers. comm. Baxter 1979 20 3 Near Hynam t40.62 -36;78 SAOA Attiwill 1979 25 9 Edinburgh Air Base, Salisbury t38.62 -34.71 SAOA Whibley 19't9 28 t2 South Coast/Mt Taylor Rd (KI) t37.04 -35.99 Pers. comm. Baxter 1980 - 1995 1980 l I Cholla 140.75 -36.25 RAOU Atlas Data-base Pers. comm. Baxter 1980 1 4 lOkm West Pamdana (KI) 137.16 -35.80 Thom 1980 I 9 Woolpunda t40.22 -34.18 SAOA -35.75 RAOU Atlas Data-base 1980 29 1 Snapper Point 138.03 Baxter 1980 2 4 Sunshine Ave' South Coast Rd (KI) 136.87 -35.98 Pers. comm. 1980 I 4 Naracoorte t40.75 -36.92 RAOU Atlas Data-base Data-base 1980 3 4 False Cape (KI) t37.95 -3s.86 RAOU Atlas 1980 26 4 Kanbara t37.44 -35.78 RAOU Atlas Data-base 1980 27 4 Yakilo'(KI) 136.90 -35.76 RAOU Atlas Data-base 1980 28 4 Cape Borda (KI) 136.58 -35.79 RAOU Atlas Data-base Atlas Data-base 1980 3 5 Hummocky Point (KI) r37.25 -35.62 RAOU 1980 4 5 American River (KI) t37.72 -35.79 RAOU Atlas Data-base Between Ravine And'Borda Park' Pers. comm. Baxter 1 980 I 6 (KD 136.68 -35.76 Data-base 1980 ll 7 Tungketta Hill 135.06 -33.75 RAOU Atlas 1980 I 8 Kurlana r40.17 -34.29 RAOU Atlas Data-base 1980 I 9 Kewson Hill 136.7 s -29.42 RAOU Atlas Data-base Atlas Data-base I 980 I 10 Pioneer Bend t37.12 -35.7 s RAOU 1980 t6 l0 Cape Tonens (KI) 1f6.74 -35.74 RAOU Atlas Data-base 1980 18 10 Cape Tonens (KI) t36.74 -35.76 RAOU Atlas Data-base l 980 I t2 Hurst Plain 139.73 -34.14 RAOU Atlas Data-base ,l Atlas Data-base 1980 1 t2 r40.27 -34-r9 RAOU Data-base t 980 t2 L2 Tamara t40.74 -36.43 RAOU Atlas Baxter 1980 15 7 West Bay Blowhole (KI) 136.56 -3 5.88 Pers. comm. Baxter 1980 18 2 Rex Ellis'- Ravine (KI) 136.68 -35.76 Pers. comm. Joseph 1980 l9 l0 lOkm E Hawey's Retum (Kl) 136.74 -35.79 SAOA West Bay Rd Near Sandy Creek Baxter 198 r I 8 (KI) 136.64 -35.95 Pers. comm. 1981 I 3 Hurst Plain t39.7s -34.08 RAOU Atlas Data-base Data-base 1981 I 6 Hurst Plain 139.82 -34.t3 RAOU Atlas 1981 I 9 Bundilla 139.81 -14.19 RAOU Atlas Data-base Baxter 1981 ll 9 Shackle Rd Nth of Airstrip (KI) t36.7r -35.92 Pers. comm. 1981 18 9 Farina 138.25 -30.08 RAOU Atlas Data-base Baxter 1981 l0 I Playford Hwy/Snug Cove Rd (KI) 136.88 -3 5.78 Pers. comm. Data-base l98l 9 10 Cholla r40.73 -36.26 RAOU Atlas 1981 I 11 Castle Hill (KI) t37.05 -35.7 5 RAOU Atlas Data-base Data-base l98l 5 t2 Custon r40.92 -36.42 RAOU Atlas Baxter 1981 18 4 Gosse Community Centre (KI) 136.98 -35.80 Pers. comm. Baxter l98l 30 ll 1.2km South Rockv River (KI) 136.t4 -35.96 Pers. comm. 170 LOCATION YEAR DAY MONTH (Nearest Named Place) LATITUDE LONGITUDE SOURCE OBSERVER Ellis 1982 I l0 6km E Ravine Des Casoars (KI) 136.74 -35;79 SAOA Baxter t982 6 t2 Cape du Couedic Rd (KI) 136.75 -35.9'7 Pers. comm. Cox 1982 t4 10 Mt Remarkable 13 8.06 -32.80 SAOA Baxter 1982 16 9 Vy'est Melrose Track, FCNP (KI) 136 67 -35.92 Pers. comm. _1< r5 Foreman t982 20 8 lOkm SE Tailem Bend 139.45 SAOA Houston 1982 29 t2 Bordertown 140.77 -36.32 SAOA Robby Beckwiths, South Coast Rd Pers. comm. Baxter I 983 I 3 (KI) I 36.80 -3s.96 Smith 1984 10 1 Boston Island 135.93 -34;70 SAOA Dennis, T 1984 12 4 12km Sw Kingscote (KI) 13'7.52 -35.70 Museum Baxter l 984 t4 4 Roo Lagoon (KI) t37.04 -35.80 Museum Sth Coast Rd N Of MunaY Lagoon Dennis 1985 19 9 (KD t37.41 -35.88 Museum Museum Dennis I 985 30 11 6km E Pamdana (KI) t37.33 -3 5.78 Schmidt per Carpenter t987 t2 I lOkm Nw Bower 139.3 5 -34.13 SAOA -3 Museum McKelvey, M I 987 23 2 Pelican Lagoon 137.81 5.8 I NCSSA Survey 1988 ll 8 Chowilla Floodplain 140.84 -34.03 SAOA Pers. obs. Gates 1989 I 1 Fenies McDonald CP t39.r4 -3s-23 -3 Museum Fumer I 989 21 8 FCNP (KI) 136.74 5.95 Wilson, G 1991 24 6 2km S Pamdana (KI) t37.26 -3 5.8 I Museum comm. L Pedler t992 l9 9 Section 108 McgillivraY (KI) 13'7.4r -35.90 Pers. comm. L Pedler t992 t9 9 Section 112, McgillivraY (KI) t37.43 -35.90 Pers. L Pedler t992 l9 9 Section 89, Mcgillivray (KI) t37.45 -35.90 Pers. comm. L Pedler 1992 l9 9 Section 90, McgillivraY (KI) 137.46 -35.90 Pers. comm. comm. L Pedler t992 19 9 Section 18, Mcgillivray (KI) t37.38 -35.84 Pers. L Pedler r992 19 9 Section 10, McgillivraY (KI) t37.49 -35.90 Pers. comm. L Pedler t992 t9 9 Section 4, McgillivraY (KI) 137.43 -35.89 Pers. comm. L Pedler 1992 l9 9 Section 8, Mcgillivray (KI) 137.50 -35.91 Pers. comm. L Pedler t992 l9 9 Section 57, Mcgillivray (KI) 13'7.43 -35.88 Pers. comm. comm. L Pedler 1992 19 9 Macgillivray (KI) t37.44 -3 5.9 I Pers. Halstead 1992 2l I Haniet Rd (KI) 137.ll -35.82 Museum Ellis t993 24 t2 Near Cadell 140 79 -36.59 SAOA Ball, D/St. John, B 1994 l6 12 Gosse-fuchie Rd (KI) 136.96 -35.86 Museum Dennis t994 l9 6 American River (KI) t37.77 -35.79 Museum 'Werta Matthew r994 t9 t2 Wert Chowi'lla 140.87 -33.94 SAOA Croft I 995 10 l1 Mundulla Parklands r40.69 -16.36 SAOA O'Brien and McAllan t995 l3 6 Bordertown r40.77 -36.32 SAOA Bookmark Bio Trust t996 2 2 Reny Island 140.73 -34.06 Pers. comm. Bookmark Bio Trust 1996 2 3 Hunchee Island t40.79 -34.05 Pers. comm. t7l APPENDIX 2. SUMMARY OF COMMUNITY QUESTIONNAIRE RESULTS. A total of 64 questionnaires were returned (approximately l3%). All responses were positive (i.e. bush stone-curlews were present on landholders properlies). All results are shown as percentage of responses. Yes - 100% No-0% If YES, when? Last Week -34% Last 6 months -22% Last month -25% Last Year -22% Yes -76Yo No -24o/o If YES, where have you seen them? (tick as appropriate) Open paddock (grazed) - 19% Open paddock (ungrazed) - lYo Within native vegetation (grazed) - 48% V/ithin native vegetation (ungrazed) -29% In semi-cleared paddock- 23%o Other - 3Yo (creeklines, roadsides) Yes -72Yo No - 28% If YES, where have you seen them? (tick as appropriate) Openpaddock (grazed)-51% Openpaddock(ungrazed)-14% Within native vegetation (grazed) -26% Within native vegetation (ungrazed) - 14% In semi-cleared paddo ck- 30%o Other - 60/o (pine forest, creeklines, and roadsides) Q3: Have you ever seen nests/eggs/chicks? Yes - 48o/o No - 52% If YES, please indicate where you have seen nests? (tick as appropriate) Open paddock (grazed) -30% Open paddock (ungrazed) - lYo Within native vegetation (grazed) - 30% Within native vegetation (ungrazed) - 17% In semi-cleared paddock- 27Yo Other - Il% þine forests, open paddock with scattered trees, town parklands, driveway) Yes - 5% No - 95%. 172