Corella,2006, 30(2): 41-45 BREEDINGBIOLOGY OF THE AUSTRALIANWHITE ThTeskioTnis moluccaAT AN URBANBREEDING COLONY SOUTH-EAST QUEENSLAND

NICHOLAS J. MURRAY''2 and PHILLP P. SHAW'

rBcosure, PO Box 287 Tugun, Queensland, Australia 4224. E-mail: [email protected] 2Centre for Innovative Conservation Strategies, Griffith University, Gold Coast, PMB 50, Gold Coast Mail Centre, Bundall, Queensland 9726

Received: 30 November 2005

The AustralianWhite lbis Threskiornismolucca has increasedin rangeand abundancein Australiasince Europeansettlement, and has recentlyreached pest proportionsin urbanenvironments. Aspects of Australian Whitelbis breedingecology at an urbanbreeding colony on the GoldCoast, Queensland were studied in the 200212003breeding season. Breeding activity commenced in lateJune and lastedfor six months,with the last egghatched in lateDecember. A totalof 124clutches was initiatedin 95 nests,and a furtherten nestsproduced no eggs.Themean clutch size was 2.46 eggs and the meanincubation period was 21.61 days. Hatching success was47.9 per cent, fledging success was 60.3 per cent and overall breeding productivity, that is the proportionof chicksfledged to eggslaid, was 28.9per cent.Results reported here may be usedin optimisingthe timingof visitationto urbanbreeding colonies for implementationof ibis managementprogrammes that are aimedat controllingurban Australian White lbis populations.

INTRODUCTION performance and nest abandonment of other native The large-scaleconversion of natural and agricultural waterbird (Kentish 1994, 1999). Large numbers of areasto urban environments has led to dramatically altered in urban areas also have a coastal habitats (Adams 1994; Maruluff 2001). Whilst detrimental effect on human social values and. therefore. urban areas typically contain reduced fauna diversity may be considereda pest species(Bomford and Sinclair compared to surrounding areas, some species have 2002). As opportunisticforagers, they scavengeon human colonized the urban environmentand have benefitedfrom food waste in a variety of urban environments(Marchant anthropogenic food sources, increased protection from and Higgins 1990) and are known to harbour a variety of predators,permanent water sources and the presenceof pathogens,which may present a risk to humans (Epstein suitable breeding sites (Blair 1996; Marzluff 2001). 2001; McKee 2OO2).Furthermore, Australian White Ibis Compared to their non-urban counterparts, urban pose a significant risk to air safety at severalAustralian 'winning' populations of avian specieshave exhibited metropolitan airports (Shaw 1999; Australian Transport longer yearly breeding seasons,earlier onset of breeding Safety Bureau 2003). within the season, and increased breeding success and The negative impacts of Australian White Ibis survival rates(Perrins 1970; Svensson1995; Rollinson and populations in urban areas have led to the formulation of Jones2002; Parteckeet a\.2005). broad scale managementprogrammes (Shaw 1999; Ross The Australian White Ibis molucca is one 2004). Managementstrategies have included egg and nest of only a few Australian waterbird species to have disturbanceat breeding colonies, culling, habitat modifi- increasedin range and numbers in recent years (Blakers cation, active dispersal and physical exclusion from et al. 1984; Kentish 1999; Kingsford and Norman 2002; foraging sites (Ross 2004; Shaw and Murray 2OO4).Egg Barrett et al.2004). This has been attributed to the increase and nest disturbance,including egg and nest destruction, in suitable habitats through the conversion of land for removal of eggs, egg replacement,egg pricking and egg agriculture, the utilization of new and constant food sources oiling requires regular repeated visitation during the and broad habitat tolerance (Kentish 1999). Urban breeding season.Information on the breeding biology of populationsof ibis have also increasedconsiderably since Australian White Ibis in urban areas may be used to the 1970s (Ross 2004). Suspectedcauses for the increase optimize timing of visitation to urban breeding colonies, include the relocation of natural populations as a response which will increase the efficiency of management to inland drought, exploitation of anthropogenic food programmes for those that rely on the managementof sources. translocation of individuals and increased urban breeding colonies. protection of nesting colonies (Shaw 1999; Ross 2004). Several studies have reported on the breeding biology of Breeding colonies of Australian White Ibis are now Australian White Ibis in natural environments (Lowe 1984; common in many urban centres (Nick Murray, pers. obs.). Beilharz 1988; Kentish 1999). However, despite being a At urban breeding colonies, damage to remnant common species in many urban areas and the reported vegetation and faecal contamination of water bodies caused conflicts with humans, few studies on ibis breeding biology by high densitiesof nestingAustralian White Ibis have led have been conducted in an urban context. In this paper, to elevated nutrient levels at some sites. and lower breedins data on the breeding biology of Australian White Ibis in

41 42 N. J. Munay and P. P. Shaw: Breeding biology of the Australian White lbis Corella30(2) an urban environmentare presentedand management by examining the egg and differentiating between the recently laid optionsfor pestpopulations are discussed. whiter eggs and older, dirtier eggs. Where laying order could not be determined, eggs were excluded from the analysis of eggs size. Care was taken during monitoring to ensure that disturbance of ibis in the METHODS colony was kept to a minimum.

Clutch size was defined as the maximum number of eggs observed Study site in one nest. Reproductive success was assessedin terms of (l) hatching The breeding biology of an urban Australian White Ibis population success (t}le proportion of eggs hatched to the number of eggs laid), (2) at Movieworld Lake, south-east Queensland (27'55'S, 153'19'E) fledging success (the number of chicks which reached 21 days old or between luly 2002 and June 2003 was studied. Movieworld Lake drains were capable of flight as a proportion of the number of chicks hatched) from an urban catchment and is approximately one hectare in size. The and (3) overall breeding productivity (the number of chicks fledged as lake is largely open shallow water (up to 1.5 m deep) with some areas a proportion of the number of eggs laid). Because chicks were not exposed as mudflats during periods of little rain. The site is dominated individually marked and often departed the nest at approximately nine by Melaleuca quinquinervia, which forms clusters within the waterbody days old to form groups with neighbouring chicks, fledging successand and provides nesting sites for several ibis pairs in any one aggregation. breeding productivity were determined for groups of nests as opposed Sunounding Movieworld Lake are areas of urban development, farmland to individual nests. Despite fledglings roosting and foraging at the site and a theme park. Two waste landfills are potential foraging sites - a for several weeks after fledging from the nest the successof chicks from putrescible waste landfill 2l kilomehes to the north and a general waste fledging to independence could not be determined. Breeding pairs were landfill nine kilometres to the south of the breeding site. Australian not individually identified and, therefore, it was not possible to determine White Ibis have been recorded breeding at Movieworld Lake in all years the number of clutches produced by one pair for the breeding season. since observations began in 1998, and no management of the breeding colony has been undertaken at the site. RESULTS

Colony occupation Colony occupation

Counts of Australian White Ibis roosting at Movieworld Lake were Australian White Ibis were presentat Movieworld Lake conducted during the study period, from July 2002 to June 2003. Week-ly in all months between June 2OO2and June 2003 (Fig. 1). counts were conducted early in the breeding season,and then fortnightly Maximum counts occurred in early August 2002 (284 last from October onwards. Commencing approximately two hours before individuals)and in March 2003 (308 individuals).Numbers light, all ibis at the colony were counted. Subsequently, counts of all ibis entering and leaving the colony were made until approximately ten of Australian White Ibis roosting at the colony were usually minutes after last light and the number of ibis, which roosted overnight, higher between July and December,when nesting was was calculated. Weekly counts were conducted during the 2002 breeding observed(Fig. 1). season. Nests,eggs and clutches Nest monitoring During the 2002 breeding season, a total of 105 active The Movieworld Lake colony was visited three times per week during nests was located at Movieworld Lake. Nests were the 2002 breeding season, from 15 July 2002 until all chicks fledged predominantly found over water in mature Melaleuca trees (31 = visits). Every nest in the colony was January 2003; n 86 metreshigh individually marked with flagging tape and on each visit new nests were (93.3Vo)but some nestswere built up to eight identified. During each visit, the content of each nest was recorded. in eucalyptssurrounding the lake (6.7Vo).Nests were built Whel first encountered, eggs were weighed to the nearest gram using either singly or in aggregationsand were constructedfrom digital scales, measured to the nearest 0.02 millimetres with vernier interwoven small to medium sticks and were occasionally (length width) and marked with a felt-tipped pen. calipers and maximum lined with fresh eucalypt leavesimmediately before laying. The laying order of eggs and incubation period were determined by + marking the eggs in numerical order. In cases where two or more eggs Mean number of nests in each aggregationwas 4.6 2.1 were laid betweenvisits, it was usually possible to establishlaying order nests(range = l-l 1, n = 26 aggregations).

350

300

250

f zoo

150 :

100

50

Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr l{ay Jun 2aoz 2oo3

Figure l. Number of Australian Wite lbis counted during roost counts at Movieworld between I I June 2002 and 28 June 2003. June.2006 N. J. Munayand P P Shaw:Breeding biology of the AustralianWhite lbis 43

-l-No. of eggs 120 --O- No. of chicks

o t too

gl g80 (', o o d60 z

Jul Aug sep Oct Nov Dec Jan Feb Month

Figure 2. Number of eggs and chicks recorded per visit at Movieworld breeding colony from 15 July 2002 to 3l January 2003 (n = 86 visits).

During the first visit in the 2OO2breeding season(July Complete nest failure was common, with 46.8 per cent of 15), several nests contained eggs and the first eggs to hatch all clutchesinitiated, failing. Causesof egg mortality were were observed. On the basis of hatching dates and not known becauseegg loss was mostly attributed to the incubation periods (see below), egg-laying most likely disappearanceof eggsbetween visits. Heavy rainfall on 21 began in the week beginning 23 June 2002. In total, 305 August resulted in ten nests being submerged. The eggs were laid during the 2002 breeding season.Laying mean incubation period, defined as the time elapsed was concentratedin the early stageof the breedingseason between when an egg was first encounteredto when it with 58 per cent of all eggs laid within 60 days after the hatched,was 21.61 + 1.35days (range= 1824 days,n = fust egg was estimatedto have been laid (Fig. 2). A second 4l eggs). After hatching, eggshells were usually ejected peak in laying was recorded in September.The last egg from the nest. hatched on 27 December. The mean length and width of a subsampleof 124 eggs were 63.62 millimetres and42.97 A total of 88 chicks fledged from the 95 nestscontaining millimetres respectively,which are amongst the smallest eggs. Fledging successwas 60.3 per cent and overall eggs observedin this species(Table 1). Egg sizes within breedingproductivity was 28.9 per cent. Chick losseswere clutches were not significantly different and clutch size had mainly attributable to their disappearancebetween visits, no significanteffect on egg size. although several dead chicks were found in and around A total of 124 clutches was initiated in 95 nests,and no nests. There was no direct observation of predation at eggs were recorded in a further ten nests which were Movieworld Lake during the study period, and no chicks considered active due to their structure and form. The found dead showed any visible indication of predation.In mean clutch size at Movieworld Lake was 2.46 + 0.7 eggs some cases adults from adjacent nests were observed (range= 14, n = 124 clutches;Table 2). The modal clutch attackingchicks, which ventured into their nests,although size was three eggs. Hatching successwas 47.9 per cent. no deathswere recorded.

TABLE 1 Dimensions of Australian White Ibis eggs at Movieworld Lake, south-east Queensland and various locations in Victoria.

Mean Location Length Width

Movieworld Lake, Queensland 124 63.62 42.97 This study Lake Cowal, Victoria 24 66 45 Vestjens 1977 (cited in Marchant and Higgins 1990) Phillip Island, Victoria t66 66.45 43.9 Marchant and Higgins (1990) Rhyll, Victoria 33 66.4 44 Lowe (1984) Rhyll, Victoria 84 66.3 43.8 Lowe (1984) Coolart, Victoria 60 67.1 43.6 Lowe (1984) Healesville, Victoria 36 64.6 42.4 Lowe (1984) 44 N. J. Munayand P.P Shaw:Breeding biology of the AustralianWhite lbis Corella30(2)

TABLE 2 Variation in the breeding biology and timing of within speciesis known to occur across Summary of the reproductive parameters of Australian White Ibis at reproduction Movieworld Lake, south-east Queensland, during the 2002 breeding populations living at different latitudes, as well as among season(mean + S.E.). Hatching successis the proportion of eggs hatched subpopulations which utilise different habitats, food to the number of eggs laid. Fledging success is the proportion of chicks resources,or are subject to differing rates of nest predation total number of eggs hatched. Breeding that fledged from the nest to the (Svensson 1995; Partecke et al. 2005). Furthermore, productivity is the number of chicks that fledged as a proportion of the number of eggs laid. quality, availability and consistencyof food resourcescan influence timing of breeding and reproductive successtn Breeding parameter 2002 breeding season (Perrins 1970; Svensson1995). Severalstudies have Egg dimensions reported extendedbreeding seasonsand increasedsuccess -- Mean egg length (mm) 63.62!'7.81 (n 124 eggs) in colonial bird speciesobtaining food from waste landfills + (n -- 124 eggs) Mean egg width (mm) 42.97 3.0"1 (Belant et al. 1998; Tortosa et al. 2002; Yorio 2002). incubation period (daYs) 2l.62* 1.36(n = 41) Mean it should be noted that other factors such Mean clutch size (eggs) 2.46x 0.71(n = 124clutches) However, 7o clutch failed before hatching 46.8 as latitude, rainfall, environmental predictability and Success prevailing weather conditions were not addressedin this Hatching success 4'l.97o study (Halse and Jaensch1989; Bildstein et al. 1990). Fledging success 60.3Vo Breeding productivity 28.9Vo As in other colonial birds, ibis are susceptibleto human disturbanceat breeding colonies and increasedpredation, exposureand stressas a result of human disturbanceis well (Gotmark 1992; Hancock e/ DISCUSSION documentedin the literature al. 1992). In this study, observer disturbance may have Australian White Ibis at Movieworld Lake bred either affected breeding performance, despite the precautions singularly or in aggregations, and were recorded in a taken to avoid this. Egg and chick predation is a major variety of nesting sites including aggregationsover water cause of breeding failure in many speciesof ibis (Miller and single nestsin trees.Variability in nestingsites has also and Burger 1978;Donazar et al. 1994;Bowden et a\.2003; been observed at other nesting sites in urban areas of Olmos 2003). Lowe (1984) reportedscavenging by ravens south-eastQueensland where ibis commonly nest in tall Corvus sp. and Red Fox Vulpes vulpes on carcassesand eucalypts, rainforest remnants, Norfolk Pines and Cocos abandonedeggs at some Australian White Ibis breeding Palms (Nick Munay, pers. obs). Elsewhere,ibis have been colonies. In this study, no incidences of predation were recorded nesting in a similar range of environments observed. including clumps of mistletoe in eucalypts, bare ground and artificial structures (Carrick 1962; Marchant and Managementimplic ations Higgins 1990). In Australia, a range of methods has been used for the The mean clutch size,clutch failure rate, fledging success managementof Australian White Ibis populations.Direct and overall breeding productivity found in this study was managementof ibis breeding colonies through egg and nest similar to that recorded in New South Wales and Victoria destruction,egg suppressionthrough oiling or pricking and (Carrick 1962:Lowe 1984;Beilharz 1988;Kentish 1999). culling of selectedindividuals is undertakenwidely (Ross The breeding season at Movieworld Lake lasted seve.n 2004; Shaw and Murray 2005). Resultsreported here may months, with the onset of egg laying in late June. Lowe be used in optimising the timing of visitation to urban (1984) studied the breedingof Australian White Ibis at breeding colonies for implementation of management several breeding colonies in Victoria and found that ibis programmeswhich include egg and nest destructionor egg breeding in colonies at inland and coastal sites exhibited suppression. variable breeding seasonslasting up to five months. The suggest that managementof presenceof abundantanthropogenic food sourcesresulted The results of this study to influence the timing in extendedbreeding seasons in somecolonies. One colony anthropogenicfood sourcesis likely of Australian White at HealesvilleVictoria, supportedby a wastelandfill, began of breeding and reproductivesuccess Shaw (2001) reportedthat breeding up to one month earlier than all other sites, with Ibis in urban environments. site for between 66 and the breedingseason lasting from June to December(Lowe landfills were a significant foraging population of ibis on the Gold 1984). Similarly, a seven-monthbreeding season was 78 per cent of the urban putrescible waste landfill reported in Ballarat, where ibis were thought to forage at Coalt. An urban colony near a mid-breeding a nearbywaste landfill (Kentish 1999).Lowe (1984) and in south-east Queensland was abandoned to wastethrough Bielharz (1988) reportedmuch higher fledging successand seasonwhen birds were preventedaccess pers. Dispersal breedingproductivity at Healesvillethan at other Victorian a program of disturbance(P. Shaw, obs.). scaring colonies,which was attributedto the constantfood supply of ibis from waste landfills using a range of bird in south-east at the nearby waste landfill. Australian White Ibis are techniquesis employed at least three landfills food on an opportunisticforagers and scavengeon human food waste Queensland in order to reduce access to in a variety of urban environments, including waste ongoing basis(Shaw and Murray 2004).At Ballina Landfill landfills, urban parks and gardens,and remnant wetlands (north-eastNew South Wales),complete physical exclusion (Marchant and Higgins 1990; Ross 2004). Therefore, of birds from the landfill was achieved through the variation in the timing and breeding successof Australian constructionof a permanentnet, which was erectedover White Ibis is likely influencedby differencesin abundance the entire active cell (Shaw and Patrick 2005). Despite and consistencyof food resources. sienificant costs involved, numbers of ibis reported June.2006 N. J. Mumy and P P Sharv;Breeding biology of the AustralianWhite lbis 45

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