Movements of a nomadic waterfowl, Grey Teal gracilis, across inland – results from satellite telemetry spanning fifteen months

D.A. Roshier1,*, N.I. Klomp1 & M. Asmus1

Roshier D.A., Klomp N.I. & Asmus M. 2006. Movements of a nomadic waterfowl, Grey Teal Anas gracilis, across inland Australia – results from satellite telemetry spanning fifteen months. Ardea 94(3): 461–475.

We used lightweight satellite transmitters to follow the movements of 17 Grey Teal Anas gracilis between September 2003 and November 2004 in two contrasting landscapes, the agricultural districts of southern Australia and the desert landscapes of the interior. Tagged moved large dis- tances (up to 343 km) between occupied sites in a short period (hours), remained in the vicinity of those sites for extended periods (months), ven- tured up to 453 km from their point of release and travelled more than 2000 km in one year. We describe patterns of movement in a nomadic waterfowl for 15 months from September 2003, a period of severe drought. Based on the current analysis there appears to be no remarkable difference in the observed patterns of movement of those released in the agricultural landscapes and those released in the desert. As in waterfowl elsewhere, movements appear to occur in response to changes in local food abundance that threaten survival or the imperative to move in order to breed successfully. In Grey Teal, the proximate cues for movement transcend the local landscape and some birds are responding to temporary cues hundreds of kilometres distant. This is in contrast to the universal seasonal cues associated with migration systems else- where.

Key words: arid environments, capital breeding, migration and moon phase

1Institute of Land, Water & Society, Charles Sturt University, P.O. Box 789, Albury 2640 Australia; *corresponding author ([email protected])

INTRODUCTION on long-distance seasonal migrants or seabirds that range over vast tracts of ocean but are The nature and extent of movements of nomadic philopatric to breeding location (e.g. Berthold et species remain enigmatic due to our inability to al. 1992, 1995, Meyburg & Lobkov 1994, Nicholls observe individual birds repeatedly or follow their et al. 1995, Walker et al. 1995, Davis et al. 1996, movements in real-time. Satellite telemetry is now Hake et al. 2001, 2003, Beekman et al. 2002, commonly used to track the movements of birds – Clausen et al. 2003, Fox et al. 2003; but see Petrie providing new insights into their movement pat- & Rogers 1997). Nomadic species respond to terns, migration routes, wintering sites and forag- changes in resource distribution that vary on other ing strategies. Most telemetry studies have been than annual cycles and patterns of movement are 462 ARDEA 94(3), 2006

considerably more variable than the north-south Lack of understanding of movements also lim- movements observed in many northern temperate its our understanding of the dynamics of Austra- long-distance migrants. lian waterfowl populations in time and space. The In Australia, evidence suggests that most scattered distribution of water across an otherwise waterbirds interact with available habitat at broad hostile landscape imposes a spatial structure on scales (Kingsford & Norman 2002; see Marchant & waterbird populations that may limit the move- Higgins 1990) and many respond quickly to ment of individuals within or between sub-popula- changes in distribution due to flooding tions for extended periods (years). However, it is and inundation of temporary lakes (Minton et al. likely that most constraints imposed by the spatial 1995, Kingsford et al. 1999, Alcorn & Alcorn 2000, distribution of are temporary and the iso- Roshier et al. 2002). The distribution and extent of lation of individuals and sub-populations is allevi- wetlands across inland Australia is at times vast ated by the mobility and dispersal capabilities of but virtually all are temporary (Roshier et al. many species (see Frith, 1957, 1959, 1962, 1963, 2001), necessitating the need for the birds that use Lawler et al. 1993, Minton et al. 1995, Kingsford them to move to survive and reproduce. Depend- 1996). What is unclear is the nature and extent of ing on the of movement used, these those movements and the physiological factors movements could be described as nomadic (Nix constraining them. 1976, Ford 1989, Griffioen & Clarke 2002), rang- In this paper we use satellite telemetry to ing (Dingle 1996), migration, or more simply non- examine the movements of Grey Teal across the sedentariness (Roshier & Reid 2003). desert landscapes of the Lake Eyre Basin and the The broad-scale movement patterns of many agricultural landscapes of the Riverina in southern Australian birds are poorly understood, particu- NSW. Dingle (1996) used the Grey Teal as an larly the movements of birds into, within and exemplar of what he described as ‘ranging’ behav- across the arid inland of the continent (Griffioen & iour, where an individual exploring an area seek- Clarke 2002). The movement of waterfowl into ing feeding and/or breeding habitat would cease and out of the arid interior of the continent and movement once suitable habitat was encountered. the significance of wetlands there to the mainte- This is in contrast to ‘migration’ during which nance of the broader waterfowl population has movement between breeding and non-breeding received increasing interest in the last decade or so ranges is undistracted and responses to resources (Lawler & Briggs 1991, Maher & Braithwaite are temporally suspended or suppressed (Dingle 1992, Lawler et al. 1993, Kingsford & Porter 1993, 1996). In this first contribution from an ongoing 1994, 1999, Halse et al. 1998, Kingsford 1996, study, we describe patterns of movement in a Kingsford et al. 1999, Roshier et al. 2001, 2002). nomadic waterfowl species, the Grey Teal, and To date, the only direct evidence of movement of interpret those movements in relation to existing waterfowl between the arid inland and more mesic models of movement and migration. areas comes from banding studies, although the data are few. Of the thousands of birds ringed by Frith (1957, 1959, 1962, 1963) at Griffith in METHODS southern NSW and elsewhere, a few bands were recovered in the arid zone, indicating movement We used lightweight (<20 g) satellite transmitters into that region. Lawler et al. (1993) ringed 746 to follow the movements of 17 Grey Teal in two Grey Teal Anas gracilis at Lake Altiboulka in the contrasting landscapes, the agricultural landscapes arid northwestern corner of NSW. All 19 recovered of the Riverina region of southern New South rings were from birds shot in southern NSW and Wales (n = 9) and the arid landscapes of the Lake South Australia demonstrating movement the Eyre Basin (n = 8), in the period between Septem- other way. ber 2003 and November 2004. Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 463

Study areas produce a diverse range of highly productive but The Riverina is a broad flat region in the southern mostly ephemeral wetland habitats for waterbirds part of the Murray-Darling Basin bisected by the and other biota (Puckridge 1998, Sheldon et al. Murrumbidgee River and bounded by the Murray 2002, Bunn et al. 2003). River to the south. Both river valleys have a long history of irrigation development and are the most Tracking of Grey Teal developed rivers in Australia (Kingsford 2000), Grey Teal are wide ranging and dispersive over with water diverted for the production of rice, most of the Australian continent and are only grains, vegetables, citrus, grapes and pasture. The absent from the driest regions of the great deserts region has hot, dry summers and cool, damp win- of the western half of the continent (Fig. 1). Grey ters. Mean annual rainfall declines westward Teal use a wide range of aquatic habitats but most across the region from c. 400 mm in the east to c. favour large, often temporary, shallow inland wet- 300 mm in the west. The most significant wet- lands that provide an abundance of aquatic vege- lands in the region are the Lowbidgee wetlands at tation and for a limited period the confluence of the Lachlan and Murrumbidgee (Marchant & Higgins 1990 and references Rivers, Fivebough Swamp and the Barmah Forest therein). Birds were caught using funnel traps on the Murray River. The Lowbidgee wetlands baited with grain (McNally & Falconer 1953) at include an area of 15 000 ha of Common Reed two locations in southern NSW, Fivebough Swamp Phragmites australis, Cumbungi Typha spp., River (34.53°S, 146.44°E) near Leeton and Barrenbox Red Gum Eucalyptus camaldulensis and rush Swamp (34.13°S, 145.86°E) near Griffith, and at Eleocharis spp. and Juncus spp. (Macgrath 1992). Lake Hope (28.38°S, 139.25°E) c. 1000 km to the Fivebough Swamp is a large (400 ha) natural northwest in northern South Australia (Fig. 1). depression with managed water levels in the midst Only adult birds weighing c. 500 g or more were of agricultural enterprises that is listed as a fitted with a transmitter and harness. All birds Ramsar site and ‘Wetland of national importance’ were released at their point of capture. (Environment Australia 2001). The Barmah- Two types of satellite transmitters were Millewa Forest is 65 000 ha in area and is the deployed: four transmitters had batteries that were largest river Red Gum forest in Australia (Kings- solar-enhanced (Microwave Pico PTT) and 13 did ford 2000). not (Northstar Solar PTT). Transmitters were The Lake Eyre Basin is a vast (1 140 000 km2) attached to the back of each bird by a harness internally draining basin of varied landscapes of comprising a neck loop and a body loop of 6 mm longitudinal sand dunes, hard gibber (stony) Teflon ribbon (Bally Ribbon Company, P/L). The plains, large salt lakes, and broad floodplains asso- harness design was a modification of earlier ciated with dryland rivers that flow south and designs by Bander (1968). Our design is different west down shallow gradients toward terminal wet- to that of traditional harness arrangements in that lands 100s kilometres to the south (see Puckridge the neck loop and breast section are perpendicular 1998). Northern parts of the basin extend into the to the body loop to form a T-intersection. On the tropics and receive rainfall runoff most years bird this arrangement holds the body loop poste- (Roshier et al. 2001), while the southern part is rior to the wings and prevents feather and skin the driest region on the continent (c. 100 mm abrasion where the trailing edge of the wing meets mean annual rainfall). As a result of the shallow the body. Ribbon was passed through the attach- gradients, flow velocities of flood waters down ment lugs and secured using crimps (180–227 kg, these catchments are low (Kotwicki 1986) and Osaka Tackle, Japan) re-sized to 0.5 cm in length. flood transmission times are long (Knighton & Crimps were compressed onto the ribbon with a Nanson 1994). The infrequent floods inundate Jinkai® crimping tool and a small amount of super- vast areas (106 ha; Roshier et al. 2001) and glue applied to the ends of the trimmed ribbon to 464 ARDEA 94(3), 2006

1000 km range breeding range

Figure 1. Map showing geographic range and breeding range of Grey Teal (after Marchant and Higgins 1990) and the location of release sites in the agricultural districts of the southern Murray-Darling Basin and the Strzelecki Desert in the Lake Eyre Basin. The two major drainage basins of eastern and central Australia are outlined. prevent fraying. The weight of each transmitter ble fixes among those that remained using exclu- with harness was c. 20 g, representing 4% or less sion rules (D.C. Douglas unpubl. method; see of the body mass of the Teal (mean 554 g). Kenow et al. 2002). Locations were retained based The locations of the birds were determined on the rate of movement between location fixes, from location fixes supplied by satellites via the the angle of movement in relation to adjacent fixes CLS-ARGOS service (Argos 1996). All transmitters and proximity to previous and subsequent loca- were programmed to run on a duty cycle, either 7 tions. In effect LC 0 fixes were only retained when h on / 17 h off (Northstar units) or 10 h on / 24 h their position was consistent with the direction of off (Microwave units) to take advantage of the travel on longer flights or their position was sup- Limited Use Service for biological researchers on ported by other fixes. the CLS-ARGOS system. The calculated positions are assigned a nominal locational accuracy, loca- tion class 3 (<150 m), 2 (150–350 m), 1 (350– RESULTS 1000 m) or 0 (>1000 m). Location classes A, B and Z are calculated from fewer than four pulses Patterns of movement or are fixes that can not be assigned an accuracy Patterns of movement varied markedly between because they have failed one or other parity test. individuals in both the Riverina and the Lake Eyre The number of fixes per day from any single trans- Basin groups in terms of direction taken and dis- mitter can be as many as 10 but more typically the tance moved (Table 1). From the point of release number of fixes is two to four per day. The data birds dispersed in many directions, often undertak- were filtered to remove all poor position fixes (i.e. ing long flights between locations that may be ARGOS location classes A, B and Z) and implausi- occupied for months (Figs 2 and 3). Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 465 ns. 94 118 a 194 62 10.9 14.4 290 a a b 21 106 279 91 89 397 a a Several months without location data. b 2.9 8.4 5.1 25.2 3.0 4.7 7.6 10.1 7.2 13.7 12.7 7.7 5.1 9.9 na ) ) –1 –1 Summary of movement data from deployment till 26/11/04 collected from Grey Teal fitted with satellite transmitters in two regio Teal Grey deployment till 26/11/04 collected from Summary of movement data from Eyre Basin Eyre ght (g) 520 540 540 515 515 510 495 590 545 ght (g) 590 585 560 600 650 555 600 580 ke ngest flight (km) 12 286 158 338 14 239 97 51 262 ngest flight (km) 44 195 343 181 140 151 306 106 ransmitters that were still functioning on 26/11/04. ransmitters that were able 1. otal distance travelled (km) 178 2395 2279 529 318 1313 2192 946 844 otal distance travelled (km) 549 2545 3046 461 883 2133 2115 890 otal days 61 286 451 otal days 40 201 396 T Lo T origin (km)Max. distance from Mean rate of movement (km day 24 288 215 332 22 243 96 243 338 Lo T origin (km)Max. distance from Mean rate of movement (km day 45 430 395 375 213 214 466 200 Date of deploymentLast date of transmissionT 17/06/04 20/04/04 22/06/04 10/09/03 26/11/04 2/09/03 01/03/04 10/02/04 04/08/04 20/04/04 25/11/04 20/02/04 26/11/04 10/02/04 24/05/04 20/02/04 24/05/04 10/02/04 T Riverina IDWei 40869 40871 40874 40875 40876a 45882 45883 45884 45885 La Date of deploymentLast date of transmissionT 05/12/03 27/10/03 15/05/04 27/10/03 26/11/04 27/10/03 26/01/04 27/10/03 23/01/04 26/10/03 26/11/04 27/10/03 07/05/04 27/10/03 27/12/03 26/10/03 IDWei 40870 40872 40873 40880 41420 41421 41422 41423 466 ARDEA 94(3), 2006

Of the nine birds released in the Riverina, six were Bird flights can be divided into short and long 200 km or more from the point of release at some trips. Short trips reflect foraging and other mainte- stage during 15 months of the study so far. The nance behaviours within a discrete area, typically a individual that has been tracked the longest wetland or group of wetlands, whilst long trips are (#40874, 451 days) travelled at least 2279 km those flights where the birds are flying between and ventured up to 215 km from the point of locations. The pattern of movement is strongly release in that time. Only two birds (#40875 and skewed with the vast majority of movements #45885) of the nine birds released in the Riverina between fixes over a short distance and a few over have travelled more than 300 km from their point markedly longer distances (Fig. 4). Most move- of release. By contrast, four of the eight birds ments were less than 5 km, being 78% and 83% of released in the Lake Eyre Basin travelled more all recorded movements in the Riverina and Lake than 300 km from their point of release and three Eyre Basin, respectively. There were 12 observed of the remaining four travelled more than 200 km flights of 100 km or more per day for which from their point of release. bounds could be placed on departure and arrival The mean rate of movement varied markedly times using all available locational fixes (Table 2). between individuals, ranging between 2.9 and The longest observed flight was 343 km in straight 25.2 km per day. The individual (#40869) that line distance (#40872). It is not possible to deter- had the lowest mean rate of movement was no mine with any certainty from these data whether more that 24 km from its point of release at longer flights occurred during daylight hours or at Fivebough Swamp in the 61 days it was tracked. night as most of the transmitters switch off after By contrast, the individual (#40875) with the operating for seven hours from first activation by greatest mean rate of movement remained on or sunlight in the early morning. If travelling at near its point of release at Barrenbox Swamp for night, there appears to be no consistent timing in 20 days before being taken by a raptor 332 km to relation to moon phase for these long flights, apart the north the following morning. This was the from the fact that all occurred between the start of longest single flight between consecutive fixes of the first quarter and the end of the last quarter – any of the Riverina group of birds (Table 1). none occurred on moonless nights (Table 2).

Table 2. Distance travelled, maximum travel time and phase of the moon corresponding with flights of greater than 100 kilometres per day.

Region ID Date and transmission times Distance Maximum travel Moon travelled (km) time (hours) phase

Riverina 40871 17/11/03 13:32 – 18/11/03 10:44 285 21.2 40875 29/02/04 12:19 – 01/03/04 06:20 338 18.0 45882 15/06/04 10:37 – 16/06/04 10:25 240 23.8 45885 09/03/04 10:05 – 10/03/04 08.01 262 21.9 Lake Eyre Basin 40872 21/11/03 12:49 – 22/11/03 05:44 197 16.9 07/01/04 11:01 – 08/01/04 06:32 111 19.5 30/04/04 10:22 – 01/05/04 11:00 139 24.6 40873 12/08/04 12:53 – 13/08/04 08:56 343 20.0 08/11/04 10:54 – 09/11/04 08:32 181 21.6 41422 16/01/04 23:39 – 18/01/04 07:42 293 32.1 15/03/04 14:33 – 16/03/04 21:28 297 30.9 41423 10/12/03 17:16 – 11/12/03 21:05 143 27.8 Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 467

350 Fivebough Swamp 40874* 40871 40876 300 40869

250

200

150

100 distance from origin (km) 50

0 Sep Nov Jan Mar May Jul Sep Nov 2003 2004

350 Barrenbox Swamp 40875 45882* 45883* 300 45884 45885 250

200

150

100 distance from origin (km) 50

0 Feb Apr Jun Aug Oct Dec 2003

Figure 2. Distance from origin through time of tagged birds released in the Riverina.

As with the direction of movement away from months in the Barmah Forest (200 km to the the point of release, the rate and nature of move- southeast) in the same approximate location, sug- ment also varied. Of the six birds in the Riverina gesting that it bred. The other (#40871), flew 285 that moved more than 200 km from the point of km overnight to a sewerage treatment works at release, five did so in one or two long flights of Swan Hill on the Murray River (Fig. 3). In June 100 km or more (Fig. 2). Only one bird moved 2004, both birds moved back to the large regu- away from the point of release (#45844) in a lated wetlands in the irrigation district where they series of smaller flights of 30–50 km in length to tagged – one (#40871) remained in the district be 242 km from the point of release after 94 days and was shot in August, while #40874 again (Fig. 2). Two birds (#40871, #40874) returned to moved hundreds of kilometres out of the irrigation the location they were trapped on at least one district onto small natural and roadside wetlands. occasion during the course of the study, having On returning in August to Fivebough Swamp for travelled many tens or hundreds of kilometres in the fourth time, this bird remained at the swamp the meantime (Fig. 3). One (#40874) spent five for the next three months. Other birds released in 468 ARDEA 94(3), 2006

Figure 3. Movement paths of two Grey Teal released in the Riverina #40871 (top) and #40874 (bottom). The shaded areas indicate regions were the dominant landuse is irrigated agriculture and grey lines are drainage features. Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 469

500 Lake Hope 40873* 41421* 41422 40872 400

300

200

distance from origin (km) 100

0 Nov Jan Mar May Jul Sep Nov 2003 2004

Figure 4. Distance from origin through time of tagged birds released in the Lake Eyre Basin. Asterisk denotes trans- mitter still operating in November 2004. the Riverina have not shown the same tendency to satellite data show that Lake Hope was dry by late return to the location they had been trapped and November 2003 but inundated again by February tagged. Three (#40875, #45885, #45882) flew 2004 (unpubl. data). hundreds of kilometres overnight to locations out- Despite the almost synchronous departure of side the region and remained at the new location birds from Lake Hope in late November 2003 (Fig. for extended periods (months), while two (#40876 4) their subsequent movement responses differed & #40869) remained in the area where they had markedly. One bird (#40873) remained within 80 been tagged and released. Another bird (#45883) km of Lake Hope on shallow temporary wetlands released from Barrenbox Swamp moved to for nearly 10 months before moving 357 km to the Fivebough Swamp in early September 2004 having south to a region with no known significant wet- spent the intervening six months on the mid- lands. This bird remained at that location for seven Murrumbidgee (34.42°S, 145.02°E) near Hay. weeks before moving north towards Lake Frome In contrast to birds released in the Riverina, and departing four weeks later on 9/11/04 for the those released in the Lake Eyre Basin mostly western shore of Lake Torrens (a large salt lake stayed away once they had moved away from the that last filled in 1989, c. 180 km to the west). By point of release (Fig. 4). One bird (#41423) contrast #41422 flew to Malcho Creek (25.91°S, departed Lake Hope on 2/11/03 for Andracunie 142.56°E) near Windorah in south-west Queens- Swamp (27.46°S, 139.49°E), 104 km to the north, land, 427 km to the northeast on 17/01/04 to returning to Lake Hope five days later and then meet floodwaters moving down Cooper Creek departing again on 22/11/03 for small wetlands (Fig. 5). Its previous location had been on Cooper 57 km to the west. Andracunie Swamp retained Creek west of Innamincka township in South open water throughout the summer of 2003/04 Australia. On the floodwaters reaching that part of and was one of the few wetlands to do so in the the Cooper Creek system in late February (unpubl. region. Another bird (#41422) departed Lake data) this bird returned to it’s previous location on Hope on 14/11/03, while the remaining seven 18/03/04 – two months after departing, a round departed on 22/11/03 (#41420, #41423, trip of c.1100 km. In contrast to the long-distance #41421, #40872 and #40880), 23/11/04 flights of some individuals, #40870 departed Lake (#40870) and 25/11/03 (#40873). Analyses of Hope on 23/11/03 returned on 2/12/03 for a day, 470 ARDEA 94(3), 2006

Figure 5. Movement paths of Grey Teal released on the 26/27th October 2003 at Lake Hope in the Lake Eyre Basin. having spent time on shallow temporary lakes that know from the odd banded Grey Teal that crossed form between the sand dunes after rain, and died the Australian continent (Frith 1959). The insight on 6/12/04 c. 40 km to the northwest in the dune gained from this study is that long-distance move- fields of the Strzelecki Desert. The transmitter ments vary markedly at the individual level in from this bird was recovered in June 2004 and terms of timing and/or direction, and that the showed no sign that the bird had been predated as movements of this so-called nomadic species do the harness was complete and the transmitter still not appear to be random wanderings between working. adjacent wetlands. Many birds moved a large dis- tance (up to 343 km) between occupied sites in a short period (hours), remained in the vicinity of DISCUSSION those sites for extended periods (months), ven- tured up to 466 km from their point of release and Patterns of movement travelled more than 2000 km in a year (Fig. 6). The observed flights of Grey Teal are not extraordi- Based on the current analysis there appears to be nary in terms of distance or rate of movement no remarkable difference in the observed patterns when compared to many species of waterfowl that of movement of those released in the agricultural undertake long-distance seasonal migration in landscapes of the Riverina and those released in northern temperate regions or what we already the desert landscapes of the Lake Eyre Basin. Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 471

1900 Riverina Lake Eyre Basin

1700

1500

30 frequency

20

10

0 0 50100 150 200 250 300 350 distance between fixes (km)

Figure 6. Histogram of flight lengths based on distance between consecutive location fixes of all birds released in the Riverina and the Lake Eyre Basin. In addition there were three flights in the Lake Eyre Basin greater than 600 km.

The observed patterns of movement of Grey desert regions and the more mesic agricultural dis- Teal in this study contrast to the movement pat- tricts. terns observed in White-faced Whistling The observed pattern of movement suggests Dendrocygna viduata (Petrie & Rogers 1997) – the that Grey Teal interact with available habitat at only other telemetry study of waterfowl in a semi- broad scales and that movement at these scales is, arid environment. In a study of two individuals in at least in part, based on experience and spatial South Africa, the maximum distance moved by a memory (see Benhamou & Poucet 1996, Benha- White-faced Whistling Duck from the point of mou 1997, Bingman & Able 2002, Benhamou et al. release was 82 km in a 226 day study period as 2003, Lipp et al. 2004, and references therein). birds moved between a well watered agricultural Some tagged individuals moved large distances district utilised in winter and an infrequently between wetlands, reaches and catchments over flooded breeding habitat (Petrie & Rogers 1997). regions with a multitude of other natural and man- In the current study, individuals moved markedly made wetland resources, to settle on small wet- larger distances between occupied sites, even lands or in regions with few significant wetland those birds occupying a well watered agricultural resources. For instance, #40871 travelled 280 km landscape. Petrie & Rogers (1997) suggested that overnight across the Riverina to settle on a sewer- a portion of the White-faced Whistling Duck popu- age treatment works, apparently ignoring numer- lation have adjusted their movement patterns to ous flooded rice bays and other wetland resources the post-European settlement distribution of crop- along the way. Similarly, #45882 moved 240 km ping and water resources. There is no evidence in overnight from Barrenbox Swamp to an area of this study to date to suggest that Grey Teal have few natural wetlands. Once arriving at a new loca- similarly modified their movement patterns as tion, individuals have spent periods of six months individuals moved away from areas of intense or more in the same general vicinity. This pattern agricultural development of water resources to of movement may reflect breeding activity and/or areas with few significant water resources. previous patterns of habitat occupancy. That Nonetheless, some individuals utilised agricultural #40874 returned to Fivebough Swamp, the point infrastructure such as ground tanks in both the of release, on three occasions suggests previous 472 ARDEA 94(3), 2006

patterns of habitat occupancy play a significant It has been suggested that waterbirds in arid role in determining the movement patterns of this environments find temporary wetlands by visual species. Similar return flights over long distances cues such as cloud formation (Simmons et al. were observed in #41422 when this bird returned 1998). While this could explain some movements to its previously occupied habitats on Cooper Creek it does not explain overnight movements of hun- soon after the area was flooded in early 2004. dreds of kilometres to intercept flood waters flow- In contrast to the birds released in the ing down dryland rivers or long-distance move- Riverina, all eight birds tagged at Lake Hope in the ments to isolated wetlands in an otherwise hostile Lake Eyre Basin in late October 2003 were forced landscape. The observed movements of tagged to move due to the lake drying. The almost syn- birds in this study occurred during a period of chronous departure of tagged birds in late extended drought (the worst since records started November 2003 suggests that the 40 000+ water- in the1850s) with few obvious weather cues to ini- fowl observed at the lake in October continued to tiate movement. Simmons et al. (1998) further exploit the food resources of the lake until they suggested that changes in temperature and pres- were depleted. The subsequent fate of tagged indi- sure gradients may play a role in waterbirds find- viduals suggests that experience and spatial mem- ing temporary wetlands. This could not be the ory play a part in survival in such extreme circum- case except for local movements as floodwaters in stances. The apparent prospecting flight of one inland Australia can take months to reach the bird (#41423) to Andracunie Swamp and its sub- lower catchment – long after the weather signal sequent movement to Goyders Lagoon contrast that produced the flooding has dissipated. For with the ill-fated movements of another (#40870) waterbirds to find these waters there must be onto temporary wetlands in the dune fields of the other cues. In a recent review Wallraff (2004) Strzelecki Desert and its subsequent return to an argued that evidence for olfactory navigation in almost dry Lake Hope. birds was conclusive in the affirmative, even if the atmospheric compounds on which they were cue- Proximate cues for movement ing remain unknown. Olfactory navigation as a In contrast to northern temperate environments means for waterbirds to find wetland habitat is where daylength and temperature changes are intuitively appealing as it can operate at finer obvious proximate cues for movement to breeding scales than other avian navigation methods that habitats, the cues for movement used by birds in rely on geomagnetism, solar or celestial orienta- an stochastic environment are less obvious. tion or infrasound (see Alerstam 1990, Dingle Approximately 40% of the Australian avifauna 1996). Indeed it would seem likely that increases show some migratory behaviour, although migra- of several orders of magnitude in primary produc- tory movements vary greatly within and between tivity by algae and other micro-organisms on a species and populations (Chan 2001, and refer- recently inundated floodplain (see Bunn et al. ences therein). As for many northern temperate 2003) would produce a distinctive olfactory signa- species, this behaviour is in part under endoge- ture compared to that produced during a dry nous control and some species exhibit migratory period. What that signature could be can only be restlessness, adjustments to orientation and weight speculated upon but may be analogous to the smell gain (Munro 2003). Similarly, there is some sea- of rain on dry soil signalling an approaching storm. sonality in the timing of breeding in Australian waterfowl, albeit over a greater range of dates The ecological context of observed movements than northern temperate species (Briggs 1992). In long-distance seasonal migrants we can readily However, seasonal movements do not explain how distinguish between maintenance movements waterbirds find temporary waters and suitable (sensu Roshier & Reid 2003) undertaken to meet breeding habitat on a vast arid continent. the individual’s immediate and short-term needs Roshier et al.: MOVEMENTS OF NOMADIC GREY TEAL 473

and migration because they occur on markedly dif- not. Understanding those constraints in a stochas- ferent spatial and temporal scales. In dynamic tic environment where patterns of resource distrib- landscapes where changes in the distribution of ution vary will inform us how other species might resources is a broad scale stochastic process the respond to disturbances such as those anticipated distinction is not so evident as both types of move- due to climate change. ment can occur over large geographic distances (Dingle 1996, Roshier & Reid 2003). In this study, movements of tens to hundreds of kilometres ACKNOWLEDGEMENTS could be characterised as occurring in response to the need to move to survive or travelling to breed, We gratefully acknowledge Mike Schultz for his time and depending on the distribution of wetland habitat invaluable knowledge in the field, and the Fivebough and at the time. To distinguish between these behav- Tuckerbill Wetlands Management Trust. We also thank iours much more needs to be known about the Wagga Wagga City Council, specifically Tony Smith of Wagga Wagga Botanical Gardens, John Smith for facilita- cues for movement and the constraints associated ting trials of harness designs on captive birds, Richard with moving large distances across an arid land- Page and Jess Newton collecting behavioural data, Tobi scape or for initiating breeding. At least one arid Edmonds for monitoring and statistical analysis and zone waterfowl species, the White-faced Whistling Mark Wilson for field assistance. Special thanks to Tony Duck, is a capital breeder – utilising endogenous Agnew and George Townsend (South Australia Parks), Ross McDonnell (NPWS Griffith) and Garry Overton fat stores for clutch formation (Petrie & Rogers (Mulka Station). We also thank Marcel Klaassen, Bart 2004). Waterbirds utilising temporary wetland Nolet and other members of the Plant– Inter- habitats in arid environments for breeding are actions group at the Institute for Ecology for time constrained as evaporation and prey dynam- discussions that helped clarify ideas on avian migration ics combine to limit the time for which prey items systems. This project was undertaken under NSW are available to feed young. Storage of fat prior to National Parks and Wildlife Scientific Licence numbers S10426 and 3244, South Australian Scientific Licence arrival at breeding sites reduces ‘reproductive number U24666, South Australian Animal Care and uncertainty’ associated with utilising time-limited Ethics Approval number 118, Charles Sturt University resources (Petrie & Rogers 2004). Australian Animal Care and Ethics Approval No. 01/061 and funded waterfowl may use a similar strategy, although by the New South Wales National Parks and Wildlife carrying additional fat reserves may then constrain Service, Rural Industries Research and Development movement as in long-distance migrants (see Corporation, Game Bird Management Committee and Australian Research Council. Lindström 2003 and references therein). The movements of Grey Teal observed in this study are analogous to those observed elsewhere in waterfowl in that they appear to occur in REFERENCES response to changes in local food abundance that threaten survival or the imperative to move in Alcorn M. & Alcorn R. 2000. Seasonal migration of order to breed successfully. It is not yet clear Banded Stilt Cladorrhynchus leucocephalus to the Natimuk-Douglas salt pans in western Victoria, whether these movement responses are best Australia. Stilt 36: 7–10. described as ‘ranging’ or migration (sensu Dingle Alerstam T. 1990. Bird migration. Cambridge University 1996). However we can say that the proximate Press, Cambridge. cues for movement transcend the local landscape Argos CLS 1996. User’s manual. CLS Argos, Toulouse. and some birds are responding to temporary cues Bander R.B. 1968. A radio-package harness for game birds. J. Wildlife Manage. 60: 669–678. hundreds of kilometres distant. While the cues for Beekman J.H., Nolet B.A. & Klaassen M. 2002. Skipping movement certainly differ to those that prompt swans: fuelling rates and wind conditions determine migration in northern temperate species, the phys- differential use of migratory stopover sites of iological constraints on movement probably do bewick’s swans Cygnus bewickii. Ardea 90: 437–460. 474 ARDEA 94(3), 2006

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