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DDeakin Research Online Research Online This is the published version: Stojanovic, Dejan, Maguire, Grainne, Weston, Michael A., Dickman, Chris and Crowther, Mathew S. 2009, Attempted incubation and nest-maintenance behaviour of artificially deployed quail egg clutches by Hooded Plovers Thinornis rubricollis, International wader studies / Wader Study Group Bulletin, vol. 116, no. 1, pp. 41-43. Available from Deakin Research Online: http://hdl.handle.net/10536/DRO/DU:30022597 Reproduced with the kind permission of the copyright owner. Copyright : 2009, National Centre for Ornithology, International Wader Study Group

41Short communications

Usui 1985), it quickly became clear that the characters fitted well with non-breeding Grey-headed Lapwing. Most of the birds were in adult non-breeding plumage; only one lacked a blackish breast-band indicating that it was a juvenile.

The Grey-headed Lapwing was first recorded in Indo-nesia at Gorontalo (N Sulawesi) in 1869 (Andrew 1992, Sukmantoro et al. 2008, White & Bruce 1986), but it has not been found in N Sulawesi in recent surveys (e.g. Bororing et al. 2000, Riley 1997, Tebb et al. 2008).

Our record on 31 Dec 2008 in Aceh province, Sumatra, is not only the second record for Indonesia, but the first record for Western Indonesia (i.e. Sumatra, Kalimantan, Java and Bali). The site is at least 1,200 km south of the main non-breeding range in SE Asia and the circumstances that may have given rise to our observation are not clear. The latest reported trend for the species is one of decline, though that assessment was made as long ago as 1994 (Perennou et al. 1994, Wetlands International 2006). Moreover, as far as we are aware, there is no evidence of range expansion. Vagrancy over large distances normally involves individuals so it is a mystery why 20 Grey-headed Lapwings should have flown so far to the south of their normal range.

Our observation of Grey-headed Lapwings was made during fieldwork on an assessment of the population of the Milky Stork Mycteria cinerea in Sumatra supported by a Rufford Small Grant, the Wildlife Conservation Society Research Fellowship Program and Idea Wild. We wish to thank Dr Mike Crosby, Dr Christian Gonner, Yus Rusila Noor, Dr Dewi Prawiradilaga, Dr Nick Brickle, Dr William Banham, Kate Mastro, Lynn Duda, Jane Rufford, Josh Ruf-ford, Dr Wally van Sickle, Henry Stephen, Anne Marie and Sean Kelly who made this work is possible. We are grate-ful to Taej Mundkur for comments on an earlier draft and Humphrey Sitters for the final edited version.

Andrew, P. 1992. The Birds of Indonesia. A Checklist (Peter’s Sequences). The Indonesian Ornithological Society, Jakarta.

Bamford, M., D. Watkins, W. Bancroft, G. Tischler & J. Wahl. 2008. Migratory Shorebirds of the East Asian–Australasian Flyway; Population Estimates and Internationally Important Sites. Wetlands International-Oceania, Canberra, Australia.

Bororing, R.F., I. Hunowu, Y. Hunowu, E. Manaesa, J. Mole, M.H. Nusalawo, F.S. Tangalamin & M.F. Wangko. 2000. Birds of the Monembonembo Nature Reserve, North Sulawesi. Kukila 11: 58–70.

Coates, B. & K. Bishop. 2000. Burung-burung di kawasan Wallacea. Dove Publication/BirdLife International Indonesia Programme.

Hayman, P., J. Marchant & T. Prater. 1986. Shorebirds – an Identification Guide to the Waders of the World. Houghton Mifflin Company, USA.

King, B., M. Woodcock & E.C. Dickinson. 1975. A Field Guide to the Birds of South-East Asia. Collins, London.

Mackinnon, J., K. Phillips & B.V. Balen. 1998. Burung-burung di Sumatera, Kalimantan, Jawa dan Bali. BirdLife International Indonesia. Programme Puslitbang Biologi LIPI, Bogor.

Perennou, C.P., T. Mundkur & D.A. Scott. 1994. The Asian Waterfowl Census 1987–1991: distribution and status of Asian waterfowl. IWRB Spec. Publ. No. 24, AWB Spec. Publ. 86. Slimbridge, UK and Kuala Lumpur, Malaysia.

Piersma, T. 1996. Charadriidae (Plovers). Pp. 384–442 In: J. del Hoyo., A. Elliot. & J. Sargatal (eds). Handbook of the Birds of the World. Vol. 3. Hoatzin to Auk. Lynx Editions, Barcelona.

Riley, J. 1997. The birds of Sangihe and Talaud, North Sulawesi. Kukila 9: 3–36.

Robson, C. 2005. Birds of South-east Asia. New Holland Publishers, UK. Sonobe, K. & S. Usui. (eds). 1993. A Field Guide to the Waterbirds of Asia.

Wild Bird Society of Japan, Tokyo.Sukmantoro, W., M. Irham, W. Novarino, F. Hasudungan, N. Kemp & M.

Muchtar. 2008. Daftar Burung Indonesia No. 2. The Indonesian Ornitholo-gist’s Union/LIPI/OBC Smythies Fund/Gibbon Foundation, Bogor.

Tebb, G., P. Morris & P. Los. 2008. New and interesting bird records from Sulawesi and Halmahera, Indonesia. BirdingAsia 10: 67–76.

Wetlands International. 2006. Waterbird population estimates – Fourth edition. Wetland International, Wageningen, The Netherlands.

White, C.M.N. & M.D. Bruce. 1986. The Birds of Wallacea (Sulawesi, the Mollucas & Lesser Sunda Islands, Indonesia): An Annotated Checklist. BOU Checklist No. 7, Tring, UK.

Attempted incubation and nest-maintenance behaviour of artificially deployed quail egg clutches by Hooded Plovers Thinornis rubricollis

DEJAN STOJANOVIC1,2, GRAINNE MAGUIRE2, MICHAEL A. WESTON2,3, CHRISTOPHER R. DICKMAN1 & MATHEW S. CROWTHER1

1School of Biological Sciences, Building A08, University of Sydney, 2006, Australia d.stojanovic@birdsaustralia.com.au

2Birds Australia, 2-05 Green Building, 60 Leicester St, Carlton, 3052, Australia 3School of Life and Environmental Sciences, Faculty of Science and Technology, Deakin University,

221 Burwood Hwy, Burwood, 3125, Australia

Keywords: Hooded Plover, Thinornis rubricollis, nesting, incubation, egg recognition

Introduction

The Hooded Plover Thinornis rubricollis is a medium-sized shorebird endemic to southern Australia. The species occurs in two allopatric populations, with the eastern form being almost exclusively restricted to coastal habitats where it breeds above the high-tide mark on ocean beaches. Hooded Plovers rely on cryptic eggs and chicks for predator avoid-ance (Marchant & Higgins 1993). While there is substantial variation in the colour of Hooded Plover eggs, even within a clutch (Fig. 1), eggs are usually blotched tan and brown and

blend into the beach or dune sand on which they are laid. The simple nests are usually little more than a shallow depression in the sand above the high-tide mark (Marchant & Higgins 1993, Weston 2003). Although the eggs and chicks often go unnoticed by beach users, Hooded Plovers have low success during both the egg and chick phases owing to inadvertent anthropogenic disturbance and to depredation (Weston & Elgar 2007).

Here, we report Hooded Plovers attempting to incubate and care for quail eggs placed on beaches. We used quail eggs (from domesticated Japanese Quail Coturnix japonica)

42 Wader Study Group Bulletin 116 (1) 2009

as models for Hooded Plover eggs as part of a broader study aimed at examining whether conditioned taste aver-sion would reduce egg depredation by the red fox Vulpes vulpes. We conducted the study in February 2007, during the Hooded Plover breeding season and within the eastern geographical range of the species, along east/west running beaches close to Portland (38°23'31"S, 142°11'17"E) and Port Fairy (38°15'56"S, 141°41'10"E), Victoria, Australia. Commercially available quail eggs were selected because their size and colour resembles Hooded Plover eggs (Dodge et al. unpublished).

Thirty-six arrays of artificial nests were deployed at 1 km intervals along the coast. They were positioned above the high tide mark and monitored every second day over a period of 28 days. Each array contained two artificial nests (simple shallow scrapes in the sand which mimicked real nests), placed 5 m apart and each containing two quail eggs. We established a raked sand pad (a 1 m radius circle of flattened sand for recording footprints of animals visiting nests) around each array and monitored it every second day for footprints. Some quail eggs were sealed by the application of a wax cap at the blunt end of the egg to prevent leakage of its contents after manipulation for the conditioned taste aversion trials. This slightly modified the appearance of the eggs. Addition-ally, unmodified quail eggs were used to investigate whether the appearance of modified eggs influenced depredation by foxes and these arrays were deployed at least 10 km from the nearest modified eggs.

Observations

We regularly observed Hooded Plovers near the nest arrays, although we did not record any active Hooded Plover nests within 1 km of any array. Hooded Plover tracks were detected in sand pads on three occasions and Hooded Plovers were recorded on five occasions by video recorders positioned to monitor artificial nests, indicating approaches to the modified quail eggs as close as 2 cm. Hooded Plover tracks are distinct in size and shape from all other shorebirds known to occur at the study site.

In one instance, a pair of Hooded Plovers frequented an experimental array (at 38°23'31"S, 142°11'17"E) and began to “incubate” the eggs as though they were their own. This array contained unmodified quail eggs. Both members of the pair were observed digging well-defined nest scrapes around the quail eggs in each of two experimental arrays and both birds were observed “incubating” the quail eggs. Digging is a common behaviour at actual nests (M. Weston, personal observation 2007). Although no birds were banded, we assumed that the same individuals were involved in all observations because they exhibited the typical behaviours of breeding pairs and there were only ever two Hooded Plovers near this array. The pair was observed on 14 Feb 2007 from 15h00 until 17h00 and exhibited several behaviours typical of breeding pairs. These included changeovers and sharing incubation duties, leading (i.e. where one or both adults would run ahead of a perceived predator such as a human or dog, leading them away from the nest) and freezing (i.e. the incubating bird remaining motionless on the nest, often while its mate began leading behaviour away from the nest) (Marchant & Higgins 1993, Weston & Elgar 2007). At any time, only one bird was seen incubating a nest, thus there was always one unattended nest within the array.

Attendance at each nest in the experimental array seemed to depend on the direction of approach of the adult birds. If an incubating bird was disturbed from the nest and was

flushed to the east, on its return the bird would encounter the easternmost artificial nest first and would incubate those eggs. Conversely, when flushed to the west, the returning bird would encounter the westernmost nest first and would incubate that nest. Tracks in the sand pads surrounding each artificial nest in that array indicated that both had been subject to frequent visits from the birds, with many tracks leading to and away from the nests (Fig. 2).

When we discovered this behaviour, we moved the array at 19h30 on 14 Feb 2007 to a new location 100 m east due to concerns that we were inadvertently interfering with the breeding of this pair of Hooded Plovers. However, we failed to locate any real Hooded Plover nests in the area after thorough searching on the day of the initial observation and on the next three consecutive days. On 15 Feb 2007, at 07h20, a pair of unbanded Hooded Plovers (presumably the same pair) was observed in attendance at the new location of the array and a nesting scrape had again been constructed around each nest. The pair was observed until 09h20, and again exhibited typical nesting behaviour like freezing, lead-ing and nest maintenance. Although it is unknown if the birds involved in these observations were the same individuals, we presumed that the same pair was involved on both days of observation as there were no other Hooded Plovers recorded near the area on other days and breeding pairs maintain widely spaced territories on their breeding beaches (Weston 2005). After two hours of observation, the array was moved to another beach several kilometres away without any similar incident taking place.

Discussion

At several other arrays containing modified quail eggs in this experiment, we observed Hooded Plover tracks approaching very closely and then leading away again. The pattern of tracks around these eggs indicates that, although Hooded Plovers often encountered artificial nests containing modi-fied eggs during their breeding season, they were either able to discern that the eggs were abnormal or not their own, or alternatively, were not stimulated to perform behaviours such as incubation. The eggs, which were adopted by the Hooded Plover pair described here, were unmodified. There are regular reports of birds incubating inorganic objects such as pebbles and golf balls (Conover 1985, Coulter 1980, Guay et al. 2006) and Hooded Plovers incubate false eggs containing temperature probes (Weston & Elgar 2005). Further, Bryant (1936) reported Hooded Plovers trying to incubate the com-paratively large eggs of a Pied Oystercatcher Haematopus longirostris.

Two main hypotheses have been invoked to explain aber-rant incubation behaviour in birds: 1) adopting foreign eggs and pseudo eggs (inorganic, egg shaped items) increases re-productive fitness or 2) birds mistake a foreign or pseudo egg for their own egg (Conover 1985). Although some research has found that adoption may be an adaptive trait (e.g. Lank et al. 1991), other research has found it to be maladaptive for the adopting parents (e.g. Brown et al. 1995, Herbert 1987); in the present case, we cannot envisage a reproductive fitness benefit to the adoption of quail eggs. The experimental nest in this study never contained Hooded Plover eggs. Moreover attendance of the quail eggs by the plovers we observed not only had no reproductive benefit to the pair, but may have been a distraction from genuine breeding efforts.

It is also possible that the quail eggs were mistaken for Hooded Plover eggs by the birds involved. The ability for a bird to detect its own egg would seem to be a critical

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behavioural competency for the socially monogamous, dis-persed, territorial, Hooded Plover. This ability would seem adaptive in the following circumstances:

mAvoidance of the eggs of other species. A number of other beach-nesting birds nest in the same habitats and have similar cryptic eggs: Masked Lapwing Vanellus miles, Red-capped Plover Charadrius ruficapillus, Pied Oystercatcher, Little Tern Sterna albifrons and Fairy Tern S. nereis (Barrett et al. 2003, MAW pers. obs. 2007) all occur in the area.

mRelocation of eggs. Hooded Plover eggs can roll down dunes, up to several metres and eggs washed over by the tide can be transported along the shore for tens of metres (MAW pers. obs. 2007). Such displaced eggs have some-times been relocated and incubated by Hooded Plovers (MAW pers. obs. 2007, GM pers. obs. 2006–2008).

Behavioural mechanisms through which birds decide on the identity of eggs are poorly understood, and previous studies have mostly focused on species whose nests do not move during incubation. In species whose nests are parasitized, morphological characteristics of eggs are important in rec-ognition of egg identity (Lyon 2007, Rothstein 1975). It is possible that cryptic eggs offer few cues as to their identity and, given that the risk of predation far outweighs the appar-ently rare circumstance whereby “egg-confusion” occurs, it seems possible that the ability to identify eggs is of limited evolutionary significance to Hooded Plovers.

Our study focused on the use of quail eggs treated with a conditioned taste aversion (CTA) agent to develop a CTA among potential plover egg predators. If conservation actions for beach-nesting birds are to include the use of eggs containing a CTA agent, then it is pertinent to know how breeding Hooded Plovers respond to unattended egg-shaped objects in their breeding habitat. If our observations are not unusual and birds often attend deployed quail eggs, then this may limit the utility of using eggs to develop CTA as a conservation tool for shorebirds. The use of model eggs in trials on beaches is not novel (e.g. Rock Dove Columbia livia eggs, Buick & Paton 1989; quail eggs, Dodge et al. unpubl.) and is obviously preferable to the use of real eggs of a threatened species (Garnett & Crowley 2000). We sug-gest that further research determine the magnitude of any problem associated with the use of egg mimicks on beaches and that any further use of egg mimics be coupled with care-ful monitoring and management to minimize any impact to breeding shorebirds.

Acknowledgements

Our thanks go to Christopher Jackson, Cecilia Phu, Ric Ressom, Gus Stephens, Tijana Stojanovic and Erika Wagner for their assistance in the field trial; to Pamela Maguire for extracting data from the videos; to Dr Jim Gill for advice about our CTA agent. Thanks to the Sydney University Animal Ethics Committee and the Victorian Department of Sustainability and Environment for their approval and permits (AEC ref. No. L04/9-2006/1/4469; DSE license no. 10003945). Funding and support was also provided by Birds Australia’s Coexistence between Recreationists and Beach-nesting Birds Project funded by the Australian Governments Natural Heritage Trust via the Port Phillip and Westernport Catchment Management Authority. Our thanks go to Dr Bruce Lyon for his comments on the manuscript.

Barrett G., Silcocks, A., Barry S., Cunningham, R. & Poulter, R. 2004. The New Atlas of Australian Birds. Royal Australasian Ornithologists Union, Victoria.

Brown, K.M., Woulfe, M. & Morris, R.D. 1995. Patterns of adoption in Ring-billed Gulls: who is really winning the inter-generational conflict? Anim. Behav. 49: 321–331.

Bryant, C.E. 1936. The excursion to Marlo. Emu 35: 219–229.Buick, A.M. & Paton, D.C. 1989. Impact of off-road vehicles on the nesting

success of Hooded Plovers Charadrius rubricollis in the Coorong region of South Australia. Emu 89: 159–172.

Conover, M.R. 1985. Foreign objects in bird nests. Auk 102: 696–700.Coulter, M.C. 1980. Stones: an important stimulus for gulls and terns. Auk

97: 898–899.Dodge, F., Bunce, A. & Weston, M.A. In prep. Temporary beach closures for

breeding shorebirds on southern Australian beaches: compliance among recreationists, egg-crushing rates and optimal configuration. In prep.

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Guay, P.J., Gregurke, J. & Hall, C.G. 2006. A Black Swan incubating glass bottles. Aust. Field Ornith. 23: 50–52.

Herbert, P.N. 1987. Adoption behaviour by gulls: a new hypothesis. Ibis 130: 216–220.

Lank, D.B., Bousfield, M.A., Cooke, F. & Rockwell, R.F. 1991. Why do Snow Geese adopt eggs? Behav. Ecol. 2: 181–187.

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Weston, M.A. 2003. Managing the Hooded Plover in Victoria Parks. Victoria Technical Report 4.

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Fig. 2. Experimental array of quail eggs adopted by Hooded Plovers; note the Hooded Plover tracks surrounding the array, and the nesting scrape dug around the eggs.

Fig. 1. Natural variation in colour within a clutch of Hooded Plovers; note also the simple shallow scrape that constitutes a nest in this species.