Conserving Australia’s resident shorebirds

A project undertaken at The Deakin Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University and supervised by Dr Mike Weston

Many of Australia’s 18 species of resident shorebirds are in crisis, predominately because they nest on the ground where they experience low rates of reproduction due to high rates of egg depredation. One species, the Hooded Plover, has such poor breeding success, that only one pair in ten successfully raise young in any given year. There is a critical need, therefore, to identify which predators have the greatest impact on these birds, many of which are threatened. While predator identification is notoriously difficult, camera technology has recently become available which will revolutionize our ability to identify predators. This study used this IR motion-sensing camera technology and has enabled wildlife and conservation agencies to develop appropriate management strategies for both the predators (e.g., reducing numbers or through aversive conditioning), and shorebirds (e.g. predator-proof fencing around critical nesting areas). Hence, the aim of this study is to identify the main predators of ground-nesting shorebirds so that better conservation outcomes for these species can be achieved.

ACHIEVEMENTS

A series of honours and other student projects have been conducted as part of this project:

  • The first species studied was the ubiqitous Masked Lapwing Vanellus miles, on Phillip Island, Victoria. In 2010 Honours student Adam Cardilini placed cameras on randomly selected nests in rural and urban areas, to determinenest survival and fate (and yes, Adam was swooped!). Adam discovered that nest fates differed between urban and rural enviornments, with few predators but many human-induced nest lossesin urban areas, and predation and crushing by stock the main nest fates in rural areas. In fact, urban lapwings do better than their rural cousins in terms of reproductive success, a complete surprise, and the subject of a paper which is currently in preparation
  • Another honours student (Kasun Ekanayake) used cameras on false eggs and nests to show that ravens detect eggs by sight, while foxes use scent and also probably sight to detect eggs. He also showed that brightly coloured incubators were more prone to loosing their eggs to diurnal predators (like ravens) compared with duller incubators. Preliminary work on Red-capped Plovers Charadrius ruficapillus has revealed that ravens are responsible for over 80% of next losses, at Cheetham Wetlands, on the western side of Port Phillip Bay, Victoria.
  • Stephanie Lomas used cameras to index predators in a major breeding site of Red-capped Plovers during 2011/2012. She showed that 100% of nest takes were dues to Little Raven Corvus mellori (cameras were not used on real nests in case ravens had learned to key into cameras to find real nests, instead we used false nests and eggs). The study continued without cameras, and was run in parallel with an honours project by Kelly Shannon who radio-tracked and surveyed ravens, so that correlations between egg survival and raven behaviour and aubundance can be generated.
  • Renee Mead deployed cameras on Hooded Plover Thinornis rubricollis nests during the 2011/2012 breeding season, covering tens of thousands of kilometres in travel, and deploying cameras on over 60 nests. The ‘big three’ predators were foxes, ravens and magpies, though birds of prey and a water rat also took eggs. Extensive statistical modelling revealed that no habitat variables were associated with the chances of clutch success, which was about 50%.
  • A key feature of this study was developing conservation solutions. In 2011-2012, honours student Aimie Cribbin examined Conditioned Aversion as a method of reducing egg depredation. In Conditioned Aversion, eggs with aversive agents (i.e. those that make a predator ill) were used to attempt to train predators to avoid eating eggs. Unfortunately, the approach appears not to have worked, because of low predator-specificity of the training. However, Aimie showed that real Hooded Plovers were preferentially selecting nest sites in the open and away from grass i.e. circumstances where rodent take of eggs was unlinkely.
  • Hayley Glover deployed cameras in the Mackay area of Queensland , on Bush Stone Curlew Burhinus grallarius and Masked lapwing nests, as well as on a single Beach Stone Curlew Esacus magnirostris nest. This revelaed a take of eggs by wild dogs, interference by people, and close encounters with snakes.
SUMMARY

What have we learned? Those shorebirds we have sampled did not experience high rates of egg loss to rodents, and none to reptiles. This is probably because of the preference for nesting inopen areas. However, we found substantial differences betweeen regions. Most egg loss on Victorian beaches was due to ‘likley suspects’ (i.e. foxes) though ravens and magpies were also prominent predators. Urbanisation changed the mix of predators eating lapwing eggs in the virtually fox free Phillip Island.

THE FUTURE

A key goal of this project was to develop conservation solutions. Thus, work will continue. Plans are afoot to trial nest cages on Red-capped Plovers, and alternative management techniques for ravens. Magpies are also likely to be the subject of management intervention. None of this work would be possible without the ongoing support of HSF, and we thank the Foundation for its generous support.

PUBLICATIONS

Cardilini, A P A, Weston, M A, Nimmo, D G , Dann P and Sherman, C D H (2013). Surviving in sprawling suburbs: Surburban environments represent high quality breeding habitat for a widespread shorebird. Landscape and Urban Planning, 115, 72 - 80.

Tan, L.X.L., Buchanan, K.L., Maguire, G.S, and Weston, M.A. (2015). Cover, not caging, influences chronic physiological stress in a ground-nesting bird. Journal of Avian Biology, 46: 482-488.

Ekanayake, K.B., Weston, M.A., Nimmo, D.G., Maguire, G.G., Endler, J.A. and Küpper, C. (2015). The bright incubate at night: sexual dichromatism and adaptive incubation difvision in an open-nesting shorebird. Proc. R.Soc. B 282: 20143026. http://dx.doi.org/10.1098/rspb.2014.3026

Ekanayake, K.B., Whisson, D.A., Tan, L.X.L. and Weston, M.A. (2015). Intense predation of non-colonial, ground-nesting bird eggs by corvid and mammalian predators. Wildlife Research, 42, 518-528. http://dx.doi.org/10.1071/WR15080

Ekanayake, K.B., Sutherland, D.R., Dann, P. and Weston. M.A. (2015). Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins. Wildlife Research. http://dx.doi.org/10.1071/WR15108.

Cardilini, A.P.A., Weston. M.A., Dann, P. and Sherman, C.D.H. (2015). Sharing the load: Role equity in the incubation of a monomorphic shorebird, the Masked Lapwing (Vanellus miles). The Wilson Journal of Ornithology, 127(4): 730-733. DOI: http://dx.doi.org/10.1676/14-189
 

Figure 1. Adam installs a camera at a lapwing nest

Figure 2. A White-faced Heron passes by a Masked Lapwing nest. While this species is a potential predator of lapwing eggs, this bird ate a spider and left the nesting area.

Figure 3. A lapwing sits tight while sheep stand watching. Stock were attacked by lapwings, but they continued to inadventendly crush nests.

 

Figure 4. Not all bad news, the cameras also reliably detect hatching. This lapwing chick is about one day old.

 

Figure 5. An image of an incubating Hooded Plover, and a recently hatched chick, near Torquay, Victoria.