Predation of artificial ground nests in Australian tropical savannas: inverse edge effects
Fiona J. Fraser A C and Peter J. Whitehead BA Tropical Savannas Cooperative Research Centre and Parks and Wildlife Commission of the Northern Territory, Darwin, NT 0900, Australia; and Centre for Resources and Environmental Studies, Australian National University, Canberra, ACT 0200, Australia. Present address: Caring for Country Unit, Northern Land Council, PO Box 42921, Casuarina, NT 0811, Australia.
B Key Centre for Tropical Wildlife Management, Northern Territory University, Darwin, NT 0909, Australia.
C Corresponding author.
Wildlife Research 32(4) 313-319 https://doi.org/10.1071/WR04021
Submitted: 22 March 2004 Accepted: 19 April 2005 Published: 5 July 2005
Abstract
Depredation of artificial ground nests was examined in tropical savanna in northern Australia to assess potential predation pressures on nests of the partridge pigeon (Geophaps smithii), a declining tropical granivore. Predation rates were examined at two sites, Kakadu National Park (which supported a relatively high density of partridge pigeons) and Berry Springs (which had greater habitat fragmentation and comparatively low partridge pigeon density). The effects of distance from road, understorey structure, topography and nest-microsite concealment on nest predation rates were examined. Artificial-nest predation rates were greater at 150 m from roads than <1 m from the roadside. Predation rates did not vary with understorey structure, topography, or level of nest concealment. There was marked variation between sites, with predation levels at Kakadu more than double those recorded for Berry Springs. Discerning predator identity, or even the size of a predator, from marks left in clay eggs proved difficult and was possible for ~35% of predation events. Of these, 42% of predation events involved predators of a size we considered too small to take a natural partridge pigeon nest. We suggest that extrapolation from artificial to natural ground-nest predation rates be undertaken with caution for landscapes such as Australia’s tropical savanna, which supports a high diversity and abundance of small potential predators of artificial nests. There was no evidence of predation by birds, and the methodology proved inadequate for identifying predation by feral cats (Felis catus).
Acknowledgments
The research was carried out as part of a Ph.D. degree at the Australian National University and financial support was provided by the Tropical Savannas Cooperative Research Centre and the Parks and Wildlife Commission of the Northern Territory. Traditional Owners within Kakadu National Park and Parks Australia gave permission for research to be conducted within the park. The Northern Territory Museum allowed access to their mammal collection. We thank the Jim Jim District ranger staff for their cooperation and E. Astondae and M. A. Reid for assistance in the field. We are grateful to K. McGuinness and B. Brooke for statistical advice and D. C. Franklin, R. A. Noske, J. C. Z. Woinarski, P. A. S. Wurm and two anonymous referees for comments on drafts of this paper.
Batary, P. , and Baldi, A. (2004). Evidence of an edge effect on avian nest success. Conservation Biology 18, 389–400.
| Crossref | GoogleScholarGoogle Scholar |
Braithwaite, R. W. , and Werner, P. A. (1987). The biological value of Kakadu National Park. Search 16, 296–301.
Burkey, T. V. (1993). Edge effects in seed and egg predation at two neotropical rainforest sites. Biological Conservation 66, 139–143.
| Crossref | GoogleScholarGoogle Scholar |
Donovan, T. M. , Jones, P. W. , Annand, E. M. , and Thompson, F. R. (1997). Variation in local-scale edge effects: mechanisms and landscape context. Ecology 78, 2064–2075.
Gardner, J. L. (1998). Experimental evidence for edge-related predation in a fragmented agricultural landscape. Australian Journal of Ecology 23, 311–321.
Goosem, M. (2000). Effects of tropical rainforest roads on small mammals: edge changes in community composition. Wildlife Research 27, 151–163.
| Crossref | GoogleScholarGoogle Scholar |
Keyser, A. J. , Hill, G. E. , and Soehren, E. C. (1998). Effects of forest fragment size, nest density, and proximity to edge on risk of predation to ground-nesting passerine birds. Conservation Biology 12, 986–994.
| Crossref | GoogleScholarGoogle Scholar |
Leimgruber, P. , McShea, W. J. , and Rappole, J. H. (1994). Predation on artificial nests in large forest blocks. Journal of Wildlife Management 58, 254–260.
Picman, J. (1988). Experimental study of predation on eggs of ground-nesting brids: effects of habitat and nest distribution. Condor 90, 124–131.
Ricklefs, R. E. (1980). Geographical variations in clutch size among passerine birds: Ashmole’s hypothesis. Auk 97, 38–49.
Taylor, L. N. H. , and Ford, H. A. (1998). Predation of artificial nests in a fragmented landscape on the New England tablelands of New South Wales. Wildlife Research 25, 587–594.
| Crossref | GoogleScholarGoogle Scholar |
Yahner, R. H. , and Mahan, C. G. (1997). Effects of logging roads on depredation of artificial ground nests in a forested landscape. Wildlife Society Bulletin 25, 158–162.
Yahner, R. H. , and Wright, A. L. (1985). Depredation on artificial ground nests: effects of edge and plot age. Journal of Wildlife Management 49, 508–513.