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Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins

Ekanayake, Kasun B., Sutherland, Duncan R., Dann, Peter and Weston, Michael A. 2015, Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins, Wildlife research, vol. 42, no. 6, pp. 509-517, doi: 10.1071/WR15108.

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Title Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins
Author(s) Ekanayake, Kasun B.
Sutherland, Duncan R.
Dann, Peter
Weston, Michael A.ORCID iD for Weston, Michael A. orcid.org/0000-0002-8717-0410
Journal name Wildlife research
Volume number 42
Issue number 6
Start page 509
End page 517
Total pages 9
Publisher CSIRO
Place of publication Melbourne, Vic.
Publication date 2015
ISSN 1035-3712
Summary Context Egg depredation is a major cause of reproductive failure among birds and can drive population declines. In this study we investigate predatory behaviour of a corvid (little raven; Corvus mellori) that has only recently emerged, leading to widespread and intense depredation of eggs of a burrow-nesting seabird (little penguin; Eudyptula minor). Aims The main objective of this study was to measure the rate of penguin egg depredation by ravens to determine potential threat severity. We also examined whether penguin burrow characteristics were associated with the risk of egg depredation. Ravens generally employ two modes of predatory behaviour when attacking penguin nests; thus we examined whether burrow characteristics were associated with these modes of attack. Methods Remote-sensing cameras were deployed on penguin burrows to determine egg predation rates. Burrow measurements, including burrow entrance and tunnel characteristics, were measured at the time of camera deployment. Key results Overall, clutches in 61% of monitored burrows (n≤203) were depredated by ravens, the only predator detected by camera traps. Analysis of burrow characteristics revealed two distinct types of burrows, only one of which was associated with egg depredation by ravens. Clutches depredated by ravens had burrows with wider and higher entrances, thinner soil or vegetation layer above the egg chamber, shorter and curved tunnels and greater areas of bare ground and whitewash near entrances. In addition, 86% were covered by bower spinach (Tetragonia implexicoma), through which ravens could excavate. Ravens used two modes to access the eggs: they attacked through the entrance (25% of burrow attacks, n≤124); or dug a hole through the burrow roof (75% of attacks, n≤124). Burrows that were subject to attack through the entrance had significantly shorter tunnels than burrows accessed through the roof. Conclusions The high rates of clutch loss recorded here highlight the need for population viability analysis of penguins to assess the effect of egg predation on population growth rates. Implications The subterranean foraging niche of a corvid described here may have implications for burrow-nesting species worldwide because many corvid populations are increasing, and they exhibit great capacity to adopt new foraging strategies to exploit novel prey. Journal compilation
Language eng
DOI 10.1071/WR15108
Field of Research 050202 Conservation and Biodiversity
05 Environmental Sciences
06 Biological Sciences
Socio Economic Objective 960802 Coastal and Estuarine Flora, Fauna and Biodiversity
HERDC Research category C1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2015, CSIRO
Persistent URL http://hdl.handle.net/10536/DRO/DU:30080316

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