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Burrow entrance attrition rate in wedge-tailed shearwater Puffinus pacificus colonies on Rottnest Island, Western Australia

Bancroft, W.J., Roberts, J.D. and Garkaklis, M.J. (2005) Burrow entrance attrition rate in wedge-tailed shearwater Puffinus pacificus colonies on Rottnest Island, Western Australia. Marine Ornithology, 33 (1). pp. 23-26.

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Shearwaters (Puffinus spp.) appear to select burrow-nest sites to minimise the risk of burrow collapse and are known to clear and re-excavate damaged burrows, yet empirical evidence on the incidence of burrow collapse is lacking. We provide preliminary data on rates of burrow entrance collapse in a colony of Wedge-tailed Shearwaters (P. pacificus) on Rottnest Island, Western Australia. Entrances to 67.8% of burrows that were active during the laying phase of the 2002/03 breeding season had collapsed by the beginning of the next season. The attrition rate was linear over time, and collapsed portions had a mean length of 17.9 ± 2.7 cm (standard error). Burrow entrances overlain with shallow-rooted, annual plants (89.7% collapse rate) were more than twice as likely to collapse as those located beneath deeper-rooting, perennial shrubs (40.9% collapse rate). Three quarters of collapsed entrances were re-excavated the following season, and at least 11.5 t ha -1 yr -1 (8.5 m 3 ha -1 yr -1) of soil was displaced through this process. Of marker posts that were placed at the entrances of burrows in 1992 (n = 264), 22% were found in 2003. Of the posts that were found, 19% remained associated with a burrow entrance. We consider that most entrance collapses in this study reflect abandonment of burrows by the birds. Our data predict that, if a current increase in shallow-rooted vegetation in colony areas continues, the rate of entrance collapse and colony erosion will increase. Although we did not attempt to quantify the effect that burrow entrance collapse has on the reproductive biology of the shearwaters, we hope that our work will catalyse future investigation in this field.

Item Type: Journal Article
Murdoch Affiliation(s): School of Biological Sciences and Biotechnology
Publisher: Marine Ornithology
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