Can burrow-nesting seabirds be identified from their burrow dimensions?

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Wildlife Society Bulletin


To reduce disturbance, the Alaska Maritime National Wildlife Refuge indirectly calculates the densities of burrow-nesting seabirds by counting numbers of small-, medium-, and large-width burrows and assuming that birds occupy burrows equivalent to their body size. Burrow-width criteria that differentiate species are based on data collected in British Columbia, but may not be appropriate for other sites. Our objectives were to evaluate and improve this method at an annual monitoring site on Buldir Island, Alaska. During 1995 and 1996, we measured width and height of 391 burrows and subsequently verified the species occupying each burrow. We found that the current model incorrectly predicted the species in 38% of the burrows. To improve accuracy of the method, we revised the burrow-size criteria based on mean burrow width and height for each species. The revised size classes were correlated significantly with the expected species and predict- ed the correct species in 80% of the burrows. We then used the revised size criteria to design a measuring device to distinguish between species at the burrow entrance. The improvement in species prediction from the revised size criteria suggests that the meas- uring device can be used to monitor densities of burrow-nesting seabirds accurately, quickly, and with negligible disturbance at Buldir Island, Alaska.







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