Seasonal variation in the diet of stoats in a breeding colony of Hutton’s shearwaters

Abstract

The diet of stoats (Mustela erminea) was studied in the Kowhai valley colony of Hutton’s shearwaters (Puffinus huttoni). Remains of Hutton’s shearwaters were found in 785 of 788 scats examined. Scats contained remains of eggs, chicks, near fledging age chicks and adult shearwaters, as well as the remains of skinks (Oligosoma sp.) and weta (Deinacrida sp.). There was seasonal variation in the frequency of occurrence of all major prey items. Stoats switched from taking predominantly adults during the pre‐egg and incubation periods, to taking almost exclusively chicks during the chick‐rearing period. The impact of stoats on Hutton’s shearwaters may as a consequence of this prey switch be reduced, because the population is likely to be more affected by the loss of adults rather than chicks. Stoats continued to feed upon shearwaters, even after all birds had left the colony. Remains of mice (Mus musculus) and hares (Lepus europaeus) were infrequently found in scats, although the occurrence of these along with the occurrence of skinks and weta increased after all live shearwaters had departed. The results suggest that stoat numbers may be limited by the availability of over‐winter prey within the colony. © 2000 Taylor and Francis Group, LLC.