Predators and nest success of Sky Larks Alauda arvensis in large arable fields in the Czech Republic.

摘要

Capsule: Nest failure owing to a range of predators was high, but the level and specificity of nest depredation cannot be generalised. Aims: To determine fates and predators of Sky Lark nests in conventionally managed arable fields in the Czech Republic. Methods: Sky Lark nests in large fields (mainly Maize, Sugar Beet and Opium Poppy) were monitored by means of continuous video surveillance. Results: Primary nest fates of 42 active nests were fledging (13), depredation (22), desertion (5), nestling death (1), and flooding (1). The overall nest success (Mayfield estimate) was 17% (all mortality factors considered) or 27% (only depredation). Depredation events were caused by Marsh Harrier Circus aeruginosus (11), Hooded Crow Corvus cornix (4), Stone Marten Martes foina (3), Montagu's Harrier Circus pygargus (2), Red Fox Vulpes vulpes (2), Hedgehog Erinaceus sp. (2) and Eurasian Jackdaw Corvus monedula (1). Successful nests were only slightly more away from field edge than depredated nests; nests taken by birds tended to be closer to field edge than those depredated by mammals. The possible reasons for the absence of a clear edge effect include comparatively large field parcels (about 50 ha) and location of nests far from field edge (median=195 m). Conclusion: Nest survival and composition of nest predators are site-specific and contingent upon the study method and may not be simply generalised.