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Seasonal pattern in hawk predation on Common Bullfinches Pyrrhula pyrrhula: evidence of an interaction with habitat affecting food availability

Marquiss, Mick. 2007 Seasonal pattern in hawk predation on Common Bullfinches Pyrrhula pyrrhula: evidence of an interaction with habitat affecting food availability. Bird Study, 54. 1-11.

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Abstract/Summary

Aims To explore the interaction between food, cover and predation by comparing the seasonal patterns of the foraging behaviour of Common Bullfinches, with their frequency in the diet of Eurasian Sparrowhawks Accipiter nisus. Methods Foraging Bullfinches were observed in northeast Scotland from 1997 to 2004, documenting seasonal patterns in foods, proximity to cover, and relative abundance in three habitats. Seasonal changes in predation were assessed from the plucked remains of passerines killed by Sparrowhawks. Results The seasonal sequence and diversity of foods used by Bullfinches are described. Only rarely did they forage far from cover, mainly in December to February. Their relative abundance in three habitats suggested that they concentrated increasingly in uplands during winter, where they fed on heather seed at gradually higher elevations through to February. Within samples of plucked passerines, full-grown Bullfinches occurred predominantly in winter, newly fledged juveniles only in late summer and autumn. Bullfinches aggregated during autumn and winter, in particularly large groups when foraging on heather far from tree cover. Conclusions Seasonal patterns of predation and foraging behaviour fit the idea that Bullfinches are vulnerable to predation when a limited choice of food obliges them to forage far from cover. In the presence of Sparrowhawks, the food supply of Bullfinches is determined not by food abundance alone, but by its abundance in close proximity to cover. Key foods are those used when seed availability is at a seasonal low, prior to the switch to buds. Bullfinch population size is probably determined by food supply within habitat configurations at two spatial scales.

Item Type: Publication - Article
Programmes: CEH Programmes pre-2009 publications > Biodiversity
CEH Sections: Watt
ISSN: 0006-3657
Format Availability: Electronic, Print
Additional Keywords: Pyrrhula, Bullfinch, Common Bullfinch, predation, hawks, Sparrowhawk, Eurasian Sparrowhawk, Accipiter, habitat mosaic, Calluna vulgaris, heather
NORA Subject Terms: Zoology
Ecology and Environment
Date made live: 22 Aug 2007 15:42
URI: http://nora.nerc.ac.uk/id/eprint/797

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