Seasonal pattern in hawk predation on Common Bullfinches Pyrrhula pyrrhula: evidence of an interaction with habitat affecting food availability: Capsule Where predators occur, Bullfinch populations are probably limited as much by landscape structure as by

Publication Type:Journal Article
Year of Publication:2007
Authors:Marquiss, M
Journal:Bird Study
Volume:54
Issue:1
Date Published:2007
ISBN Number:0006-3657
Keywords:Accipiter, Accipiter nisus, Accipitridae, Fringillidae, Nisus, Passer, Passer montanus, Passeridae, Pyrrhula, Pyrrhula pyrrhula
Abstract: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.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.
URL:http://www.tandfonline.com/doi/abs/10.1080/00063650709461451
Short Title:Bird Study
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith