Land-use correlates of breeding performance and diet in Tree Sparrows Passer montanus

Capsule Chick diet varies seasonally and between wet and dry habitats, and there is little evidence for a link between habitat type and productivity. Aim To examine the influence of habitat composition and diversity on Tree Sparrow productivity and nestling diet in a wide variety of locations across the UK. Methods Productivity, chick diet and habitat data were collected from Tree Sparrow nestbox colonies by volunteer bird-ringers in 2002. Nestling diet was assessed by identification of invertebrate remains in faecal sacs. Results Clutch size was significantly higher for Tree Sparrows breeding in farmland than for those in wetland colonies. This did not translate into increased productivity. There was no other evidence of any effect of habitat or nestling diet composition on annual productivity. Diet composition varied seasonally, with habitat type and between individual sites. Conclusions Tree sparrows are capable of successful breeding in a range of habitats, where they utilize a wide range of invertebrate prey types. Lack of evidence for a relationship between habitat composition and productivity within this study may be the result of Tree Sparrows on farmland being restricted to areas providing adequate invertebrate food resources. To reduce the probability of Tree Sparrow populations on farmland being limited by chick food invertebrates, conservation measures aimed at population recovery should include the provision of habitats to support a range of high value invertebrate taxa throughout the protracted breeding season. Mechanisms to provide such habitats are already available within existing UK agri-environment schemes.