Effects of nest site location on energy expenditure and reproductive success in tits Shelley A. Hinsley1, Ross A. Hill1,*, Paul E. Bellamy1, Peter N. Ferns2, Nancy M. Harrison3, John R. Speakman4.
1Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire PE28 2LS, UK; e-mail: firstname.lastname@example.org
Great Tits Parus major and Blue Tits Cyanistes caeruleus are forest birds, but have adapted to live in many alternative habitats including secondary woodlands, woodland fragments, farmland, urban parks and gardens. Natural nest holes are often in short supply in such habitats and thus birds dependent on nest boxes may be constrained by habitat quality “imposed” on them by the arbitrary location of a box. We examine the effects of habitat structure (mean tree height and the presence of gaps) and tree species composition (presence of oak) around the nest site on reproductive success and the costs of rearing young in tits breeding in boxes in deciduous woodland and urban parkland. Daily energy expenditure (DEE) of adults feeding 11 day old young was measured using doubly labelled water. Habitat structure and composition were derived from airborne remote sensed Light Detection and Ranging (LiDAR) and Airborne Thematic Mapper (ATM) data. DEE was greater in parkland birds and increased with decreasing mean tree height and increasing gap around the box, with a threshold effect at about 35% gap. In woodland, DEE increased as oak around the box decreased. Reproductive success in parkland was poor and more variable compared to woodland.