Present address: Centre for Environmental Sciences, School of Civil Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
Gap-crossing decisions of woodland songbirds in Scotland: an experimental approach
Article first published online: 8 AUG 2005
Journal of Applied Ecology
Volume 42, Issue 4, pages 678–687, August 2005
How to Cite
CREEGAN, H. P. and OSBORNE, P. E. (2005), Gap-crossing decisions of woodland songbirds in Scotland: an experimental approach. Journal of Applied Ecology, 42: 678–687. doi: 10.1111/j.1365-2664.2005.01057.x
- Issue published online: 8 AUG 2005
- Article first published online: 8 AUG 2005
- Received 6 October 2004; final copy received 23 March 2005 Editor: Rob Freckleton
- forest habitat networks;
- habitat fragmentation;
- mobbing behaviour
- 1Recent declines in woodland birds in Britain have been linked to increasing habitat fragmentation. To understand the effects of fragmentation, data on avian dispersal across woodland gaps are essential but often lacking.
- 2We used song thrush Turdus philomelos mobbing calls to attract songbirds across gaps ranging from 5 to 120 m in width and along comparable woodland edges. Responses were modelled against distance using generalized linear models. Such models have clear applied value for connecting fragmented landscapes.
- 3We also calculated response indices and compared these with bird morphology. The gap-crossing results were applied to a real landscape in central Scotland and landscape metrics were calculated to judge how perception of habitat connectivity varies interspecifically.
- 4The chaffinch Fringilla coelebs and the robin Erithacus rubecula both responded more readily across gaps than through woodland. There was no difference between gap and edge response for the coal tit Parus ater, while the goldcrest Regulus regulus responded more readily along edges than across gaps. Maximum gap-crossing distances ranged from 46 m (goldcrest) to 150 m (chaffinch).
- 5There was a positive linear trend between mass of bird and the difference in the maximum response for gap and control experiments. Likewise there was a positive curvilinear relationship between wing area and the difference in probability of response between gap and control experiments at 50 m. These results may be interpreted in terms of manoeuvrability and ability to escape avian predation.
- 6For the central Scotland landscape, the perceived number of patches in the landscape decreased exponentially with increasing gap-crossing distance, while the median patch size and mean patch fractal dimension increased linearly with gap-crossing distance.
- 7Synthesis and applications. Our results show that an experimental approach using playback can be used to obtain data on avian gap crossing and the results applied to real landscapes to visualize interspecific differences in habitat perception. This has practical management applications, especially for designing forest habitat networks to maximize avian biodiversity, and potentially could help reverse the recent declines in woodland birds.