The use of GIS in estimating spatial variation in habitat quality: a case study of lay-date in the Great Tit Parus major

Finding the most biologically meaningful scale at which to describe environmental variation is a persistent problem in ecology. Most studies of forest passerines are conducted at the scale of the habitat or woodland and do not account for environmental variation between individual breeding sites. Here we employ two GIS models, and four spatial scales, to describe environmental variation among 4683 Great Tit Parus major breeding sites occupied over a 32-year period in Wytham Wood, Oxford, UK, and use these data to help explain variation in an environmentally sensitive trait, first egg date. Model 1 used Thiessen polygons to generate individual spatial scales for each breeding pair, while Model 2 used a range of predetermined radial scales around each breeding site. Environmental variables included local altitude and aspect estimated from a Digital Terrain Model, and the number of Oak Quercus robur trees around each nest-site, used here as a surrogate for local food (caterpillar) availability.

TEDDY A. WILKIN, CHRISTOPHER M. PERRINS & BEN C. SHELDON, Ibis 149 (s2), 110-118.