Modelling habitat preference of corvids (family: corvidae) in Scotland : a landscape perspective
Understanding landscape function is one of the core research topics in landscape ecology. Establishing the relative importance of landscape factors and other environmental factors is a key issue. Six members of crow family (Corvidae: jay, Garrulus glandarius; magpie, Pica pica; jackdaw Corvus monedula; rook, Corvus frugilegus; Eurasian crow, Corvus corone; raven, Corvus corax) in Scotland are used to examine these factors. The approach explores the value of the concept of multi-dimensional space in studying habitat. The proportions of different land cover types, the woodland landscape and entire landscape patterns are quantified and tested against the distribution and abundance of corvids. In a specific case study, other environmental factors (elevation, rainfall and temperature) are introduced to help identify the main factors determining the geographic location of the hybrid zone of carrion and hooded crows (Corvus corone corone and C. c. cornix). Finally, a hierarchical model based on path analysis is used to rank environmental variables in terms of their relative influence on species abundance, richness and diversity. The results show that while the diversity of corvid species is strongly correlated with landscape patchiness, the associations between corvid abundance and environmental factors are species specific. The climatic factors are shown to be significant factors in explaining the westward shift of the hybrid zone of carrion and hooded crows over the last 70 years. The habitat requirements of corvids revealed in this study demonstrate a marked contrast with those revealed by studies in continental Europe. These differences are interpreted in terms of the mechanism of habitat shifting.