The importance of altitude and aspect for breeding Whinchats Saxicola rubetra in the uplands: limitations of the uplands as a refuge for a declining, formerly widespread species?

摘要

Capsule: The likelihood of an area being occupied by breeding Whinchats was inversely related to altitude, and areas with south- and east-facing aspects were favoured over those with north- and west-facing aspects. Aims: To identify habitat features and physical attributes of Whinchat territories in upland areas of the UK. Methods: Comparison of habitat features and physical attributes measured at random points within territories and >100 m from a territory in an area with a relatively high breeding density were used to identify factors associated with Whinchat occurrence in upland Scotland. Further data were extracted from recent independent surveys conducted elsewhere in upland Britain. Results: Within a favoured habitat (young sparse shrubs and developing ground vegetation) in the main study site, the probability of an area with south- and east-facing aspects being occupied by breeding Whinchats exceeded 80% below 300 m asl and declined linearly to less than 20% above 500 m. For areas with north- and west-facing aspects, the probability of occupancy at 300 m was 40% and close to zero at 500 m. Territory size increased with altitude. Data from elsewhere in upland Britain supported an association of altitude and aspect with Whinchat territories but suggested that such environmental limitations differed between regions. Conclusion: Within marginal uplands, Whinchats could be constrained at their lower altitudinal limit by intensive agricultural land-use and at their upper altitudinal limit by environmental restrictions on their breeding biology. Such limitations need to be considered if such areas are to continue to support viable populations of a declining and formerly widespread species.Digital Object Identifier http://dx.doi.org/10.1080/00063657.2011.623767