Relationships between bird abundance and the composition and structure of moorland vegetation

Abstract

Capsule Variations in the composition, structure and heterogeneity of moorland vegetation are shown to affect the abundance of eight of nine moorland bird species, with implications for grazing management. Aims To determine how variation in vegetation characteristics affects breeding bird abundance on moorlands. Methods Bird and habitat data from 85 2-km2 plots in south Scotland and northern England were analysed using multivariate analysis to disentangle vegetation effects from confounding site and management effects. Results Of nine species studied in detail, Red Grouse Lagopus lagopus scoticus and Stonechat Saxicola torquata were associated with Heather Calluna vulgaris, although both favoured some heterogeneity in cover. Meadow Pipit Anthus pratensis demonstrated a curvilinear relationship with Heather cover, whilst both Curlew Numenius arquata and Snipe Gallinago gallinago were most abundant where vegetation structure was relatively heterogeneous. Skylark Alauda arvensis and Golden Plover Pluvialis apricaria were positively associated with short vegetation, in particular short grass and short dwarf shrub cover, respectively. Whinchat Saxicola rubetra was associated with dense vegetation, particularly Bracken Pteridium aquilinum, but no strong vegetation effects were detected for Wheatear Oenanthe oenanthe. Six of the nine species showed positive associations with vegetation typical of wet conditions. Conclusions Moorland birds vary in their preferences for particular compositional and structural vegetation features, and management promoting heterogeneity and wetland vegetation is likely to support a diverse bird community and benefit certain key species. Losses of Heather cover in recent decades, primarily from increased grazing levels, appear likely to have reduced habitat availability for only two of the nine species studied.