Spatial synchrony in red grouse population dynamics.

Abstract

Red grouse Lagopus lagopus scoticus populations exhibit unstable dynamics that are often characterised by regular periodic fluctuations in abundance. Time-series' of grouse harvesting records collected from 287 management units (moors) across Scotland, England and Wales were analysed to investigate the broad scale patterns of synchrony in these fluctuations. Estimation of the spatial autocorrelation of grouse population dynamics across moors indicates relatively high levels of synchrony between populations on adjacent moors, but that this synchrony declines sharply with increasing inter-moor distance. At distances of greater than 100 km, grouse population time-series exhibit only weakly positive cross-correlation coefficients. Twenty-eight geographical, environmental and other candidate variables were examined to construct a general linear model to explain variation in local synchrony. Grouse moor productivity (average size of shooting bag), distance from the Atlantic coast moving in a north-easterly direction, April and June temperatures, and June rainfall significantly increased the explanatory power of this model. An understanding of the processes underlying synchrony in red grouse population dynamics is a prerequisite to anticipating the effects of large-scale environmental change on regional patterns of grouse distribution and abundance.