Use of environmental stratification to derive non-breeding population estimates of dispersed waterbirds in Great Britain

Population estimates provide a baseline to inform conservation and management decisions. In this paper, we present a novel method to derive non-breeding population estimates of waterbirds in Great Britain. We combined Wetland Bird Survey (WeBS) data with a detailed environmental stratification to calculate population estimates for widely dispersed waterbird species, populations of which tend to be relatively poorly monitored by WeBS and other established schemes. These stratification-based estimates were then compared with published estimates, most of which were derived using extrapolations based on WeBS information and a small number of intensive surveys. We discuss the limitations and merits of the stratification method, and conclude by suggesting the species for which future use of the approach would be most appropriate for derivation of population estimates. We also outline potential ways to improve the baseline information on abundance of widely dispersed non-breeding waterbirds in Great Britain.