Regional, seasonal and annual variations in the structure of Purple Sandpiper Calidris maritime populations in Britain

Abstract

Samples of Purple Sandpipers were captured around the coasts of Britain. Analysis of their bill‐length distributions enabled the sex ratios and percentages of ‘long‐billed’ and ‘short‐billed’ birds at each locality to be estimated. The sex ratio for the ‘long‐billed’ population was estimated to be one female to 2–11 males, and one female to 1 ‐34 males for the ‘short‐billed’ population. During winter, proportionately more ‘long‐billed’ birds occurred in northern and western Scotland, Wales and southern England, whilst ‘short‐billed’ birds predominated from Kincardine to Yorkshire. The total sizes of the ‘long‐’ and ‘short‐billed7’ populations were c. 15 000 and 4000, respectively. ‘Short‐billed’ birds started arriving from Norway in early July. ‘Long‐billed’ birds did not arrive until late October. Their origins are as yet unknown. No annual variations in the population structure were detected.