The abundance of breeding Knot Calidris canutus islandica

Abstract

Six sites around Borup Fiord, west central Ellesmere Island, Canada, were surveyed for breeding Knot Calidris canutus islandica. Breeding density at the main study site was estimated using a calculation based on hatching success, brood counts and the probability of broods being resighted: estimates from other sites were based on this assessment. Density at the main study site was 4.6 pairs/km2, varying between 0.4 and 12.7 pairs/km2 in different areas. Density was negatively correlated with spring snow cover. At other sites density estimates ranged from nil to 5.7 pairs/km2. Brood counts and registrations of territorial activity accounted for only 33% and 67% of pairs, respectively. A literature review suggested that within the Knot's breeding range, densities appear to be highest in areas showing a warm regional climate, early snow-melt, and high vegetational diversity and density. The Knot's dependence on such areas may be related to its size and need for an early start to breeding. The total breeding population of C.c.islandica was estimated to be 61 000 pairs, or 304 000 individuals in autumn. Over-optimistic estimates of breeding numbers and productivity, however, may mean that about half of the Knots wintering in Europe may not be C.c.islandica. © 1998 British Trust for Ornithology.