Nesting success, density, philopatry, and nest-site selection of the Whimbrel (Numenius phaeopus) in different habitats

A population of Whimbrels (Numeniusphaeopus) that nested in three distinct habitats near Churchill, Manitoba, was studied from 1973 to 1976. Nest success in the hummock–bog habitat was 86% and was significantly higher than the 54% success in each of the sedge–meadow and heath–tundra habitats. The hummock–bog habitat differed from the other two in several other respects. In the hummock–bog habitat, density of nesting pairs was highest and averaged 0.11 pairs/ha. Distribution of nests tended toward uniform. Density in sedge–meadow and heath–tundra habitats averaged 0.04 and 0.05 pairs/ha, respectively. Philopatry of banded adults to the hummock–bog habitat was considerably higher than to the other two, indicating more stability there. Several attributes of nest placement were important, and the hummock–bog habitat, structurally the most complex, offered more potentially favorable sites. The higher nesting success in the hummock–bog habitat was attributed primarily to the more complex structure of this habitat (crypticity is enhanced) and the higher nesting density (predation is reduced through joint defense).