A study of the return rate and dispersal of Sand MartinsRiparia ripariaat a single colony

Abstract

Sand Martins were trapped at an Oxfordshire colony during 1979–83. The return rate of adult males in following years was higher than for adult females, and adult females dispersed more than adult males in subsequent breeding seasons. The return rate of adults in the first year after capture appeared lower than in subsequent years but this was an artefact due to the catching efficiency being less than 100%. Birds ringed as juveniles had a much lower return rate than adults but many of them were probably passage birds. Juvenile males had a much higher return rate than juvenile females, with the females much more dispersive. The return rate of known second-year birds, which were heavily male biased, was higher than that of all adults, but not significantly different from that of adult males. Lower adult return rates and decreased recruitment from juveniles both contributed to the decline of the colony, both probably being the result of decreased winter survival.