Weights and fat accumulation of blackcaps sylvia atricapilla during migration through southern spain

Abstract

The weights and fat of Blackcaps during autumnal and spring passages through Southern Spain have been studied. The birds passing during autumn have mean weight of 19.2 g, superior to the birds which winter in these areas (Herrera and Jordano 1981); 82.5% winter in the Mediterranean Basin (probably in Northern Africa) and 17.5% are long‐distance migrants. The latter birds have a weight greater than 21 g, and they can be considered as long‐distance migrants (Langslow 1976). The birds passing during the spring, with a mean weight of 22.3 g, are distributed into two groups with different weights and with different fat accumulations which must represent different migratory strategies related to their nesting areas. This supposition is supported by various authors that relate different weight and fat deposition in populations of one species with distinct areas for breeding or wintering (Berthold 1975, Ash 1969). © 1985 Taylor & Francis Group, LLC.