SEASONAL BODY MASS AND HABITAT SELECTION OF SOME MIGRATORY PASSERINES OCCURRING IN ISRAEL

ABSTRACT

Migratory passerines were mist-netted during the spring and autumn migrations at two localities in Israel: Ein Fashkha, a desert oasis near the Dead Sea, and Elon, a maquis vegetation area in the western Galilee. In both localities, mean body mass of the blackcap (Sylvia atricapilla) was significantly heavier in autumn, and heavier in the Galilee than in the oasis. More blackcaps were netted in spring at both sites. The robin (Erithacus rubecula) had heavier body mass in spring, and its capture rate was higher in autumn. In autumn, the blackcap passes through Israel loaded with fat on its way south to its winter quarters in East Africa. In spring, it arrives in relatively poor body condition after crossing the Sahara. A higher capture rate during springtime could be explained by the poor condition of the birds. The robin winters in Israel, and birds captured in autumn have just completed their migration, and carry little fat reserves, while those caught in spring are loaded with fat for their northward migration. Mean wing length of the reed warbler (Acrocephalus scirpaceus) was significantly longer in spring than in autumn. This is consistent with the species completing its moult in winter quarters and arriving in Israel in spring with relatively fresh feathers. Species composition at each locality indicates that most migrant species examined prefer habitats similar to those used during the breeding season.