SEASONAL BODY-MASS AND HABITAT SELECTION OF SOME MIGRATORY PASSERINESOCCURRING IN ISRAEL

Migratory passerines were mist-netted during the spring and autumn mig rations at two localities in Israel: fin Fashkha, a desert oasis near the Dead Sea, and Elon, a maquis vegetation area in the western Galile e. In both localities, mean body mass of the blackcap (Sylvia atricapi lla) was significantly heavier in autumn, and heavier in the Galilee t han in the oasis. More blackcaps were netted in spring at both sites. The robin (Erithacus rubecula) had heavier body mass in spring, and it s capture rate was higher in autumn. In autumn, the blackcap passes th rough Israel loaded with fat on its way south to its winter quarters i n East Africa. In spring, it arrives in relatively poor body condition after crossing the Sahara. A higher capture rate during springtime co uld be explained by the poor condition of the birds. The robin winters in Israel, and birds captured in autumn have just completed their mig ration, and carry little fat reserves, while those caught in spring ar e loaded with fat for their northward migration. Mean wing length of t he 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 rel atively fresh feathers. Species composition at each locality indicates that most migrant species examined prefer habitats similar to those u sed during the breeding season.