Fettupplagring och inledande höstflyttningshastighet hos juvenila blåhakar Luscinia s. svecica i Lappland

Abstract

The period between independence and the early phase of autumn migration is a difficult period for juvenile birds and a relatively poorly known part of the annual cycle. We present data on post-juvenile moult, fuel deposition and speed of early autumn migration of "red-spotted" Bluethroats Luscinia s. svecica, studied during 14 years (1984—1997) in Ammarnäs, Swedish Lapland. The juvenile Bluethroats leave their natal site from early August onwards, while still being in active post-juvenile moult. They do not put on any noticeable fuel stores, probably because foraging conditions are generally poor. This is reflected in a very slow initial speed of migration (11–21 km/d) between the natal area and stopover sites in eastern Sweden.