1982 年 14 巻 2-3 号 p. 157-165
Suspended moult is a special adaptive moult strategy which is widespread in long-distance migrants. The replacement of remiges and rectrices in this type of moult starts before migration but then is interrupted during migration. So far, it has virtually not been investigated experimentally. We carried out an investigation on the Orphean Warbler, Sylvia hortensis, an European trans-Saharan migrant known commonly to suspend its moult. We studied 15 trapped adults and 8 handraised young individuals, which were kept in light conditions simulating those to which freeliving conspecifics are normally exposed in the course of a year. In the first experimental year, the adults, caught during breeding, all suspended their moult and retained some old primaries, secondaries, and tertials. In the second experimental year, when the same birds were prevented from breeding, they moulted weeks earlier, and, as a result, completed their moult before the migratory period. Similarly, the handraised birds showed a complete moult in their second year. Thus, the suspended moult of the Orphean Warbler is not based on strictly endogenously controlled moult programs with preprogrammed moult pauses. Moult in this species can be adapted on a facultative basis to various conditions experienced. The course of the moult and its suspension appear to be linked to the preceeding individual breeding season, and some conceivable control mechanisms are discussed in detail.