PHENOLOGY, BREEDING DENSITY AND POPULATIO N ECOLOGY OF THE GARDEN WARBLER SYLVIA BORIN IN A SUB-ALPINE HABITAT OF THE CENTRAL SWISS ALPS

WIDMER M

M. Widmer, PHENOLOGY, BREEDING DENSITY AND POPULATIO N ECOLOGY OF THE GARDEN WARBLER SYLVIA BORIN IN A SUB-ALPINE HABITAT OF THE CENTRAL SWISS ALPS, Journal fur Ornithologie, 137(4), 1996, pp. 479-501

54

TEDESCO

Article

Ornithology

Journal fur Ornithologie → ACNP

0021-8375

137

4

1996

479 - 501

ISI

0021-8375(1996)137:4<479:PBDAPN>2.0.ZU;2-M

A population of Garden Warbler was studied in a natural habitat in the Urseren valley (1500 m a. s. l.) for 7 years. The aim of this study w as to describe the migration phenology and to evaluate if a self-susta inable population of this long distance migrant can exist under unfavo urable climatic conditions. In spring, the Garden Warblers arrive abou t 3 weeks later, but in late summer they leave their territories at th e same time as their conspecifics in the lowlands. Possible consequenc es of the restricted breeding period for juvenile development and migr ation schedule are discussed. In the study area, a very high breeding density (25 territories/10 ha) was recorded. The birds show a remarkab le breeding and natal site fidelity (48 % of adults and 6 % of nestlin gs returned the following year). The overall breeding success was 48 % . The main causes of failure were predation and bad weather events. Th e latter were responsible for the annual fluctuations of breeding succ ess. In conclusion, this study confirms that self-sustainable populati ons of this long-distance migratory species exist in mountain habitats .