Patterns of breeding fidelity in the Red-backed Shrike (Lanius collurio)

Abstract

Breeding fidelity was studied in Red-backed Shrike, Lanius collurio, in the Czech Republic from 1990 to 1999. The males tend to return more frequently than females, both to the whole research area and to the particular territory. The return rates for both sexes fluctuated from year to year . Male fluctuation was correlated with population density, whereas female fluctuation reflected the previous year's population nesting success ofthe first breedings. Older birds exhibited non-significantly higher philopatry . The territorial fidelity of males was found to be affected by breeding success and territory attractiveness . Breeding success was important also for female return rate . Most reproductive parameters (clutch size, eggs hatched, young fledged, asynchronous growth of young) were not correlated with the rate of philopatry of either of the sexes. Future philopatric females started their breeding earlier than others . Mate fidelity was recorded twice, apparently as a random result . Maximum age was 6 years (male) . No more than 3-4% of young returned to breed in the natal area . Low return rates are believed to be the result of migration of both young and adult birds out of the research area .