Delayed senescence in a southern population of the pied flycatcher (Ficedula hypoleuca)

Abstract

We determined age-specific changes in survival probabilities and reproductive performance of female pied flycatchers, Ficedula hypoleuca Pallas, breeding in the southern part of the species’ breeding range in central Spain. Our aim was to detect evidence of senescence in the course of a long-term study. A sample of known-age individuals, as well as a larger set of birds of minimum age, was used for analyzing reproductive performance, while only known-age birds were used to estimate age-dependent survival probabilities according to capture-recapture models. Data on laying date, clutch size, number of fledglings, and number of recruits produced were analyzed. Survival probabilities increased from 1-2 years to 3-4 years of age. No decline in reproductive performance was detected before the age of 5 years, and even after that age the evidence for reproductive senescence was weak. Females in our study showed delayed senescence when compared to (i) another population of the species breeding further north, (ii) the closely related collared flycatcher, and (iii) passerines in general. Middle-aged (3-4 years) females in our population seemed to experience a relatively low extrinsic or age-independent mortality, which may favour a delayed ageing process. Low mortality rates may be due to the short migration route and prolonged breeding season of southern pied flycatcher populations.