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

We determined age-specific changes in survival probabilities and reproducti ve performance of female pied flycatchers, Ficedula hypoleuca Pallas, breed ing in the southern part of the species' breeding range in central Spain. O ur aim was to detect evidence of senescence in the course of a long-term st udy. 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 k nown-age birds were used to estimate age-dependent survival probabilities a ccording to capture-recapture models. I)ata on laying date, clutch size, nu mber 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 a fter that age the evidence For reproductive senescence was weak. Females in our study showed delayed senescence when compared to (i) another populatio n of the species breeding further north, (ii) the closely related collared flycatcher, and (iii) passerines in general. Middle-aged (3-4 years) female s in our population seemed to experience a relatively low extrinsic or age- independent mortality, which may favour a delayed ageing process. Low morta lity rates may be due to the short migration route and prolonged breeding s eason of southern pied flycatcher populations.