Biometrics and survival rates of Pallid SwiftsApus pallidusin Portugal

A colony of Pallid Swifts Apus pallidus in the Serra da Arrábida (Southern Portugal) was visited regularly during seven consecutive breeding seasons (from 1990 to 1996) in order to study the birds’ biometrics and survival rates through capture and recapture. Wing‐length and weight measurements were taken; wing‐length values corroborate the hypothesis of a west to east clinal variation in wing size within the distribution range of the sub‐species A. p. brehmorum. Annual survival rates varied between 0.75 and 0.86 during the breeding seasons from 1990 to 1995, and a significant correlation was found between survival rates and the rainfall indices from the Sahel region of Africa, where the species winters.