Breeding biology of the pallid swift (Apus pallidus) in north- western Italy

The birds begin to arrive in the 1st half of April; the last ones leave the region in November or in the 1st days of December. The 1st clutch is laid from mid-May to July, with most in the 1st half of June. In July some replacement clutches are laid, but true 2nd clutches started in September, when a highly variable percentage of birds (average 34%) nest for a 2nd time. The breeding success of the 1st brood is very similar to that of the common swift, autumn breeders suffer a high failure rate and their contribution to the annual reproduction rate is often very low. -from Authors