BREEDING SUCCESS AND SURVIVAL IN THE COMMON SWIFT APUS-APUS - A LONG-TERM STUDY ON THE EFFECTS OF WEATHER

In an analysis of data collected between 1954 and 1993, the breeding s uccess of swifts Apus apus was found to have been positively related t o temperatures in June, especially in recent years. Adult survival unt il the next breeding season, by contrast, was found to have been more vulnerable to low temperatures in July, at the end of the breeding sea son. In addition to the effects of changes in June and July temperatur es, both breeding success and survival have shown further long-term tr ends, increasing and then decreasing through the study period. A simul ation integrating all these effects suggests that lifetime reproductiv e success (LRS) is influenced more by changes in lifespan than annual breeding success, and so fluctuations in July temperatures, but not Ju ne temperatures, would have important effects.