Long term changes in weather and in the breeding schedule of Common Swifts Apus apus

THOMPSON D.L. and THE LATE HENRY DOUGLAS HOME.

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Abstract:

At a small colony in Southern Scotland, long term changes in weather, have been associated with correponding changes in the date at which the chicks of Common swifts Apus apus, have. reached the later stages of development. The dates at which the young have reached a suitable stage for n~gmg, have been significantly influenced by rainfall and temperatures m May and June. Ali of these vanables have shown regular changes through time. There is also some evidence that July tempe~atures may also have changed through time and had additional effects. While the strong effects of weather m the early part of the season are consistent with there being effects of laying date and incubation period on changes in the breeding schedule, the changes in June and July weather during the later stages of breeding, may have had effects on chick growth rates which are known to be highly flexible in this species.