THE ONSET OF INCUBATION IN BIRDS - CAN FEMALES CONTROL HATCHING PATTERNS

We investigated intraspecific variation in incubation behaviour of wil d Eurasian kestrels, Falco tinnunculus, in Finland and tested whether patterns of hatching asynchrony could be predicted from patterns of in cubation. The timing of the onset of incubation varied considerably fo r 17 female kestrels. Eggs generally hatched in the order they were la id, and both total hatching span of the clutch and the pattern of eggs hatching on certain days corresponded well with incubation behaviour. This result was consistent with the idea that females have much contr ol over hatching patterns. In the majority (65%) of cases, the proport ion of daily incubation increased monotonically with the laying sequen ce, a pattern described previously in other birds. Unusual patterns of incubation (35%) were most common in females with poor body condition during incubation and may be the result of energy constraints during laying. (C) 1998 The Association for the Study of Animal Behaviour.