Supernormal clutches of American Kestrels (Falco sparverius) in peninsular Florida

Abstract

The clutch size of the American Kestrel (Falco sparverius) has been well studied across a range of latitudes and habitats and typically is 4 or 5 eggs. Neither polygyny nor brood parasitism has been reported for the species. I report here 3 instances of supernormal clutches, of 8 or 9 eggs, documented in kestrel nest boxes in north-central Florida and discuss 4 possible explanations for these observations. In 2 nests only 1 egg hatched, and in 1 nest none of the eggs hatched. Although I was unable to make a conclusive finding about the cause for supernormal clutches, it is likely that they were laid by more than 1 female, either cooperatively or non-cooperatively.