Misdirected incubation in Common Kestrels Falco tinnunculus: a case of visual stimulus?

Abstract

The availability of suitable nesting sites may lead to interspecific competition and result in usurpation of these resources. Nest usurpation may result from a population increase of the usurping species and the limited availability of suitable nesting sites. With raptors, interspecific competition for nesting sites with other non-raptor bird species is a rarely documented phenomenon, particularly when it results in mixed interspecific clutches and misdirected reproductive behaviours. I observed a pair of Common Kestrels Falco tinnunculus, without its own clutch, incubating a clutch of two feral pigeon Columba livia eggs. The incubation occurred in the feral pigeons’ nest in southern xerophytic scrub on Tenerife Island during the 2020 breeding season. We checked the focal kestrel territory from 18 March to 20 May once a week. To our knowledge, this represents the first record of a Common Kestrel pair incubating eggs in the non-raptor bird species’ nest in the wild. We discuss some factors which could influence kestrels to display this behaviour.