An experimental test of offspring recognition in the colonial Lesser Kestrel Falco naumanni

Offspring recognition is necessary to avoid the costs of alloparental care, which may include decreased adult survival and reproductive success (Bustamante & Hiraldo 1990, Saino et al. 1994, Brown 1998). However, recognition mechanisms are not cost-free, as any identification error could result in attacks on, or abandonment of, a true descendant (Brown 1998). Consequently, offspring recognition is expected only when the risk of intrusion of alien young is high and ⁄ or caring for them costly (Beecher 1991). We performed a manipulative experiment in the Lesser Kestrel Falco naumanni to test the existence of offspring recognition, but found little evidence that they could consistently identify their own offspring. Amongst altricial species, offspring recognition has evolved in colonial species, especially seabirds, where the probability of intrusions by alien nestlings is high (Lefevre et al. 1998, Insley et al. 2003, Searby & Jouventin 2005). Amongst raptors, most species are solitary breeders, but there are species such as the Lesser Kestrel which form breeding colonies. These colonies were originally placed on cliffs, but nowadays most European Lesser Kestrels breed in buildings (González & Merino 1990). In this species, adoptions have been reported (Donázar et al. 1991, Tella et al. 1997), but no direct test of parental recognition capacity has yet been carried out. We performed a manipulative experiment with the Lesser Kestrel to test directly the capacity of parents to recognize their offspring after removing any effect of nest-site recognition. In addition, we analysed whether offspring recognition differed between males and females.