First record of cooperative nesting in the Eagle Owl Bubo bubo

Monogamy appears to be the most commonmating system amongst raptors and owls. However,alternative breeding strategies have beendescribed (i.e. polygyny, polyandry and cooperativebreeding; Newton, 1979; Mikkola,1983; Del Hoyo et al., 1999; Hatchwell &Komdeur, 2000). Recent studies have shownthat co-operative breeding is much more widespreadthan had previously been thought; indeed,it has been observed in at least 3% of birdspecies, including as many as 42 birds ofprey (Kimball et al., 2003) and 10 owls (Markset al., 1999).

Jose Enrique MARTINEZ, Francisco GIL, Inigo ZUBEROGOITIA, Jose Antonio MARTINEZ and Jose F. CALVO, Ardeola, 52(2), December 2005, 351-353