Variable plumage and bare part colouration in the Brown Falcon, Falco berigora: the influence of age and sex

摘要: The Brown Falcon, Falco berigora, is one of Australasia's most common raptors, yet considerable confusion remains over the influence geography, age and sex on plumage bare part colouration in this species. To address issue, 160 immature adult falcons from an individually marked, closely monitored population were examined. In contrast to previous studies, all known sex, age-group resident or their offspring. Adult males had significantly lighter upperpart, cap, ventral underwing covert comparison with other birds, resembling what has previously been described as a 'rufous morph'. Immature females darker than ages sexes upperpart plumage, descriptions 'dark morphs'. contrast, tended be similar intermediate between these extremes, 'brown buff-tinged, not white, separated them females. Cere orbital ring colour also differed age: dullest facial parts brightest, again being two. results indicate that variation observed could attributed differences opposed racial clines existence morphs. Moreover, brighter colours may function honest signals quality.