Reversed size dimorphism in birds of prey, especially in Tengmalm's Owl Aegolius funereus: a test of the "starvation hypothesis"

摘要: Suggestions and predictions of hypotheses (especially those the "starvation hypothesis") concerning reversed sexual size dimorphism birds prey were tested using field data collected in western Finland. Early breeding species two communities more dimorphic weight than late-breeding ones. The degree between mates 20 pairs Tengmalm's Owl correlated negatively with timing egg-laying, while wing length males positively laying date their partners. Clutch number young produced decreased within owl pairs. Data from Finnish owls did not support hypothesis that need to defend nest has caused evolution larger females, but partly agreed hypothesis", which states selection acts on females withstand food shortage season. It seems female Owls chose light, shortwinged because aerial agility; these probably competed efficiently for good territories nest-holes also hunted effectively economically. Because agility, tended catch less mammals females. This niche separation may reduce intersexual competition select high dimorphism.