Why female birds of prey are larger than males

摘要: The causes of the reversed sexual size dimorphism (RSD; females larger than males) in birds prey are subject to a centuries-old, passionate debate. A crucial difficulty is distinguish whether postulated benefits derive from proposed causal process(es) or incidental. After reviewing existing literature, we present methodology that overcomes this and renders unnecessary any speculative priori distinctions between evolved function incidental effects. We can thus justify following novel version well-known nest defence hypothesis as most likely explain phenomenon all show RSD: if female predominates actively defending eggs young against predators, then she heavier sex, her relatively greater body mass adaptive. That is, favoured (independently by natural selection. attractiveness it has potential raptors exhibiting RSD, deal with exceptional cases group, explains direction dimorphism, focuses on key factor reproductive success raptors, parsimonious, i.e. does not require supporting hypotheses, supported substantial evidence.