Reversed sexual dimorphism and prey size taken by male and female raptors: A comment on pande and dahanukar (2012)

Barn Owls; Tyto alba; reversed sexual dimorphism. Pande and Dahanukar (2012) studied foraging behavior of Barn Owls (Tyto alba) in India, a species with males smaller than females. Mean mass of the prey items brought by males in each of seven pairs was significantly less than mean mass brought by females, which the authors corre-lated with morphometric measurements of male and fe-male owls. However, male owls made significantly more prey deliveries than did females. The authors concluded that food-niche partitioning between the sexes may exist to reduce intersexual food competition; this supports the the-ory of reproductive role division as a possible explanation for Reversed Sexual Dimorphism (RSD) in raptors. Storer (1966) and Reynolds (1972) stressed niche sepa-ration in their theories of RSD, arguing that male accipi-ters in the United States took, on average, smaller, more abundant prey (Eltonian Pyramid, Krebs 2008) than did females. This seems to hold for some accipiters, e.g., Eur-asian Sparrowhawks (Accipiter nisus) in Great Britain (New-ton (1986). However Pande and Dahanukar (2012) used a study of Eurasian Sparrowhawks in Norway (Eldegard et al. 2003) to support their argument that males take smaller prey than females but Eldegard et al. found no differences in prey size taken by males and females; they did find differences in delivery rates between males and females