Reversed Sexual Size Dimorphism in Birds of Prey: Revival of an Old Hypothesis

Previous evidence from a few species suggests that raptor RSD may have evolved by sexual selection through competition among males for a territory, or among females for the best males or territories.

“This finding extends previous evidence, derived from only a few species, that raptor RSD may have evolved by sexual selection through competition among males for a territory (Widén 1984), or among females for the best males or territories (Sergio et al. 2007;McDonald et al. 2005;Pérez-Camacho et al. 2015).”

In species equipped with harmful weapons like talons, agility is more important than size and strength, where agility is defined as manoeuvrability and the ability to ascend rapidly to take an advantageous position above the opponent.

“In species equipped with harmful weapons like talons, agility is more important than size and strength, where agility is defined as manoeuvrability and the ability to ascend rapidly in order to take up an advantageous position above the opponent (Widén 1984).”

Disputes between males for ownership and delimitation of territories are solved by aerial displays and, ultimately, air fights.

“Disputes between males for ownership and delimitation of the territories are solved by aerial displays and, ultimately, air fights (Cade 1960;Andersson and Norberg 1981;Widén 1984).”