In vivo bite force in lovebirds (Agapornis roseicollis, Psittaciformes) and their relative biting performance among birds

Abstract

AbstractBite force represents a critical measure of an animal's feeding capabilities and has been analyzed in the context of ecology and body size in numerous vertebrate lineages. Among birds, bite force potential has been comprehensively quantified in finches; however, no in vivo data have been reported within parrots (order: Psittaciformes), and an anatomical estimate of bite force has been calculated for only two species. Despite this paucity of data, the parrot feeding system represents one of the most functionally interesting among tetrapods, exhibiting many anatomical novelties unique among birds and contributing to locomotion when parrots climb vertical surfaces. Within this study, we present in vivo bite force data from six rosy‐faced lovebirds (Agapornis roseicollis) at a range of gapes (2.5–10 mm, or 20–50°). These data are contextualized against more than 70 other avian taxa for which bite forces have been previously reported. Our findings demonstrate that bite forces decreased iteratively with each increase in gape size, with all between‐group differences yielding statistical significance. Relative to other birds, Agapornis, Psittacus, and Myiopsitta all exhibit larger bite forces than would be expected for their body size. We infer that the diet of parrots – many of which are specialized granivores, capable of crushing large and mechanically resistant seeds – may have contributed to their relatively strong biting capabilities. This interpretation is supported by other recent studies highlighting how the mechanical properties of foods drive bite forces in other vertebrate lineages, such as lizards and bats.