Anomalous binocular vision in African Harrier-Hawks.

An animal's visual field is the three-dimensional space around its head from which it can extract visual information at any instant. Bird visual fields vary markedly between species, and this variation is likely to be driven primarily by foraging ecology. The binocular visual field is the region in which the visual fields of the two eyes overlap; thus, objects in the binocular field are imaged by both eyes simultaneously.

The fast and forceful kicking strike of the secretary bird.

The study of animal locomotion has uncovered principles that can be applied to bio-inspired robotics, prosthetics and rehabilitation medicine, while also providing insight into musculoskeletal form and function [1-4]. In particular, study of extreme behaviors can reveal mechanical constraints and trade-offs that have influenced evolution of limb form and function [1,2]. Secretary birds (Sagittarius serpentarius; Figure 1A) are large terrestrial birds of prey endemic to sub-Saharan Africa, which feed on snakes, lizards and small mammals [5].