Mobbing behavior and fatal attacks on snakes by Fasciated Antshrikes (Cymbilaimus lineatus)

Abstract

Birds often mob potential predators, which alerts other prey individuals of the danger and drives the predator away. Participation in, or increased intensity of mobbing is often associated with breeding activity suggesting an important function in the defense of nests and young. Less is known about bird mobbing of snakes, however, although these are important predators of birds, particularly at nests in tropical forests. Here, we report observations of mobbing behavior, some escalating into fatal attacks, of snakes by individuals of a tropical bird species, the Fasciated Antshrike (Cymbilaimus lineatus). In addition, we conducted snake-model presentations when Fasciated Antshrike pairs had active nests, and when not nesting, to examine the extent that pairs maintain a mobbing response outside of the nesting period. Pairs approached the snake model on average within 59 s (range 15–120 s) and 0.9 m (0.1–5 m) with no difference with nesting status. Our observations of mobbing behavior and fatal attacks suggest that passerines can also present a threat to potential snake predators and that mobbing is likely important in influencing predation rate. Mobbing when not nesting may be important in predator deterrence in bird species with year-round residency, and could influence territory quality and reproductive success. Forest birds that hunt large insects or other potentially dangerous prey may have morphological and cognitive specializations that help them to effectively mount a successful attack against predatory snakes.