Pauses in a fast-paced life: Intermittent hovering in hummingbirds

Hummingbirds are known for sustained hovering powered by rapid and continuous wingbeats. Here, we describe and quantify a novel flight behavior, intermittent hovering, in which hovering hummingbirds momentarily pause their wing motion mid-air but maintain their vertical position in space, keeping their wings fully extended at the end of the upstroke. We present the first systematic account of flap-pauses and wing coloration across hummingbirds, and evaluate potential morphological and ecological correlates, as well as evolutionary patterns in the expression of this behavior. Slow-motion footage from 86 species spanning all nine major hummingbird clades shows that at least 45 species exhibited flap-pauses during sustained hovering. Phylogenetic comparative analyses revealed that hovering pauses are evolutionarily conserved and significantly associated with both greater body mass and longer wings. Furthermore, we found that the 16 species in our study with colored underwings also exhibit significantly longer wings. The convergence of intermittent hovering, wing elongation, and chromatic traits leads us to hypothesize that this flight behavior plays a role in visual and/or auditory communication.