Phylogenetic analyses support flush-pursuit foraging and flocking behaviors as evolutionary drivers of flash plumage signals in North American passerines.

This article investigates the evolutionary drivers of "flash" plumage signals—color patches on birds that are hidden when still but revealed during movement—across 326 species of North American passerine birds. Using phylogenetically controlled analyses, the study tests three main hypotheses: that flash signals evolve to promote flocking behaviors, result from social or sexual selection, or coevolve with foraging strategies and diet. Results show that flash patches are common (present in 54% of species), predominantly white on wings and tails, and that rump flash patches are associated with winter flocking, migration, and plant-based diets, suggesting a role in flock cohesion or species recognition. Additionally, wing and tail flash patches correlate with a flush-pursuit foraging strategy, while no evidence supports social or sexual selection as broad drivers of flash signal evolution. The findings highlight natural selection related to flocking and foraging as key factors shaping the evolution of conspicuous flash plumage in these birds.