Convergent acquisition of a specialized feeding strategy: flush-pursue foraging in birds

Abstract

Birds exhibit diverse foraging strategies shaped jointly by the morphology and behaviour of predators and prey, as well as by habitat conditions. Some foraging tactics may result from convergent evolution when similar patterns among these factors are found across different lineages. Flush-pursue foraging, where birds use conspicuous wing and tail displays to startle hidden prey and pursue it, is known to drive plumage evolution among birds. However, the diversity and evolutionary relationship of the species using this strategy and associated traits remain poorly documented. For the first time, we compiled a global list of flush-pursuing species and conducted a family-level phylogenetic analysis. We found that flush-pursue foraging has independently evolved in four avian orders, and at least 17 families within Passeriformes, illustrating convergent adaptations to a specialized foraging niche. Flush-pursuers were more likely to be found in families with traits related to pursuit ability, such as smaller body size and longer tarsus length relative to body mass. This foraging strategy was also associated with denser habitats, likely providing various substrates and hiding spots for prey, and thus flushing prey makes foraging more efficient. Similarly, families with broader latitudinal ranges that cover more diverse habitats and prey types were also associated with a higher likelihood of flush-pursue behaviour. Family-level invertivorous diet predicted the presence of flush-pursuers, as expected from the susceptibility of arthropod sensory systems to startle displays. These findings illustrate how convergent acquisition of this unique foraging strategy of birds is shaped by the combination of morphology and ecology.