Evolving Chats and Thrashers

     Several kinds of birds nest in dense thickets in hedgerows and woodland edges in southeastern Pennsylvania, as elsewhere in the eastern half of the United States.  Those species include northern cardinals, blue grosbeaks, gray catbirds, brown thrashers, white-eyed vireos, yellow-breasted chats and others.  Those thickets offer excellent shelter, and food in the forms of invertebrates and berries.  And of all the bird species that raise young in those jungles of shrubbery and vines, chats and thrashers have the more intriguing life histories.
     Chats are far more often heard than seen because of the males' unique vocalizations and bizarre actions to establish nesting territories and attract mates for rearing offspring.  Male chats utter whistles, clucks, toots and other strange notes, as well as pleasant songs.  And male chats repeatedly rise from thickets in floppy, attention-getting flight, while singing, then drop back into the shrubbery. 
     With the genders being similar, chats are pretty birds, being olive-brown on top and bright-yellow below.  They winter in Central America.
     The chats' ancestry is the most interesting thing about them.  They seem to be made of traits and parts leftover from other families of birds.  They have been considered to be a New World wood warbler, but they are not a warbler.  Currently, they are classified as a member of the blackbird/oriole family.  Chats, however, are in a genus of their own because they are so unique.  And over millenia, they may diverge into other species.
     In many of their habits, chats resemble the mimidae family of birds, which includes mockingbirds, catbirds and thrashers.   Chats skulk in the shadowed jungles of shrubs and vines like minidae.  And they sing similarly to northern mockingbirds, including at night, and imitating other birds' sounds.
     Chats often display the postures of North American cuckoos, kind of bent over with long tails drooping.  But, apparently, chats are not members of the mimidae or the cuckoo families.  Perhaps chats resemble those families because they share habitats- convergent evolution that shapes critters from different families into similar beings to cope with their environment in common. 
     Over future millenia, brown thrashers could be roadrunner-like, a species related to North American cuckoos.  Those thrashers are built like roadrunners, but smaller, and have strong legs for running after prey, as roadrunners do.
     I have seen brown thrashers, on foot, chasing after insect prey under thickets and across short-grass lawns.  They always remind me of small, brown roadrunners.
     Three closely related kinds of thrashers that live in deserts in southwestern North America, Leconte's, California and Crissal thrashers, are already roadrunner-like.  Roadrunners, too, live in deserts where they run down lizards, snakes, mice and invertebrates.  Those three kinds of thrashers seldom fly, but run fast enough, with their tails erect, to catch invertebrates and small snakes and lizards.  These desert thrashers, through millenia, developed stronger, faster legs because the swiftest ones caught prey and survived, as roadrunners must have done.  Maybe, some day, brown thrashers of the east will be more roadrunner-like.
     Yellow-breasted chats and brown thrashers already are interesting species.  And they may evolve into ever more intriguing kinds of birds, as can any other form of life on Earth.