DIVERGING BIRD FAMILIES

      The species of two families of North American breeding birds, five kinds of flycatchers, that are nearly identical, and four of spot-breasted thrushes, that look much alike, are examples of species diversion from a common ancestor.  Each species of each family still resembles its close relatives, even after an apparent, long time lapse.  Each kind of bird in both families diverged from its ancestor and adapted to a different habitat to take advantage of new food and shelter sources, different than that of their close relatives.  That diverging from a common ancestor reduces competition for food and cover among those cousins, and creates new species.  

     Willow, alder, least, Acadian and yellow-bellied flycatchers of the Empidonax genus demonstrate quite well their diversion from a common ancestor.  All five of these species are plain brown for the most part, and have eye rings and wing bars.  They all are plain to be camouflaged among dense foliage. They all catch and eat flying insects in mid-air and feed those insects to their young.  They are identified by their songs, and the habitats they nest in.  

     But even these flycatchers' songs are similar, being short and not musical.  But those songs still repel other males of each bird's kind, and attracts females to the calling males for raising young.  Willow flycatchers nest in hedgerows between fields and males utter a sneezy "fitz-bew".  Alder flycatchers raise young in alder swamps and wet thickets along streams and males sing "fee-bee-o".  Least flycatchers rear offspring in open woods and their songs are a staccato "che-bec".  Acadian flycatchers hatch young in deciduous woods.  Many build open cups of grasses on American beech limbs extending over streams.  Males utter an explosive "pit-seee".  And yellow-bellied flycatchers breed in coniferous woods.  Males utter "chu-weee".  

     The four kinds of spot-breasted thrushes, gray-cheeked, Swainson's, hermit and veery, have brown feathering on top, which camouflages them when scratching for invertebrates on dead-leaf carpeted forest floors.  And they all have white underparts, with streaks of dark dots.  

     The males of these thrushes sing ethereal songs that are somewhat similar.  Their songs are so wonderfully beautiful that I think they come directly from God.  How can a mere bird broadcast such lovely music, designed only for themselves in the middle of woodlands?  

     All spot-breasted thrushes' songs sound breezy and flute-like, which indicates again a common ancestry.  Gray-cheeked thrushes emit a beautiful, rising "wheeo-wheeo-titi-wheee" from boreal forests.  Swainson's thrushes' songs, niches and appearance are almost the same as those of the gray-cheeked thrushes, possibly indicating fairly recent diversion from each other.  The songs of hermit thrushes are composed of three or four piping, ethereal phrases, each one starting with a long clear note, deep in mixed coniferous/deciduous forests.  Veeries' breezy songs wheel downward, "vee-uur, vee-uur, vee-uur, veer, veer" in the midst of bottomland, deciduous woods.

     The flycatcher and thrush species discussed here each have close cousins derived from a common ancestor.  New species are developing now that we don't know about.  Living beings are always fluid, always changing, to survive amid changing conditions, in the past, now, and into the future.