Richard Kenney's The Evolution of the Flightless Bird, the winning volume in the 1983 Yale Series of Younger Poets competition, was selected from among 650 entries in this annual competition.   All of one species whose origin is the sonnet, Kenney's poems ring many changes through that form, reflecting, as they do, a personal evolution in the poet's life. "The Hours of the Day"--the first of four chapters--is a long meditative sequence set in Vermont; here the square-shaped poems become the crown glass windowpanes of the farmhouse itself. "First Poems" follows next, a group of eight lyrics, ending with the poem that titles the book. "Heroes," a narrative quartet, with two poems from history and two from life, concerns itself with the shaping of all tales, from source to first telling. Finally, "Notes from Greece" chronicles certain thoughts and adventures there, notably a visit to the Byzantine monastic communities that ring the peninsula of Mt. Athos.   Born in Glens Falls, New York, in 1948, Richard Kenney received his B.A. from Dartmouth College in 1970. His poems have appeared in numerous magazines, including The New Yorker, The Atlantic Monthly, Hudson Review, American Scholar, Poetry, The Yale Review, Carolina Quarterly, and New England Review.