The initial idioms of the letter B

bird of (one's) own brain	bird watcher
birdbrain	birdbrained
bird-brain	bird-dog
birdie	birds and the bees, the
bird's eye view	Birds in their little nests agree
birds of a feather	birds of a feather (flock together)
Birds of a feather flock together	bird of passage
birdseed	bird's-eye view
birdturd	birdy
birthday suit	birthday
birth	birthright
biscuit	bishop
bison	bit
bit by bit	bite (someone) in the arse
bit much	bit of fluff