出典:Wiktionary
From birds pecking at horse dung, originally US Army slang, 1940s[1].
for the birds (not comparable)
the birds alighted
a bird that seasonally migrates
birds that flock together
A bird alights―settles―on the ground or a tree.
走鳥類 《ダチョウ・ヒクイドリなど》.
鳥のひな
A bird migrates.
to aim at a bird―draw a bead on a bird