"- a, head of a (Polioptila nigriceps) Black-capped Gnat-catcher. b, head of a(Polioptila caerulea) Blue-gray Gnat-catcher. c, tail of (Polioptila nigriceps) Black-capped Gnat-catcher. d, tail of (Polioptila plumbea) Plumbeous Gnat-catcher" Elliot Coues, 1884

Black-capped Gnat-catcher

"- a, head of a (Polioptila nigriceps) Black-capped Gnat-catcher. b, head of a(Polioptila caerulea)…