11. Inner web of outer tail feather with a distinct white spot (12) — without 



a white spot (33) 



12. Plain black and white with a broad white median crown- 

 stripe Black and White Warbler. 



12. Not plain black and white, or if so, crown wholly black or dark (13) 

 13. Rump yellow (14) — not yellow (17) * 



14. White on tail in middle, extending equally over all but middle 

 pair of feathers Magnolia Warbler. 



14. White on tail near tip, or else occupying most of feathers .... (15) 

 15. Crown black, cheeks chestnut; below yellow, streaked with black in 



adult Cape May Warbler. 



15. Crown and sides of breast more or less yellow; cheeks black or dark blue 

 (16) 



16. Throat white — Myrtle Warbler — yellow Audubon Warbler. 



17. Wing with a white. patch at base of primaries; male, bluish above and 



white below, with cheeks, sides and throat black; female, olive above, 



yellowish below Black-throated Blue Warbler. 



17. Wing without such a white patch (18) 



18. Throat and chest black or partly black (19) — without black (20) 



19. Cheeks mostly blackish Townsend Warbler. 



19. Cheeks mostly yellow Black-throated Green Warbler. 



20. Wings with two distinct bands, sometimes joined to form a patch 



(21) 



20. Wings not banded or with but one band (31) 



21. Upper parts not 'grayish blue (22) 



21. Upper parts light grayish blue Cerulean Warbler, male. 



22. A light line over eye (23) — no light line over eye (26) 



23. Throat white or yellowish white, no yellow on sides of head; above pale 

 greenish blue Cerulean Warbler, female. 



23. Throat yellow, orange, or buff, or else sides of head mostly yellow. . . (24) 

 24. Back plain slate-gray in adult, grayish brown in young; cheeks 



and forehead black Sycamore Warbler. 



24. Back neither gray nor plain grayish brown (25) 



25. Back in male black and throat orange; in female streaked, throat yel- 

 lowish ( Blackburnian Warbler. 



25. Ba>ck olive-green; throat wholly yellow. . . . Townsend Warbler, young — 

 throat not wholly yellow Black-throated Green Warbler, young. 



i 26. Back more or less streaked (27) — plain olivaceous; below greenish 

 yellow Pine Warbler. 



27. Sides of crown or space behind eye, black (30) 



27. Sides of crown not black (28) 



28. Under tail-coverts white (29) 



28. Under tail-coverts buff < Bay-breasted Warbler, young. 



29. Sides of head, sides, and flanks unstreaked gray -. 



Chestnut-sided Warbler, young. 



29. Sides of head, sides, and flanks olive or streaked 



Black-poll Warbler, young. 



