ズグロブユムシクイ Polioptila nigriceps

Long-tailed little bird of dry forest and scrub in northwest Mexico. Found as singles, pairs, or family groups, usually foraging at low to middle levels. Breeding plumage male (March–August) has black cap, but other plumages very similar to Blue-gray Gnatcatcher, a common migrant throughout the range of Black-capped. These species best separated by call note: Black-capped has lower and rougher call than mew of Blue-gray. Also note Blue-gray often has a pinkish base to its smaller bill (gray on Black-capped), a more distinct white eyering (face a little more "open" on Black-capped), and a shorter, less strongly graduated tail.