The Tyrannidae family includes many species that look quite different from one another. However, certain physical characteristics are shared by the family as a whole. Tyrannidae are small to medium-sized, ranging from 3.5 to 11 inches (9 to 28 cm) in length—excluding tail streamers. They are usually simply colored, with shades of olive-green, gray, and brown on top and lighter colors (pale yellow, beige, and whitish) on the underparts. A few tyrannids are more brightly colored; the male vermilion flycatcher (Pyrocephalus rubinus) has a bright red crown and underparts. Several species of kingbird have bright yellow breasts. The kiskadees have a bright red, orange, yellow, or white spot on the crown that is visible only when the feathers are erected or spread out in excitement. The royal flycatcher (Onychorhynchus coronatus) performs perhaps the most spectacular visual display among tyrannids. This species has a crest that is hardly visible when not erected. When courting, however, the male's crest becomes erect, and the forehead appears surrounded by a widespread crown embedded with brownish-purple and velvety-black dots. The female's crest is almost as wide but paler.
The Tyrannid bill is generally short, wide, and slightly hooked at the tip; this characteristic distinguishes the family from most other passerines. The size of the bill varies with a species' food preference. Species that capture small insects like gnats and midges have a short bill, and those that eat larger insects like dragonflies, bees, and beetles are endowed with a longer, sturdier bill. In most species, bills are equipped with stiff rictal bristles (modified feathers), presumably to help direct flying insects into the open bill. Studies in the 1990s challenged this assumption. In experiments, flycatchers whose rictal bristles were either clipped off or taped back were just as adept at catching insects as their counterparts with intact bristles. A new hypothesis is that the bristles may help prevent insects from entering the eyes on collision with the bird.
Tyrannids' third and fourth toes are joined along the most basal segment, and there are horny plates on the outer side of the tarsus.
The tail consists usually of 12 feathers but sometimes 10, and varies in shape from square to graduated and forked. Tyrannus has greatly elongated central tail feathers. The fork-tailed flycatcher (Tyrannus savana) and the scissor-tailed flycatcher (Tyrannus forficata) measure up to about 6 in (16 cm) in length, but when the tail is included these birds measure an impressive 14 in (36 cm) from the head to the tip of the tail feathers.
The sexes are visually similar, although the female is paler in many species. Young resemble adults, although in species that sport brighter colors, adults are brighter and more colorful.
The willow flycatcher (Empidonax traillii) builds cup-shaped nests, the great kiskadee (Pitangus sulphuratus) builds globular-shaped twig nests, and the rose-throated becard (Pachyramphus aglaiae) builds a nest that hangs from a branch. (Illustration by Wendy Baker)
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