Many tyrant flycatchers have loud vocalizations. The largest are usually quite vocal; their voices may be loud and rough or soft and melancholic, depending on the species. Continuous calls are generally heard only at dawn. A few species repeat the twilight song at the end of the day. The birds rarely call or sing in full daylight except during courtship or territorial dispute. The twilight song is generally given for several minutes almost without interruption. The large sulphur-bellied flycatcher (Myiodynastes luteiventris) and related species sing at dawn in sweet, melodious tones, which contrast with the shrill calls they utter later in the day. Studies

The feathers of this royal flycatcher (Onychorhynchus coronatus) make a distinctive display. (Photo by Doug Wechsler/VIREO. Reproduced by permission.)
Flight for catching prey differs between the willow flycatcher (Empidonax traillii) (top) and the kingbird (Tyrannus tyrannus) (bottom). (Illustration by Wendy Baker)

with a few North American tyrannids suggest that their calls are innate rather than learned.

A few species perform display flight. At dusk, the lesser elaenia (Elaenia chiriquensis) flies up steeply from thickets where it spends the day and sings a short, rough-sounding song until it is above the crowns of the trees. It then makes a steep dive into the bushes and becomes silent for the night. Spectacular courtship displays also take place in flight in some species. The western kingbird (Tyrannus verticalis) male flies straight upward for up to 50 ft (15 m) and then flings himself back downward, tumbling wildly.

The name tyrant is derived from the kingbirds, which boldly attack raptors and other enemies, such as snakes or squirrels, in defense of their nesting territory. Only rarely do kingbirds molest their smaller neighbors. Male tyrannids also protect their territory against birds of the same species, and two species may enter into disputes when their ranges overlap. During an aggressive chase, tyrannids typically fly above an intruder, pecking and sometimes clawing at its back.

Tyrant flycatchers that nest in the tropics are generally resident, while most North American flycatchers are migrants. Most tyrant flycatchers migrate at night, but a few, including the western kingbird, the eastern kingbird, and the scissor-tailed flycatcher, sometimes fly southward during the day. The eastern kingbird travels thousands of miles during migration, sometimes in flocks of dozens to hundreds. When over-water crossings are delayed by rough weather, huge flocks gather along coastlines to await more favorable conditions. In late August 1964, a flock of an estimated one million eastern kingbirds was reported off Florida.

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