Fork-tailed Flycatcher

Tyrannus savana

Striking and conspicuous large flycatcher of savannas, grasslands, and other open country with scattered bushes and trees. All ages have black head and pale gray back, no pink in plumage as in the similar migrant Scissor-tailed Flycatcher. Adult tail is very long with lyre-shaped ribbons; juvenile has shorter tail but still looks distinctive. Perches on fences, low bushes, and even on the ground; at times in small flocks. Flight strong and direct, with tail sweeping behind. Some populations in South America are highly migratory, occasionally turning up far outside their normal range.

识别特征

The fork-tailed flycatcher is white below, gray above, and has a black cap. Males sometimes show a yellow crown stripe. Males also have an extremely long, forked tail, of even greater length than that of the related scissor-tailed flycatcher. Females have a somewhat shorter tail, and it is significantly shorter in juveniles. Males are 37–41 cm (15–16 in) in length; females, 28–30 cm (11–12 in), including tail. They weigh only 28–32 g (0.99–1.13 oz), much less than closely related kingbirds, which are half the total length of this species. The tail in adult males is two to three times longer than the length of the bird from the bill to the base of the tail. Generally, males and females of the species look quite similar, but can be distinguished by the longer tail in males.The nominate subspecies T. s. savana has a darker grey back compared to T. s. monachus and T. s. sanctaemartae, which have notable light backs that contrast greatly with their black heads. Discrete notches on the primary feathers are also quite handy in identifying subspecies.Most fork-tailed flycatchers are migratory, but some stay year-round, especially in southern Mexico. Migratory fork-tailed flycatchers tend to have more pointed wings than nonmigratory flycatchers.Fork-tailed flycatchers produce both vocal and nonvocal sounds. In general, they have a dry, buzzy call, and a weak "tic-note" while in flight.Their wings have been observed to make a distinct whistling note while flying overhead. In fact, research has been conducted involving distinct differences in the pitch of whistling noises by different subspecies of T. savana. This recent research has pointed towards a hypothesis that fork-tailed flycatchers are splitting into two distinct species, as the nonmigratory birds have a much-lower-pitched whistling note than the migrators. This becomes another observed difference amongst others (e.g. wing shape) pointing to the two-species conclusion.During mating displays, the males' wings may also make dry, crackling sounds; further research has investigated the use of these wing noises in potentially startling predators or would-be nest parasites (e.g. shiny cowbird).

分类信息

The fork-tailed flycatcher was described in 1760 by Mathurin Jacques Brisson under the French name "le tyran à queue fourchue" (lit. 'the fork-tailed tyrant') and then again in 1780 by Georges-Louis Buffon under the name "le savana" (because it lived in savannahs), but it was not until 1802 that François Marie Daudin coined the binomial name Tyrannus savana. The type locality is Suriname.Four subspecies are recognised:

学名: Tyrannus savana
命名信息: Daudin, 1802
目: Passeriformes
科: Tyrannidae
属: Tyrannus

分布与栖息地

Fork-tailed flycatchers are usually found below 1000 m elevation where they occur in a wide variety of habitats including pastures, riparian forests, forest edges, mangroves, and open residential areas with scattered trees. During migration, however, T. savana may be found in an even broader range of habitats.Its breeding range is from central Mexico to central Argentina. In most of this range, it is usually found year-round, but in the southern parts of its range, it retreats northward for the winter.During migration, fork-tailed flycatchers are quite gregarious, nesting in flocks of up to 10,000 individuals. This species is known to wander widely. It is spotted almost annually in the eastern United States seaboard and Canada, normally around fall (September–November).During migration, fork-tailed flycatchers have been observed flying accompanied by relative species such as eastern kingbirds and aggressively chasing off predators.The nominate subspecies, T. s. savana, is found in central and southern Brazil, Bolivia, Paraguay, Uruguay, and Argentina (south to the Río Negro), and overwinters in Amazonia, a large portion of northern South America (i.e., within the Orinoco River Basin), and Trinidad and Tobago, occasionally appearing in the West Indies.

迁徙: Complete migrants

行为

Migration pattern: Complete migrants.

保护状况

Population trend: stable.

种群趋势: stable

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