Template:Short description Template:Speciesbox
The chimney swift (Chaetura pelagica) is a bird belonging to the swift family Apodidae. A member of the genus Chaetura, it is closely related to both Vaux's swift and Chapman's swift; in the past, the three were sometimes considered to be conspecific. It has no subspecies. The chimney swift is a medium-sized, sooty gray bird with very long, slender wings and very short legs. Like all swifts, it is incapable of perching on flat surfaces, and can only perch on vertical surfaces. Many fly around all day and only come down at night when roosting.
The chimney swift feeds primarily on flying insects, but also on airborne spiders. It generally mates for life. It builds a bracket nest of twigs and saliva stuck to a vertical surface, which is almost always a human-built structure, typically a chimney; historically (before European colonists built chimneys), they nested in hollow trees (including old pileated woodpecker nest holes), a few still do so, though only rarely.<ref name = "HBW443"/> The female lays Template:Nowrap eggs. The altricial young hatch after Template:Nowrap and fledge a month later. The average chimney swift lives Template:Nowrap.
Taxonomy and systematicsEdit
When Carl Linnaeus first described the chimney swift in 1758, he named it Template:Nowrap, believing it to be a swallow.<ref name = "Fieldiana"/> This misconception continued well into the 1800s, with ornithologists calling it "American Swallow" (e.g. Mark Catesby)<ref name = "Feduccia"/> or "Chimney Swallow" (e.g. John James Audubon).<ref name = "Audubon"/> In 1825, James Francis Stephens moved this and other small, short-tailed New World swifts to the genus Chaetura, where it has since remained, although some authorities in the 1800s assigned it to a variety of now obsolete genera.<ref name = "Ridgway"/> It has no subspecies.<ref name = "Clements"/> The chimney swift's closest relative is Vaux's swift (C. vauxi). Scientists believe that the two species evolved from a common ancestor that was forced to North America's southeastern and southwestern corners by glacial advances. Separated for millennia by vast ice sheets, the survivors evolved into two species which are still separated by a wide gap across the continent's midsection.<ref name = "Newton"/> It is also closely related to the Chapman's swift (C. chapmani); in the past, the three were sometimes treated as a single species.<ref name = "HBW443"/>
The chimney swift's genus name, Chaetura, is a combination of two Ancient Greek words: chaite, which means "bristle" or "spine", and oura which means "tail". This is an apt description of the bird's tail, as the shafts of all ten tail feathers (rectrices) end in sharp, protruding points.<ref name = "Kyle15"/> The specific name pelagica is derived from the Greek word pelagikos, which means "of the sea".<ref name = "Helm"/> This is thought to be a reference to its nomadic lifestyle rather than to any reference to the sea,<ref name = "DunneHowTo"/> a theory strengthened by the later assignment of the specific name pelasgia (after the nomadic Pelasgi tribe of ancient Greece) to the same species by other ornithologists.<ref name = "Helm"/> Its common name refers to its preferred nesting site and its speedy flight.<ref name = "Fergus"/>
DescriptionEdit
This is a medium-sized swift, measuring from Template:Convert in length,<ref group="nb">By convention, length is measured from the tip of the bill to the tip of the tail on a dead bird (or skin) laid on its back.<ref name = "HBW"/></ref> with a wingspan of Template:Convert and a weight ranging from Template:Convert.<ref name = "Cornell"/> The sexes are identical in plumage,<ref name = "Johnston"/> though males average slightly heavier than females.<ref name = "Johnston"/> The adult's plumage is a dark sooty olive above and grayish brown below, with a slightly paler rump and uppertail covert feathers, and a significantly paler throat.<ref name = "Ridgely"/> Its upperparts are the most uniformly colored of all the Chaetura swifts, showing little contrast between back and rump.<ref name = "Chantler185"/> Its beak is black, as are its feet and legs. Its iris is dark brown.<ref name = "Barrows"/> The juvenile plumage (held by young birds for their first few months after fledging) is very similar to that of adults, but with whitish tips to the outer webs of the secondaries and tertials.<ref name = "NatWeb"/>
The chimney swift's wings are slender, curved and long,<ref name = "Dunne2"/> extending as much as Template:Convert beyond the bird's tail when folded.<ref name = "Blanchan"/> Its wingtips are pointed, which helps to decrease air turbulence (and therefore drag) during flight.<ref name = "Henderson"/> Its humerus (the bone in the inner part of the wing) is quite short, while the bones farther out (more distally) along the wing are elongated, a combination which allows the bird to flap very quickly.<ref name = "Sibley2"/> In flight, it holds its wings stiffly, alternating between rapid, quivering flaps and longer glides. Its flight profile is widely described as a "cigar with wings"—a description first used by Roger Tory Peterson.<ref name = "Dunne2"/> Although the bird often appears to beat its wings asynchronously during flight, photographic and stroboscopic studies have shown that it beats them in unison. The illusion that it does otherwise is heightened by its very fast and highly erratic flight, with many rapid changes of direction.<ref name = "Savile"/>
The legs of the chimney swift, like those of all swifts, are very short.<ref name = "Coues"/> Its feet are small but strong, with very short toes that are tipped with sharp, curved claws.<ref name = "Sibley2"/> The toes are anisodactyl—three forward, one back—like those of most birds, but the chimney swift can swivel its back toe (its hallux) forward to help it get a better grip. Unlike the legs and feet of most birds, those of the chimney swift have no scales; instead, they are covered with smooth skin.<ref name = "Kyle15"/>
Its tail is short and square,<ref name = "NatGeo"/> measuring only Template:Convert in length.<ref name = "Barrows"/> All ten of its tail feathers have shafts which extend as much as Template:Convert beyond the vanes, ending in sharp, stiff points.<ref name = "Kyle15"/> These help the bird to prop itself against vertical surfaces.<ref name = "Encyclopedia"/>
The chimney swift has large, deep set eyes. These are protected by small patches of coarse, black, bristly feathers, which are located in front of each eye. The swift can change the angle of these feathers, which may help to reduce glare. It is far-sighted and, like some birds of prey, this swift is bifoveal: each eye having both a temporal and a central fovea.<ref group="nb">For more information, see Anatomy of the eye section in the Bird vision article</ref> These are small depressions in the retina where visual acuity is highest,<ref name = "HBW5"/> and help to make its vision especially acute.<ref name = "Wood"/> Like most vertebrates, it is able to focus both eyes at once; however, it is also able to focus a single eye independently.<ref name = "HBW5"/>
Its bill is very small, with a culmen that measures a mere Template:Convert in length.<ref name = "Chantler187"/> However, its gape is huge, extending back below its eyes, and allowing the bird to open its mouth very widely.<ref name = "Americana"/> Unlike many insectivorous birds, it lacks rictal bristles at the base of the beak.<ref name = "Surface"/>
Similar speciesEdit
The chimney swift looks very much like the closely related Vaux's swift, but is slightly larger, with relatively longer wings and tail, slower wingbeats<ref name = "Sibley"/> and a greater tendency to soar.<ref name = "NatGeo"/> It tends to be darker on the breast and rump than the Vaux's swift, though there is some overlap in plumage coloring.<ref name = "Sibley"/> It can be as much as 30 percent heavier than Vaux's swift, and its wings, which are proportionately narrower, show a pronounced bulge in the inner secondaries.<ref name = "SibleyWeb"/> The chimney swift is smaller, paler and shorter tailed than the black swift.<ref name = "Sibley"/> In Central America, it is most similar to Chapman's swift, but it is paler (matte olive rather than glossy black) and has a stronger contrast between its pale throat and the rest of its underparts than does its more uniformly colored relative.<ref name = "Ridgely"/>
Distribution and habitatEdit
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A widespread breeding visitor to much of the eastern half of the United States and the southern reaches of eastern Canada, the chimney swift migrates to South America for the winter. It is a rare summer visitor to the western U.S,<ref name = "Kaufman"/> and has been recorded as a vagrant in Anguilla, Barbados, Greenland, Jamaica, Portugal, the United Kingdom and the U.S. Virgin Islands.<ref name=IUCN/> It is found over open country, savanna, wooded slopes and humid forests.<ref name = "Edwards"/>
The chimney swift's wintering grounds were only discovered in 1944, when bands from birds banded (ringed) in North America were recovered in Peru.<ref name = "Lincoln"/> An indigenous Peruvian had been wearing the bands as a necklace.<ref name = "Wilson"/>
BehaviorEdit
The chimney swift is a gregarious species, and is seldom seen alone. It generally hunts in groups of two or three, migrates in loose flocks of 6–20, and (once the breeding season is over) sleeps in huge communal roosts of hundreds or thousands of birds.<ref name = "Dunne2"/> Like all swifts, it is a superb aerialist, and only rarely seen at rest. It drinks on the wing, skimming the surface of the water with its beak.<ref name = "Wauer"/> It also bathes on the wing, gliding above the surface of a body of water, briefly smacking its breast into the water, then flying off again, shaking its feathers as it goes.<ref name = "Cornell"/> It has been recorded by pilots flying more than a mile above the surface of the earth, including one seen at Template:Convert.<ref name = "Williams"/> It is incapable of perching upright like most birds do; instead, it clings to vertical surfaces.<ref name="Sibley"/> If it is disturbed while at rest, the chimney swift will clap its wings loudly once or twice against its body; it does this either in place, or while dropping down several feet to a lower location. This behavior can result in a loud "thundering" sound if large roosts of the birds are disturbed. The sound is thought to be the bird's way of scaring away potential predators.<ref name = "Dexter3"/>
FeedingEdit
Like all swifts, the chimney swift forages on the wing.<ref name = "Cornell"/> Studies have shown that Template:Nowrap of its food items are flying insects, including various species of flies, ants, wasps, bees, whiteflies, aphids, scale insects, stoneflies and mayflies. It also eats airborne spiders drifting on their threads.<ref name = "Wauer"/> It is an important predator of pest species such as the red imported fire ant<ref name = "Whitcomb"/> and the clover root curculio.<ref name = "Webster"/> Researchers estimate that a pair of adults provisioning a nest with three youngsters consume the weight equivalent of at least Template:Nowrap insects per day.<ref name = "Woods"/> Like many bird species, the chimney swift periodically coughs up pellets composed of indigestible bits of prey items.<ref name = "Duke"/>
During the breeding season, at least half of the chimney swift's forays occur within Template:Convert of its nest; however, it ranges up to Template:Convert away.<ref name = "ON"/> While most of its food is seized following aerial pursuit, some is gleaned from the foliage of trees; the bird hovers near the ends of branches or drops through upper canopy levels.<ref name = "George"/> The chimney swift generally flies quite high, though it descends during cold or rainy weather.<ref name = "Crossley"/> When feeding, it regularly occurs in small groups, and sometimes hunts with swallows, particularly barn swallows and purple martins;<ref name = "Dunne2"/> in mixed-species flocks, it is typically among the lower fliers.<ref name = "Chantler187"/> There is at least one record of a chimney swift attempting to steal a dragonfly from a purple martin, and it has been observed chasing other purple martins.<ref name = "Brown"/> In general, it is a diurnal feeder which remains active into early evening. However, there are records, particularly during migration periods, of chimney swifts feeding well after dark over brightly lit buildings.<ref name = "Cottam"/>
The species shows two-weight peaks each year: one at the start of the breeding season, and a higher one shortly before it begins its migration south in the autumn. Its lowest weights are typically recorded during the breeding season, when it also begins a complete molt of its plumage. The chimney swift's weight gain before migration is smaller than that of some passerines, suggesting that it must refuel en route at various stopover points.<ref name = "Collins"/>
BreedingEdit
The chimney swift is a monogamous breeder which normally mates for life, though a small percentage of birds change partners.<ref name = "Dexter"/> Pairs perform display flights together, gliding with their wings upraised in a steep "V", and sometimes rocking from side to side. Breeding birds arrive as early as mid-March in the southern U.S., and late-April to mid-May in the Canadian provinces.<ref name = "NatWeb"/>
Before the arrival of European colonists into North America, the chimney swift nested in hollow trees; now, it uses human-built structures almost exclusively.<ref name = "Encyclopedia"/> While the occasional nest is still built in a hollow tree (or, exceptionally, in an abandoned woodpecker nest),<ref name = "WP"/> most are now found inside chimneys, with smaller numbers in airshafts, the dark corners of lightly used buildings, cisterns,<ref name = "Cistern"/> or wells.<ref name = "Rogers"/> The nest is a shallow bracket made of sticks, which the birds gather in flight, breaking them off trees. The sticks are glued together (and the nest to a vertical surface) with copious amounts of the bird's saliva.<ref name = "Baicich"/> During the breeding season, each adult's salivary glands more than double in size, from Template:Convert in the non-breeding season to Template:Convert during the breeding season.<ref name = "Johnston"/>
Unlike some swift species, which mate in flight, chimney swifts mate while clinging to a vertical surface near their nest.<ref name="Kyle38"/> They copulate daily, until the clutch is complete.<ref name = "Kyle39"/> The female typically lays Template:Nowrap,<ref name = "Baicich"/> though clutch sizes range from Template:Nowrap.<ref name = "Kyle39"/> The eggs, which are long and elliptical in shape, are moderately glossy, smooth and white, and measure Template:Convert.<ref name = "Baicich"/> Each weighs nearly Template:Nowrap of the female's body weight.<ref name = "Kyle39"/> Incubated by both parents, the eggs hatch after Template:Nowrap. Baby chimney swifts are altricial—naked, blind and helpless when they hatch. Fledglings leave the nest after a month.<ref name = "Baicich"/>
The average chimney swift's life span is Template:Nowrap,<ref name = "Dexter2"/> but one is known to have lived more than Template:Nowrap. It was originally banded as an adult, and was recaptured in another banding operation some Template:Nowrap later.<ref name = "BandingLab"/>
Predators and parasitesEdit
Mississippi kites, peregrine falcons and merlins are raptors that are known to take adult chimney swifts in flight, being among the select few avian hunters fast enough to overtake the appropriately named swift on the wing.<ref name = "Steeves"/> Eastern screech-owls have been seen attacking colonies, as have non-avian predators including eastern rat snakes, northern raccoons and tree squirrels. These are most likely to take nestlings but may take some nesting adults as well.<ref name = "Cink"/><ref>Laskey, A. R. 1946. Snake depredation at birds' nests. Wilson Bull. 58:217-218.</ref> When disturbed by potential predators (including humans) at the colony, adult chimney swifts slap their wings together after arching back and taking flight, making a very loud noise known either as "booming" or "thunder noises". When disturbed, nestlings make a loud, raspy raah, raah, raah sound. Both sounds seem designed to startle potential predators.<ref>Dexter, R. W. 1946. More concerning the thundering and clapping sounds of the Chimney Swift. Auk 63:439-440.</ref><ref>Fischer, R. B. 1958. The breeding biology of the Chimney Swift, Chaetura pelagica (Linnaeus). N.Y. State Mus. Sci. Serv. Bull. 368:1-139.</ref>
The chimney swift carries a number of internal and external parasites. It is the type host for the nematode species Aproctella nuda,<ref name = "Hamann"/> the feather mite species Euchineustathia tricapitosetosa,<ref name = "Mite"/> and the biting lice species Dennyus dubius,<ref name = "Ewing"/> and is also known to carry the tapeworm species Pseudochoanotaenia collocaliae.<ref name = "Manter"/> Its nest is known to host the Hemiptera species Cimexopsis nyctali, which is similar to the bed bug and can (on rare occasions) become a pest species in houses.<ref name = "Boyd"/><ref name = "UM"/>
VoiceEdit
{{#invoke:Listen|main}} The chimney swift has a twittering call, consisting of a rapid series of hard, high-pitched chirps. It sometimes gives single chirps.<ref name = "Sibley"/>
Conservation statusEdit
In 2010, the International Union for Conservation of Nature changed the chimney swift's status from least concern to near threatened. In 2018, the IUCN changed the chimney swift's status from near threatened to vulnerable. Although the global population is estimated at Template:Nowrap, it has declined precipitously across the majority of its range.<ref name=IUCN/> The causes of population declines are largely unclear, but may be related to the alteration of the insect community due to pesticide use in the early half of the 20th century.<ref name = "Nocera"/> In Canada, they were listed as threatened by COSEWIC for several years with a likely future listing as a Schedule 1 species of the Species at Risk Act. In the U.S., the chimney swift is protected by the Migratory Bird Treaty Act of 1918. Neither birds nor nests can be removed from chimneys without a federally-issued permit.<ref name = "MDR"/> Populations may have increased historically with the introduction of chimneys to North America by European settlers, providing plentiful nesting opportunities.Template:Citation needed
After sudden temperature drops, the chimney swift sometimes hunts low over concrete roads (presumably following insect prey drawn to the warmer road), where collisions with vehicles become more likely.<ref name = "Finnis"/> Severe storms, such as hurricanes, encountered during migration can seriously impact the chimney's swift's survival rates. Chimney swifts caught up in 2005's Hurricane Wilma were swept as far north as Atlantic Canada and Western Europe, including six reaching Great Britain, the most ever seen there in a single year.<ref name="BBRC">Template:Cite journal</ref> More than 700 were found dead. The following year, roost counts in the province of Quebec, Canada showed a decrease of 62 percent, and the overall population in the province was halved.<ref name = "Dionne"/>
History of observationEdit
In 1899, Mary Day of New Jersey observed a pair of chimney swifts nesting in a chimney, and noted the incubation period was 19 days. The first detailed study of chimney swifts began in 1915 by self-taught ornithologist Althea Sherman in Iowa. She commissioned a 28 foot tall tower, of a similar design to a chimney, with ladders and peep holes installed to facilitate observation. Chimney swifts nested in her tower, and for over fifteen years, she meticulously recorded her observations, filling over 400 pages.<ref name=Kyle>Template:Cite book</ref> Sherman remarked that although the tower had been designed with a limited knowledge of the nesting behavior of chimney swifts, after many years of observation she believed that the original design was ideal.<ref>Template:Cite book</ref>
NotesEdit
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ReferencesEdit
Cited textsEdit
External linksEdit
Template:Sister project Template:Sister project
- Birds of the World - Chimney Swift
- Chimney Swift Conservation Project—Driftwood Wildlife Association
- Ralph W. Dexter research on chimney swift
- Photos from Flickr's Field Guide Birds of the World
- Template:InternetBirdCollection
- Sound recording at Florida Museum of Natural History
- Template:Xeno-canto species
- Template:VIREO