Hawking (birds)
Encyclopedia
Hawking is a feeding strategy in bird
s involving catching flying insect
s in the air. The term usually refers to a technique of sallying out from a perch to snatch an insect and then returning to the same or a different perch. This technique is called “flycatching” and some birds known for it are several families
of “flycatchers”: Old World flycatcher
s, Monarch flycatchers, and Tyrant flycatcher
s. Other birds, such as swift
s, swallow
s, and nightjar
s, also take insects on the wing in continuous aerial feeding. The term “hawking” comes from the similarity of this behavior to the way hawks take prey in flight, although, whereas raptors may catch prey with their feet, hawking is the behavior of catching insects in the bill. Many birds have a combined strategy of both hawking insects and gleaning
them from foliage.
In hawking behavior, a bird will watch for prey from a suitable perch. When it spies potential prey, the bird will fly swiftly from its perch to catch the insect in its bill, then return to the perch or sometimes to a different perch. This maneuver is also called a "sally". Prey that is very small relative to the bird, such as gnats, may be consumed immediately while in flight, but larger prey, such as bees or moths, are usually brought back to a perch before being eaten. Sometimes the prey will attempt to escape and this can result in a fluttering pursuit before returning to the perch. Depending on the species
of bird, there are observable variations on this behavior. Some species, such as the Olive-sided Flycatcher
of North America and the Ashy Drongo
of South Asia, tend to choose an exposed perch, such as a dead tree branch overlooking a clearing, whereas others, such as the North American Acadian Flycatcher
and the Asian Small Niltava
perch within the cover of foliage deep in a forest or woodland habitat.
Many birds make use of a variety of tactics. A study of feeding behaviors in the family Tyrranidae categorized the following moves as ways of taking insect prey: aerial hawking (i.e. flycatching), perch-to-ground sallying, ground feeding (chasing after insects on the ground), perch-to-water sallying, sally-gleaning (can involve an hover-gleaning or a rapid strike), and gleaning while perched. Some tyrant flycatchers, such as those that choose a prominent perch from which to hawk insects, have more of a tendency to return to the same perch after each sally, while others, particularly those of the forest interior, show less of this tendency. A similar pattern is seen in Great Britain
, where there are but two flycatchers, the Spotted Flycatcher
and the Pied Flycatcher. The Spotted Flycatcher is the specialist, and tends to return to the same perch after each sally. The Pied Flycatcher is more of a generalist, gleaning as well as flycatching, and changes perches often.
Birds with the name "flycatcher" are not the only ones to engage in flycatching behavior. For example, Lewis's Woodpecker
feeds by flycatching. Some honeyeater
s of Australasia
employ hawking and gleaning as feeding tactics. Bee-eater
s catch bees in a similar manner and return to the perch to remove the sting before consuming. Furthermore, many small owl
s take insect prey on the wing; examples include the Western Screech Owl
of North America and the Brown Boobook
of Asia.
Continuous aerial feeding is a different way of hawking insects. It requires long wings and skillful flying, as in nightjars, swallows, and swifts. Swifts are the masters of aerial feeding; they can fly for hours without perching. Swallows, though similar to swifts in shape, are unrelated to swifts. Swallows feed in a similar manner to swifts, but less continuously, as they don't glide as much and they stop to perch for awhile between bouts of aerial feeding. This has to do with their prey: swifts fly higher in pursuit of smaller, lighter insects that are scattered by rising air currents, while swallows generally chase after medium-sized insects that are lower to the ground, such as flies. When swallows fly higher to go after smaller insects, they adjust their fight style to glide more, like a swift. Birds of the nightjar family employ a variety of moves for catching insects. The Common Nighthawk
of North America flies in swift-like fashion on its long, slender, pointed wings. The Common Poorwill
, on the other hand, flies low and perches low to the ground and will sally up into the air after insects. The Oilbird
of South America, a relative of nightjars, lives in caves and uses echolocation
to catch insects flying in pitch darkness.
, which mostly eats fruit but is also often observed hawking insects over streams; terns of the genus Chlidonias, such as the Black Tern
, fly in search of insects, sometimes chasing after dragonflies in flight; and even large owl
s that normally feed on rodents will snatch flying insects when the opportunity arises.
Flight
, especially flight driven by the muscle-powered flapping of wings, is a strenuous physical activity. Although a sally from a perch may look like a single, rapid movement to the human eye, actually the bird must perform several moves: it begins its take-off by pushing with its feet to get into the air, it flaps its wings to generate forward motion (thrust
), pursues the prey item, turns in the air, flies back, and, with a final flurry of wings, lands on its perch. When a bird hawks insects, the prey must be substantial enough to pay off in terms of a biological energy budget
. In other words, the bird must take in more energy in food than it is using up in the pursuit of food. Therefore, flycatchers tend to prefer insect prey of moderate size, such as flies, over smaller insects like gnats.
For birds that live in a forest habitat or other setting where short bursts of flight are used in sallies or for getting from tree branch to tree branch, their short, rounded wings are suitable for the rapid flapping required to maneuver in tight spaces. Birds in more open settings that sally after larger insects like bees, such as kingbird
s and bee-eaters, benefit from longer, more pointed wings, which are more efficient because they generate more lift
and less drag
. Swallows and swifts, which glide about in totally open spaces, have even longer wings. Another function of long, pointed wings is to enable these birds to turn quickly and smoothly in mid-glide. The wingtips create little vortices of air, within which the low air pressure creates additional lift on the wingtips. Furthermore, long, forked tails provide additional lift, stability, and steering ability, which is important for flying at slower speeds (swifts, though capable of flying very fast, actually must fly relatively slowly to intercept airborne insects). In fact, swifts have bodies so well adapted for flying that they are unable to perch on branches or land on the ground, and so they nest and roost on precipices such as rocky cliffs, behind waterfalls (as the Black Swift
of North America and the Great Dusky Swift
of South America are known to do) or in chimneys, as in the case of the Chimney Swift
.
Bill
size and shape is also important. Compared to the bills of birds specialized for gleaning, a relatively larger, broader bill is ideal for catching sizeable insects such as bees and flies. The presence of bristles near the bill (rictal bristles) in some flycatchers may be an adaptation for hawking insects; scientists are not sure of the function but they may help protect the eyes or they might actually help provide the bird sensory information as to the location of the prey. Swallows, swifts, and nightjars do not have large bills, but they have wide-gaping mouths. Some nightjars also have bristles around the bill (the Common Poorwill does, the Common Nighthawk does not).
When different kinds of birds have the same adaptations, such similarities are not necessaily indicative of any familial relationship between bird species. Rather, they are the result of convergent evolution
. Consider, for example, the marked resemblance in body size, shape, and coloration between flycatchers of several families, though these species are not closely related: the Asian Brown Flycatcher
(of the Muscicapidae or Old World flycatcher
family), Acadian Flycatcher
(of the Tyrranidae or Tyrant flycatcher
family) of the New World, and Slaty Monarch
(of the Monarchidae or Monarch flycatcher family), endemic to Fiji
. All three use flycatching to acquire some or all of their food. But these three families belong to separate branches of the evolutionary tree of songbird
s, which diverged in two branching events some 60 and 90 million years ago and continued to evolve independently in different parts of the world.
Likewise, the similarities of swifts and swallows once lead naturalists to conclude they were related, but it is now established that they are unrelated, and that the same lifestyle has led to the same adaptations.
in winter. Migration is timed to the availability of the birds' preferred food. For instance, it has been observed in Great Britain that migrating swallows arrive earlier in the spring than swifts, this correlates with the later profusion of small insects that swifts feed on. Weather also has an impact on the availability of flying insects. Swallows, for example, are obliged to go where the insects are, and depending on the weather they may adjust their choice of prey or be forced to seek out prey in different locations.
The preference for certain kinds of aerial insect as a food source seems to correlate with gregarious or colonial
behavior versus territoriality
. For birds that take advantage of swarming insects, which are by nature found in local concentrations, colonial breeding can be a successful strategy. An example is the Cliff Swallow
of western North America. Its relative the Barn Swallow
hunts larger, non-swarming insects, and is more solitary.
Certain neotropical tyrant flycatchers will join mixed-species foraging flocks, as will some Asian drongo
s. Such flocks stir up flying insects, which can then be picked off in quick sallies.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s involving catching flying insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s in the air. The term usually refers to a technique of sallying out from a perch to snatch an insect and then returning to the same or a different perch. This technique is called “flycatching” and some birds known for it are several families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of “flycatchers”: Old World flycatcher
Old World flycatcher
The Old World flycatcher family Muscicapidae is a large family of small passerine birds mostly restricted to the Old World. These are mainly small arboreal insectivores, many of which, as the name implies, take their prey on the wing.-Characteristics:...
s, Monarch flycatchers, and Tyrant flycatcher
Tyrant flycatcher
The tyrant flycatchers are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds on Earth, with more than 400 species. They are the most diverse avian family in every country in the Americas, except for the United States and...
s. Other birds, such as swift
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...
s, swallow
Swallow
The swallows and martins are a group of passerine birds in the family Hirundinidae which are characterised by their adaptation to aerial feeding...
s, and nightjar
Nightjar
Nightjars are medium-sized nocturnal or crepuscular birds with long wings, short legs and very short bills. They are sometimes referred to as goatsuckers from the mistaken belief that they suck milk from goats . Some New World species are named as nighthawks...
s, also take insects on the wing in continuous aerial feeding. The term “hawking” comes from the similarity of this behavior to the way hawks take prey in flight, although, whereas raptors may catch prey with their feet, hawking is the behavior of catching insects in the bill. Many birds have a combined strategy of both hawking insects and gleaning
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
them from foliage.
Flycatching
The various methods of taking insects have been categorized as: gleaning (perched bird takes prey from branch or tree trunk), snatching (flying bird takes prey from ground or branch), hawking (bird leaves perch and takes prey from air), pouncing (bird drops to ground and takes prey) and pursuing (flying bird takes insects from air).In hawking behavior, a bird will watch for prey from a suitable perch. When it spies potential prey, the bird will fly swiftly from its perch to catch the insect in its bill, then return to the perch or sometimes to a different perch. This maneuver is also called a "sally". Prey that is very small relative to the bird, such as gnats, may be consumed immediately while in flight, but larger prey, such as bees or moths, are usually brought back to a perch before being eaten. Sometimes the prey will attempt to escape and this can result in a fluttering pursuit before returning to the perch. Depending on the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of bird, there are observable variations on this behavior. Some species, such as the Olive-sided Flycatcher
Olive-sided Flycatcher
The Olive-sided Flycatcher, Contopus cooperi, is a passerine bird. It is a medium-sized tyrant flycatcher.- Description :Adults are dark olive on the face, upperparts and flanks. They have light underparts, a large dark bill and a short tail....
of North America and the Ashy Drongo
Ashy Drongo
The Ashy Drongo is a species of bird in the drongo family Dicruridae. It is found widely distributed across South and Southeast Asia with several populations that vary in the shade of grey, migration patterns and in the size or presence of a white patch around the eye.-Description:The adult Ashy...
of South Asia, tend to choose an exposed perch, such as a dead tree branch overlooking a clearing, whereas others, such as the North American Acadian Flycatcher
Acadian Flycatcher
The Acadian Flycatcher is a small insect-eating bird of the tyrant flycatcher family.- Description :Adults have olive upperparts, darker on the wings and tail, with whitish underparts; they have a white eye ring, white wing bars and a wide bill. The breast is washed with olive. The upper part of...
and the Asian Small Niltava
Small Niltava
The Small Niltava is a species of bird in the Muscicapidae family.It is found in Bangladesh, Bhutan, China, India, Laos, Myanmar, Nepal, Thailand, and Vietnam. Its natural habitat is subtropical or tropical moist montane forests.-References:* BirdLife International 2004. . Downloaded on 26...
perch within the cover of foliage deep in a forest or woodland habitat.
Many birds make use of a variety of tactics. A study of feeding behaviors in the family Tyrranidae categorized the following moves as ways of taking insect prey: aerial hawking (i.e. flycatching), perch-to-ground sallying, ground feeding (chasing after insects on the ground), perch-to-water sallying, sally-gleaning (can involve an hover-gleaning or a rapid strike), and gleaning while perched. Some tyrant flycatchers, such as those that choose a prominent perch from which to hawk insects, have more of a tendency to return to the same perch after each sally, while others, particularly those of the forest interior, show less of this tendency. A similar pattern is seen in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, where there are but two flycatchers, the Spotted Flycatcher
Spotted Flycatcher
The Spotted Flycatcher, Muscicapa striata, is a small passerine bird in the Old World flycatcher family. It breeds in most of Europe and western Asia, and is migratory, wintering in Africa and south western Asia. It is declining in parts of its range....
and the Pied Flycatcher. The Spotted Flycatcher is the specialist, and tends to return to the same perch after each sally. The Pied Flycatcher is more of a generalist, gleaning as well as flycatching, and changes perches often.
Birds with the name "flycatcher" are not the only ones to engage in flycatching behavior. For example, Lewis's Woodpecker
Lewis's Woodpecker
The Lewis's Woodpecker, Melanerpes lewis, is a large North American species of woodpecker which was named for Meriwether Lewis, one of the explorers who surveyed the areas bought by the United States of America during the Louisiana Purchase.-Description:...
feeds by flycatching. Some honeyeater
Honeyeater
The honeyeaters are a large and diverse family of small to medium sized birds most common in Australia and New Guinea, but also found in New Zealand, the Pacific islands as far east as Samoa and Tonga, and the islands to the north and west of New Guinea known as Wallacea...
s of Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
employ hawking and gleaning as feeding tactics. Bee-eater
Bee-eater
The bee-eaters are a group of near-passerine birds in the family Meropidae. Most species are found in Africa and Asia but others occur in southern Europe, Australia, and New Guinea. They are characterised by richly coloured plumage, slender bodies, and usually elongated central tail feathers...
s catch bees in a similar manner and return to the perch to remove the sting before consuming. Furthermore, many small owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
s take insect prey on the wing; examples include the Western Screech Owl
Western Screech Owl
The Western Screech Owl is a small owl native to North and Central America, closely related to the European Scops owl and the North American Eastern Screech Owl. The scientific name commemorates the American naturalist Robert Kennicott.-Description:Length averages , wingspan and weight . Weight...
of North America and the Brown Boobook
Brown Hawk Owl
The Brown Hawk-Owl is an owl which is a resident breeder in south Asia from India and Sri Lanka east to western Indonesia and south China....
of Asia.
Sustained-flight feeding
Common Nighthawk
The Common Nighthawk is a medium-sized crepuscular or nocturnal bird, whose presence and identity are best revealed by its vocalization. Typically dark , displaying cryptic colouration and intricate patterns, this bird becomes invisible by day. Once aerial, with its buoyant but erratic flight,...
of North America flies in swift-like fashion on its long, slender, pointed wings. The Common Poorwill
Common Poorwill
The Common Poorwill is a nocturnal bird of the family Caprimulgidae, the nightjars. It is found from British Columbia and southeastern Alberta, through the western United States to northern Mexico...
, on the other hand, flies low and perches low to the ground and will sally up into the air after insects. The Oilbird
Oilbird
The Oilbird , also known as Guácharo, is a bird found in the northern areas of South America . They are nocturnal feeders on the fruits of the Oil Palm and tropical laurels, and are the only nocturnal fruit eating birds in the world...
of South America, a relative of nightjars, lives in caves and uses echolocation
Echolocation
Echolocation may refer to:* Acoustic location, the general use of sound to locate objects* Animal echolocation, non-human animals emitting sound waves and listening to the echo in order to locate objects or navigate...
to catch insects flying in pitch darkness.
Opportunistic feeding
Many other birds are known to engage in hawking as an opportunistic feeding technique or a supplemental source of nutrition: among these are the Cedar WaxwingCedar Waxwing
The Cedar Waxwing is a member of the family Bombycillidae or waxwing family of passerine birds. It breeds in open wooded areas in North America, principally southern Canada and the northern United States.-Description:...
, which mostly eats fruit but is also often observed hawking insects over streams; terns of the genus Chlidonias, such as the Black Tern
Black Tern
The Black Tern, Chlidonias niger, is a small tern generally found in or near inland water in Europe and North America. As its name suggests, it has predominantly dark plumage.- Description :...
, fly in search of insects, sometimes chasing after dragonflies in flight; and even large owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
s that normally feed on rodents will snatch flying insects when the opportunity arises.
Physical Adaptations
Hawking insects, like any feeding strategy, must provide a bird with sufficient nourishment to make the expenditure of energy worthwhile. The strategies and tactics for feeding on airborne insects are inextricably related to the adaptations and lifestyles of the birds that employ them.Flight
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
, especially flight driven by the muscle-powered flapping of wings, is a strenuous physical activity. Although a sally from a perch may look like a single, rapid movement to the human eye, actually the bird must perform several moves: it begins its take-off by pushing with its feet to get into the air, it flaps its wings to generate forward motion (thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
), pursues the prey item, turns in the air, flies back, and, with a final flurry of wings, lands on its perch. When a bird hawks insects, the prey must be substantial enough to pay off in terms of a biological energy budget
Energy budget
An energy budget is a balance sheet of energy income against expenditure. It is studied in the field of Energetics which deals with the study of energy transfer and transformation from one form to another. Calorie is the basic unit of measurement...
. In other words, the bird must take in more energy in food than it is using up in the pursuit of food. Therefore, flycatchers tend to prefer insect prey of moderate size, such as flies, over smaller insects like gnats.
For birds that live in a forest habitat or other setting where short bursts of flight are used in sallies or for getting from tree branch to tree branch, their short, rounded wings are suitable for the rapid flapping required to maneuver in tight spaces. Birds in more open settings that sally after larger insects like bees, such as kingbird
Kingbird
The genus Tyrannus is a group of large insect-eating birds in the Tyrant flycatcher family Tyrannidae. The majority are named as Kingbirds.They prefer semi-open or open areas. These birds wait on an exposed perch and then catch insects in flight...
s and bee-eaters, benefit from longer, more pointed wings, which are more efficient because they generate more lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
and less drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
. Swallows and swifts, which glide about in totally open spaces, have even longer wings. Another function of long, pointed wings is to enable these birds to turn quickly and smoothly in mid-glide. The wingtips create little vortices of air, within which the low air pressure creates additional lift on the wingtips. Furthermore, long, forked tails provide additional lift, stability, and steering ability, which is important for flying at slower speeds (swifts, though capable of flying very fast, actually must fly relatively slowly to intercept airborne insects). In fact, swifts have bodies so well adapted for flying that they are unable to perch on branches or land on the ground, and so they nest and roost on precipices such as rocky cliffs, behind waterfalls (as the Black Swift
Black Swift
The American Black Swift or more simply Black Swift is found from northern British Columbia in Canada through the United States and Mexico to Costa Rica. It is also found on islands in the West Indies....
of North America and the Great Dusky Swift
Great Dusky Swift
The Great Dusky Swift is a species of swift in the Apodidae family.It is found in Argentina, Bolivia, Brazil, and Paraguay. Its natural habitats are temperate forests, subtropical or tropical moist lowland forests, and heavily degraded former forest.-References:* BirdLife International 2004. . ...
of South America are known to do) or in chimneys, as in the case of the Chimney Swift
Chimney Swift
The Chimney Swift is a small bird .-Physical description:In flight, this bird looks like a flying cigar with long slender curved wings. The plumage is a sooty grey-brown; the throat, breast, underwings and rump are paler. They have short tails.-Reproduction:The breeding season of Chimney Swifts is...
.
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
size and shape is also important. Compared to the bills of birds specialized for gleaning, a relatively larger, broader bill is ideal for catching sizeable insects such as bees and flies. The presence of bristles near the bill (rictal bristles) in some flycatchers may be an adaptation for hawking insects; scientists are not sure of the function but they may help protect the eyes or they might actually help provide the bird sensory information as to the location of the prey. Swallows, swifts, and nightjars do not have large bills, but they have wide-gaping mouths. Some nightjars also have bristles around the bill (the Common Poorwill does, the Common Nighthawk does not).
When different kinds of birds have the same adaptations, such similarities are not necessaily indicative of any familial relationship between bird species. Rather, they are the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
. Consider, for example, the marked resemblance in body size, shape, and coloration between flycatchers of several families, though these species are not closely related: the Asian Brown Flycatcher
Asian Brown Flycatcher
The Asian Brown Flycatcher, Muscicapa dauurica, is a small passerine bird in the flycatcher family Muscicapidae. It includes the Brown-streaked Flycatcher, which is sometimes considered a distinct species Muscicapa williamsoni....
(of the Muscicapidae or Old World flycatcher
Old World flycatcher
The Old World flycatcher family Muscicapidae is a large family of small passerine birds mostly restricted to the Old World. These are mainly small arboreal insectivores, many of which, as the name implies, take their prey on the wing.-Characteristics:...
family), Acadian Flycatcher
Acadian Flycatcher
The Acadian Flycatcher is a small insect-eating bird of the tyrant flycatcher family.- Description :Adults have olive upperparts, darker on the wings and tail, with whitish underparts; they have a white eye ring, white wing bars and a wide bill. The breast is washed with olive. The upper part of...
(of the Tyrranidae or Tyrant flycatcher
Tyrant flycatcher
The tyrant flycatchers are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds on Earth, with more than 400 species. They are the most diverse avian family in every country in the Americas, except for the United States and...
family) of the New World, and Slaty Monarch
Slaty Monarch
The Slaty Monarch is a species of bird in the Monarchidae family.It is endemic to Fiji.Its natural habitat is subtropical or tropical moist lowland forests.-References:...
(of the Monarchidae or Monarch flycatcher family), endemic to Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
. All three use flycatching to acquire some or all of their food. But these three families belong to separate branches of the evolutionary tree of songbird
Songbird
A songbird is a bird belonging to the suborder Passeri of the perching birds . Another name that is sometimes seen as scientific or vernacular name is Oscines, from Latin oscen, "a songbird"...
s, which diverged in two branching events some 60 and 90 million years ago and continued to evolve independently in different parts of the world.
Likewise, the similarities of swifts and swallows once lead naturalists to conclude they were related, but it is now established that they are unrelated, and that the same lifestyle has led to the same adaptations.
Ecological Implications
In temperate climates, the availability of flying insects as a food source is seasonal, and this is probably why many birds that rely on this food source during the breeding season migrateBird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
in winter. Migration is timed to the availability of the birds' preferred food. For instance, it has been observed in Great Britain that migrating swallows arrive earlier in the spring than swifts, this correlates with the later profusion of small insects that swifts feed on. Weather also has an impact on the availability of flying insects. Swallows, for example, are obliged to go where the insects are, and depending on the weather they may adjust their choice of prey or be forced to seek out prey in different locations.
The preference for certain kinds of aerial insect as a food source seems to correlate with gregarious or colonial
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in close proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony...
behavior versus territoriality
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
. For birds that take advantage of swarming insects, which are by nature found in local concentrations, colonial breeding can be a successful strategy. An example is the Cliff Swallow
Cliff Swallow
The Cliff Swallow is a member of the passerine bird family Hirundinidae — the swallows and martins.It breeds in North America, and is migratory, wintering in western South America from Venezuela southwards to northeast Argentina...
of western North America. Its relative the Barn Swallow
Barn Swallow
The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...
hunts larger, non-swarming insects, and is more solitary.
Certain neotropical tyrant flycatchers will join mixed-species foraging flocks, as will some Asian drongo
Drongo
The drongos are a family of small passerine birds of the Old World tropics, the Dicruridae. This family was sometimes much enlarged to include a number of largely Australasian groups, such as the Australasian fantails, monarchs and paradise flycatchers...
s. Such flocks stir up flying insects, which can then be picked off in quick sallies.