The Swallow is one of the best known birds and of which more studies have been carried out. These birds have been essential in revealing features about migration, sexual choice, and reproduction itself. It flies in huge flocks and its appearance is estimated as an announcement of the arrival of spring. By continuing this reading you will learn much more about this bird.
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La Golondrina
The swallow that we commonly know is a variety of bird of the passerine order of the Hirundinidae family of migratory customs, which is distributed throughout almost the entire world. It is available in Europe, Asia, Africa, America and Australasia regions. Six subspecies of barn swallow (Hirundo rustica) are known, which proliferate throughout the northern hemisphere, of which four have great migratory performance and their wintering sites include much of the southern hemisphere, reaching central Argentina, South Africa and the northern Australia.
Its extensive range and huge population mean that the species is not at risk of extinction, although local population declines may occur due to particular threats. This bird is an open country bird that regularly makes use of raised structures by humans to reproduce and, as a result, has spread along with human growth. Makes cup-shaped nests from mud balls in barns and similar buildings, and eats insects caught in flight.
Its completely insectivorous diet favors human tolerance towards this species; In times past this acceptance was reinforced by superstitions surrounding the bird and its nest. There are frequent cultural allusions to this bird in literary texts due to its proximity to humans as well as its annual migration. They usually fly in sets.
Description
It is a bird of modest dimensions, where the adult male of the representative subspecies reaches 14,6 to 19,9 centimeters in length, including the 2 to 7 centimeters of the long outer tail feathers. It has a wingspan of 32 to 34,5 centimeters and its weight is 16 to 22 grams.
His back is metallic blue and his forehead, chin and throat are reddish. A thick dark blue band divides the throat from the whitish chest and belly. The outer tail feathers are elongated, giving it the distinctive intensely forked appearance of swallows.
Swallows have two foveas in each eye, giving them sharp lateral and frontal vision to help chase down prey. They also have more or less long eyes, with an extension almost equal to their width. Long eyes allow for increased visual acuity without competing with the brain for space within the skull. The morphology of the eye in swallows is similar to that of a bird of prey.
It shows a series of white spots along the outer end of the upper part of the tail. The appearance of the female is similar to that of the male, but the tail feathers are shorter, the blue of her back and of the chest stripe is less lustrous and the chest and bellies are paler. When young it is browner and shows a paler reddish face and whiter underparts; does not have the extensive tail feathers of adults.
The unique mix of reddish face and blue pectoral stripe further differentiates the adult Barn Swallow from the African varieties of Hirundo and the Australian Swallow (Hirundo neoxena), whose ranges overlap in Australasia. In Africa, the tail the shorter length of the young can be confused with the young of the red-breasted swallow (Hirundo lucida), although the latter shows a narrower pectoral stripe and whiter on the tail.
The song of the barn swallow is a warble that frequently ends in a su-seer in which the second note is higher than the initial although its pitch is declining. When excited their intonations incorporate a witt or a witt-witt or a loud splee-plink or when trying to scare off predators from the vicinity of the nest. Warning signals incorporate a sharp siflitt when predators such as cats appear and a flitt-flitt when birds of prey manifest. This variety is extremely quiet in its winter roosts.
The shedding of flight feathers occurs in winter shelters, which makes subspecific recognition of individuals difficult in that season. The postbreeding change is very gradual and in Europe it begins in August prior to migration with the change of body plumage and sometimes with that of the feathers that cover the middle area of the wings. In India, this change will occur gradually and irregularly, lasting through most of the winter and not yet ending in April in certain individuals.
In contrast to swifts (Apus apus), swallows can perch horizontally, since the length of their legs gives them adequate support to take flight again from the ground.
Taxonomy
It was Carlos Linnaeus in 1758 who reviewed the barn swallow as a species in the tenth edition of his work Systema naturae with the scientific name of Hirundo rustica. Hirundo means "swallow" in Latin; rusticus translates as “country”. It is the only one of the varieties of the genus Hirundo that has spread to the Americas, most of them being native to Africa.
There are few taxonomic problems in this genus, although previously the red-breasted swallow (Hirundo lucida), a sedentary variety from western Africa, the Congo basin and Ethiopia, was considered a subspecies of barn swallow. The red-breasted variety is slightly smaller than its migrating relative, shows a narrower blue pectoral band, and smaller tail feathers in adults. In flight it shows a paler coloration on its underparts.
Evolution
Behavioral variations can initiate morphological evolution by driving lineages to novel adaptive zones. This has been evaluated primarily in ecological behaviors, such as obtaining food, but social behaviors can also modify the morphology. Swallows and house martins (Hirundinidae) are flying insectivores that display a variety of social behaviors, from solitary breeding to colonization and feeding.
Using a well-deciphered phylogenetic tree, a database of social behaviors, and morphological measurements, we question how modifications from solo reproduction to social reproduction and foraging (foraging) have impacted morphological development in Hirundinidae. Using a discrete-state developmental threshold pattern, we find that changes in both reproductive and foraging social behavior are frequent throughout the phylogeny of the swallow.
Lonely swallows have a highly variable morphology, while social swallows have much less general variation in all of their morphological traits. Confluence measurements based on both the path of social lineages through morphospace and the general morphological distance between social varieties, scaled by their phylogenetic separation, point to strong concurrence in social swallows, particularly socially foraging swallows.
The more modest physical attributes usually seen in social species mean that social varieties take advantage of a differentiated flight style, possibly increasing maneuverability and foraging success and lessening mid-air collisions within large flocks. Such results highlight the relevance of sociality in the evolution of species, a link that had previously been evaluated only in eusocial insects and primates.
Subspecies
There are a number of six widely recognized Barn Swallow subspecies. Complementary or alternative subspecies have been raised for East Asia, including saturata (Robert Ridgway, 1883), kamtschatica (Benedykt Dybowski, 1883), mandschurica (Wilhelm Meise, 1934), and ambigua (Erwin Stresemann, 1940). Since these forms are of doubtful validity, in this article we continue the classification of Turner and Rose (1989):
H.r. Rustic.
The nominate subspecies is found from Europe, Asia Minor, and Iraq eastward to the Yenisei River basin, the western Altai Mountains, Xinjiang, China, and Sikkim, India, as far north as the Arctic region and south to North Africa. It makes its migration to Africa, Arabia and areas of the Indian subcontinent, such as Sindh, Punjab and Sri Lanka. Barn swallows wintering in southern Africa arrive from much of Eurasia, from the 91st meridian east. About 80% of the swallows that migrate to southern Africa come from Russia.
This subspecies is recognized by displaying an entire pectoral stripe. Occasional individuals occur throughout the reproductive range of H. r. rustica whose pectoral band is relatively faded with reddish, but these birds are few and its pectoral band is not as faded as in the gutturalis, which would favor the recognition of both subspecies in winter shelters.
Its underpart becomes whiter as the feathers wear down, but certain individuals may have it white even with their recently changed plumage. Other feasible shades are pinkish, pale pinkish, cream, off-white and dirty white. The metallic brilliance of its upper area is purplish blue. It is larger than the gutturalis.
H.r. transitive
It was reviewed by Ernst Hartert in 1910 and is found in the Middle East, from southern Turkey to Israel, and is more or less sedentary, although some specimens winter in East Africa. They exhibit orange-red underparts and a split pectoral stripe.
H.r. savignii
The subspecies, native to Egypt, was reviewed by James Francis Stephens in 1817 and named after the French zoologist Marie Jules César Lelorgne de Savigny. It is similar to transitive, also showing orange-red underparts, but savignii exhibits a complete pectoral band and a more intense reddish hue in its lower areas.
H.r. gutturalis
This variety was reviewed by Giovanni Antonio Scopoli in 1786, and exhibits characteristically oxidized ocher undersides, but the color is variable throughout (not even as in tytleri). It exhibits a split in the pectoral stripe and the brilliance metallica of its upper areas is blue-green. It is found in eastern Asia, east of tytleri and the nominate subspecies. From Yakutsk to the Sea of Okhotsk littoral and in Kamchatka there is a gradual replacement between this subspecies and tytleri, favoring one or the other depending on which direction it is pointed. It mixes with tytleri in the Amur River area.
The two East Asian subspecies were thought to have once been geographically divided, but nesting sites brought about by human growth made it possible for their ranges to overlap. Its primary breeding range is Japan and Korea. Populations that occur in the central and eastern Himalayas, where it is found only in widely separated colonies, have been incorporated into gutturalis, although there has been disagreement about their identity and they were listed by Stresemann (1940) as a subspecies. separate: ambiguous.
The subspecies gutturalis appears to have a greater presence in Southeast Asia than tytleri and is found further south. It also migrates to the Philippines, India (primarily east and south), and Sri Lanka. H. r. gutturalis is an occasional marauder in Alaska and Washington, but is easily distinguished from the American subspecies, H. r. erythrogaster, due to the reddish color of the lower areas of the latter.
H.r. Tytleri
Reviewed by Thomas C. Jerdon in 1864 and named after English soldier, naturalist, and photographer Robert Christopher Tytler. It shows evenly chestnut underparts areas and an incomplete pectoral band. The tail is more extensive. It is found in southern Siberia from the Angara River basin east to Yakutsk and the Oliokma River and south to northern Mongolia.
It winters in Southeast Asia, as far south as western Malaysia, and in the eastern part of the Indian subcontinent. Apparently it is not so common in Mediterranean China, a nation in which it has been seen primarily migrating to the northeast and along the coast.
H.r. erythrogaster
The American subspecies was noted by Pieter Boddaert in 1783. It differs from the European subspecies in that its undersides are redder and its blue pectoral stripe is narrower, often incomplete. It is found throughout North America, from Alaska to southern Mexico, and migrates to the Lesser Antilles, Costa Rica, Panama, and South America for wintering.
Some spend the winter in the southernmost parts of their breeding range. The migratory route of this subspecies is reduced in Central America, so it is abundantly found during such a journey in the lowlands of both coasts.
According to the author that follows, saturata has been considered equivalent to erythrogaster, gutturalis or tytleri. On the other hand, kamtschatica and mandschurica have been associated with erythrogaster, saturata, itself without great universal recognition, and gutturalis. Finally, ambigua has been considered as equivalent to the nominate subspecies and gutturalis, with the second option considered the most accepted.
Behavior
It is a diurnal species and migratory in nature. They are often seen in huge groups perched on telephone wires or other tall structures. They nest in colonies, possibly because of the spread of high-quality nesting sites. They use vocalizations as well as body language (positions and movements) for effective communication. They sing alone and in chorus.
They show a wide variety of calls used in different situations: alarm signals when predators appear, calls for courtship and for chicks in the nest. The chicks broadcast a weak trill when asking for food. Barn Swallows also generate clicking sounds by rapidly closing their jaws.
At a sizable roost in Cross River, Nigeria, swallows began clicking their bills and twittering at twenty minutes before dawn. In the next few minutes, his vocalizations grew in intensity. Numerous specimens began to fix their plumage, to lengthen their wings and to flap their wings. The first swallows to come out regularly did so between zero and nine minutes before dawn (on rare occasions, between one and three minutes after sunrise), to be followed by their congeners en masse about five minutes later.
The exit of all the swallows from the roost took from twenty to forty-nine minutes, however, 90% of them left it in less than ten minutes. Most of the swallows took flight upwards, with great speed and as vertical as possible, delineating sometimes sharp spirals to gain altitude. The flocks spread out when they had already moved away from the roost.
In the afternoon, the birds gyrated in compact masses until sunset, at high elevations due to the presence of African falcons (Falco cuvierii), and then accelerated their massive and abrupt descent into a variety of reverse tornado. Most tried to secure a position as high as possible on the hill where the roost was located.
Formerly it was considered that swallows could hibernate in a state of torpor, including sheltering for the winter under water. Aristotle imputed hibernation not only to swallows, but also to storks and kites. The hibernation of swallows was considered possible even by an observer as keen as the Reverend Gilbert White, in his text The Natural History and Antiquities of Selborne (1789, based on decades of observations).
This notion may have been based on the habit of certain species to doze off in some numbers in lofts, nests, and other kinds of shelter during bad weather, and some varieties even go into torpor.
Several reports of presumed torpor in swallows have been known since 1947, such as a 1970 report that the white-backed swallow (Cheramoeca leucosterna) in Australia can conserve energy in this way, but the initial corroborated study that they or any passerines do enter in torpor was a 1988 analysis of swallows of the genus Delichon.
Food
It generally has habits very similar to other aerial insectivores, including other varieties of swallows and the phylogenetically unrelated swifts. It is not a very fast bird, with a calculated speed of about eleven meters per second that can reach twenty, and a flap of wings about five and even seven or nine times per second, but its maneuverability is sufficient to capture insects. in flight. It is frequently seen flying at more or less low altitudes in open or semi-open areas.
The swallow usually takes its food seven or eight meters above shallow water or the ground, often escorting animals, humans, or farm machinery to catch the frightened insects, but sometimes it catches its prey from the very surface of the water, walls or plants. Diptera (flies and mosquitoes, and so on), Orthoptera (grasshoppers and crickets), Anisoptera (dragonflies), Coleoptera (beetles), Heterocera (moths), and other flying insects make up 99% of their diet.
In its reproductive distribution zone, the enormous Diptera make up about 70% of its diet, where aphids are a very significant component. However, in Europe, barn swallows eat fewer aphids than house martins (Delichon urbicum) and sand martins (Riparia riparia). In their winter roosts, Hymenoptera, particularly flying ants, are an important food source.
Throughout the egg-laying period, swallows hunt in pairs, but in other situations they frequently form huge flocks. The baby swallow moves skimming the water of lakes or rivers in flight, while bathing by splashing in the water for a few seconds while it flies. It is also capable of feeding its chicks as it flies. A study in West Virginia found that barn swallows forage within 1,2 kilometers of their nests.
In Europe, they forage only about 500 meters from their nests. After the breeding season, they congregate in communal roosts. The reedbeds are usually a place of predilection for the choice of swallows, which turn en masse before rushing over the reeds. Reedbeds are an important source of food before and during migration.
Although the Barn Swallow migrates by day and can feed by flying while moving at low altitudes over the ground or water, the reedbeds allow them to dispose of or replenish their fat reserves. Swallows exhibit a weight gain of 2 to 4 grams prior to migrating north to their breeding range, often at the end of the molt cycle.
Reproduction of the Swallow
The reproductive period of barn swallows usually extends from May to August, but this varies a lot according to the place. It has reproductive capacity already in the first reproductive stage after birth. In general, young swallows do not lay as many eggs as they do in adulthood.
These birds harass prying eyes such as cats and birds of the genus Accipiter that dare to approach their nests, by flying very close to these predators. Nest parasitism, in which brown-headed cowbirds (Molothrus ater) in North America and of the cuckoos in Eurasia, they lay their eggs in the nest of the swallow, it is rare. At least for the brown-headed cowbird, cases have been reported in which the parasitic chick was successfully reared and was able to leave the nest, evidencing that the barn swallow is an appropriate host for this species.
There are also records of the hybridization of the barn swallow with the barn swallow (Petrochelidon pyrrhonota) and the cave swallow (Petrochelidon fulva) in North America, and with the house martin (Delichon urbicum) in Eurasia. From this further crossing one of the most frequent passerine hybrids was produced.
Pairing
Males return to breeding grounds before females and choose a nest site, which is shared with females by circling and humming. They also try to attract them by extending their tails. Females have a particular predilection for males with proportionate wings and tails. Males showing a higher level of symmetry obtain a mate much more quickly than asymmetric ones.
The lack of proportionality may be due to genetic causes such as inbreeding and mutations or to environmental causes such as insufficient food, the spread of parasites or the appearance of pathogens. Individuals impacted by these factors not only show a higher level of asymmetry but also lower strength and longevity. Therefore, females that choose symmetrical males would be choosing superior males.
The reproductive success of males is also linked to the length of their tail, with the longest tails being the most attractive to females. The males with the most extensive tail feathers are usually longer-lived and more resistant to diseases, for this reason they are selected by the females, obtaining an indirect reproductive advantage with said choice, since prolonged tail feathers indicate genetic supremacy of a male. individual that will generate an offspring of greater vitality.
Males with long tails also have larger white spots on their tails, and since avian lice favor white feathers, the appearance of these spots without parasite damage is a sign of an individual's reproductive status. . There is a positive association between the size of these spots and the number of offspring sired per season.
Northern European males have longer tails than those from the south; while in Spain the tails of males are barely 5% longer than those of females, in Finland the disparity is 20%. In Denmark, mean male tail length increased by 9% between 1984 and 2004, but further climatic modifications are likely to lead to the development of shorter tail lengths as summers become hotter and drier. . There is also evidence that males usually choose mates with long tails.
Individuals of both sexes guard the nest, but the males are peculiarly violent and territorial. Pairs that have successfully reproduced may last for several years. On the other hand, mating outside the pair is frequent, therefore, this variety is genetically polygamous, although it manifests itself socially as monogamous. The males take care of the females continuously to prevent being "deceived" and can use false alarm calls to hinder copulation attempts of their pair with other males.
Males that do not have a mate frequently associate with a partner for even the entire breeding season. Although these "collaborators" do not usually feed the chicks, they can collaborate in the construction and protection of the nest, incubation of the eggs and rearing of the young. Collaborators are preferably male.
Nest Construction
The Barn Swallow regularly makes its nest inside easily accessible buildings such as barns and stables and under bridges and piers. Before there was a profusion of structures erected by humans, swallows made their nests on cliffs or in caves, but this is not so common today.
The meticulous pot-shaped nest is placed on a beam or against some suitable vertical element. It is built by both members of the pair, although more frequently by the female, by collecting the small balls of clay in their beaks and covering them with grass, feathers, freshwater and marine algae, and other soft components. Swallows may build their nests in colonies in which there are sufficient high-quality nest sites and, within the colony, each pair remains in defense of territory that it possesses. surrounds the nest, which, in Europe, is 4 to 8 square meters.
In North America it is known that swallows frequently engage in a mutualistic association with ospreys (Pandion haliaetus). Swallows make their nests under those of ospreys, in this way they receive protection against other birds of prey that are scared away because this eagle bases its diet exclusively on fish. Similarly, the alert calls of the swallows warn the ospreys of the appearance of these predators.
Brood and Rearing of Chicks
The females lay from two to seven eggs, usually four or five, whitish with reddish spots. The eggs have a size of 20 by 14 millimeters and their weight is 1,9 grams, of which 5% concern the shell. In Europe, the female is responsible for most of the incubation, but in North America the male can do it in a quarter of the time. The incubation period is usually 14 to 19 days, with another 18 to 23 days added before the immature chicks leave the nest.
The young that can already fly, stay with their parents and are fed by them for about a week more. In the second week after leaving the nest, the chicks have already spread and often move to other colonies of swallows. The two parents provide food and protection for the young and remove the fecal sacs from the nest, although it is the females who provide greater parental care. The parents usually feed the chicks in the nest up to 400 times a day.
The swallows feed their small insects, which they compress into a ball, which is carried to the nest in the throat of the adult. On occasions, the chicks of the initial brood collaborate in feeding those of the second. They regularly have two clutches per season. The nest in which the first was raised is reused for the second and tidied up and used again in subsequent years. The survival of nests for 10 or 15 years is in line with proper maintenance and one was known to have been used for 48 years.
The percentage of chicks that hatch is 90%. The average mortality is 70 to 80% in the initial year and 40 to 70% for adults. Although the record age exceeds 11 years, most do not exceed four. Chicks count with red and bulging mouths, a characteristic that, according to what has been shown, encourages parents to feed it. The depth of color in their mouths is linked to their immunocompetence, and chicks from large clutches have less conspicuous mouths.
Habitat and Distribution Area
The favorite habitat of the swallow is a field without major obstacles in height, with low elevation vegetation, such as pastures, meadows and agricultural orchards, predominantly with water in the vicinity. This bird avoids areas of thick vegetation, steep or large urban developments.
The existence of open and easily accessible structures such as barns, stables and small bridges that offer places to build nests and exposed locations such as wires, roof edges and bare branches to perch, are also of importance in the choice that this bird makes. their breeding sites.
In its migration, it usually flies over open areas, often near water or around mountain ranges. It is found in the Holarctic region, from sea level to usually 2700 meters, but up to 3000 meters in the Caucasus and North America, and is only unavailable in the deserts and northernmost cold areas of the United States. continents. Breeding ranges include North America, northern Europe, north-central Asia, northern Africa, the Middle East, southern China, and Japan.
It migrates to South America, South Asia, Indonesia, and Micronesia. Birds that breed in East Asia winter throughout tropical Asia, from India and Sri Lanka to Indonesia and New Guinea. They migrate to northern Australia in increasing numbers. In large areas of its range, it avoids cities and in Europe it is replaced in urban areas by the common house martin (Delichon urbicum). However, in Honshū, the Barn Swallow is a decidedly urban bird, being replaced by the Golden Swallow (Cecropis daurica) in rural areas.
The reproduction of the Barn Swallow has been verified in the more temperate zones of its winter distribution area, such as the mountains of Thailand and central Argentina. Specimens usually return to spend the winter at the same site each year. In winter, the Barn Swallow is universal in its choice of habitats, avoiding only thick forests and deserts.
It is most prevalent in open, low-vegetated habitats such as plains and ranches, and in Venezuela, South Africa, and Trinidad and Tobago it was reported as specifically prone to burned or already harvested sugarcane fields.
In warm and southern Africa, this variety is very gregarious and gathers in roosts of up to a few million individuals in reedbeds, fields of sugarcane, corn, elephant grass (Pennisetum spp.) or plant structures of a similar structure. For example, the modest reed bed of Mount Moreland, near Durban in eastern South Africa, brings in more than three million individuals each night, more than 8% of those that breed in Europe.
Likewise, there are only a few hundred individuals. Regularly, the roosts are located in very clear habitats, where there are no impediments that hinder the ascents and descents of the swallows. In the absence of suitable roosts, they sometimes rest on wires where they are more exposed to predators. On December 23, 1912, the initial case of a barn swallow that had made its migration from the United Kingdom to South Africa was recorded; a ring was placed on the specimen in Staffordshire and it was rescued in Natal.
Isotope studies have shown that throughout the winter the different populations eat in different habitats: the birds found in the United Kingdom feed mostly on fields, while the Swiss specimens use mostly forests. Another isotopic analysis produced the result that the same population from Denmark wintered in two different areas. As expected of a long-distance migrant, this bird has been reported as a prowler as far afield as Hawaii, Bermuda, Greenland, Tristan da Cunha, and the Falklands.
Predators and Parasites
Barn Swallows (and other modest-sized passerines) frequently show characteristic dimples in their wing and tail feathers. Such holes were once thought to be caused by avian lice such as Machaerilaemus malleus and Myrsidea rustica. However, other studies indicate that they could be caused by ischnocera of the genus Brueelia.
Varieties of lice for which the barn swallow is a host include Brueelia domestica and Philopterus microsomaticus. In Texas, Oeciacus vicarius, which frequently infects Rock Martin (Petrochelidon pyrrhonota), has also been found in Barn Swallows.
Communal roosts are attractive to predators: numerous species of falcons and accipitrids take advantage of these opportunities. They stand out among their predators:
- Humans, the variety that causes the greatest number of casualties to the Barn Swallow,
- Chikra Sparrowhawk (Accipiter badius),
- Cooper's hawk (Accipiter cooperii),
- Little Sparrowhawk (Accipiter minullus),
- Small Esparvero (Accipiter striatus),
- Toussenel's goshawk (Accipiter toussenelii),
- Marsh Harrier (Circus aeruginosus),
- Amur Kestrel (Falco amurensis),
- Slaty Kestrel (Falco ardosiaceus),
- Borni Falcon (Falco biarmicus),
- Red-necked Falcon (Falco chicquera),
- African Hawk (Falco cuvierii),
- Peregrine Falcon (Falco peregrinus),
- American Kestrel (Falco sparverius),
- Eurasian Falcon (Falco subbuteo),
- Gabar Sparrowhawk (Micronisus gabar),
- Black Kite (Milvus migrans ssp. parasitus),
- Caricalvo's Harrier (Polyboroides typus ssp. pectoralis),
- Eastern Owl (Megascops asio),
- European Scops Owl (Otus scops),
- African Tawny Owl (Strix woodfordii),
- Barn Owl (Tyto alba),
- Senegalese Cuckoo (Centropus senegalensis),
- Gulls (Laridae),
- Boattail Grackle (Quiscalus major),
- Northern Grackle (Quiscalus quiscula),
- Domestic Cat (Felis silvestris),
- Bobcat (Lynx rufus),
- Weasels (Mustela spp.),
- Raccoon (Procyon lotor),
- Brown Rat (Rattus norvegicus),
- Squirrels (Sciuridae),
- snakes etc
Predatory bats such as the greater vampire bat (Megaderma lyra) are known to feed on barn swallows. Most predators attack chicks, while sparrowhawks, hawks, and owls go after adults. Swallows elude predators with their dynamic flight and build their nests in places that are difficult for them to access.
The departure and return of swallows from and to their roosts are highly synchronized and predictable. More than 90% of the birds in a roost of 1,5 million beings in Nigeria left and returned within ten minutes around corresponding sunrise and sunset, in compact, fast-moving masses.
The African falcons matched their arrival with the dynamics of the swallows, the first arriving from 2 to 14 minutes before the departure or return of the initial individual, and leaving whenever most of the swallows had left. At twilight, the first ones arrived at the roost 15 to 20 minutes before sunset, when regularly the swallows were still absent.
Swallows sought to reduce the risk of predation by gathering in large numbers, restricting their departure and return to a short time, and making rapid, synchronized ascents and descents to avoid predators. As the swallows returned at dusk, they responded to the appearance of hawks. gaining lift in the air and squeezing into thick masses, so the hawks would then have to fly higher than at dawn to approach them.
Hunting by these predators in the early morning was very different, since the swallows would have to ascend from ground level and would react to the appearance of hawks with a low flight, leaving the roost at high speed and without moving away from the birds. nearby elephant grass until they reached the edge of wooded areas. These flocks were attacked by means of harassment in brief and repeated dives, which caused the swallows to spread in all directions.
When the swallows left the roost in a vertical climb, the falcons attacked them, rushing at them from the top, turning upwards after each bite. Being aerial hunters, the falcons could only attack the swallows effectively when they were present in the roost and in the air, that is, in the short period of 30 minutes around sunset and sunrise. However, they seemed to largely avoid ramming large crowds, which might be difficult for them to tackle.
They were generally unaware of the huge numbers that massed out rapidly and upward at dawn and those that gathered at high altitude at twilight and then plummeted down to the roost, concentrating on stragglers and modest early or late aggregations. .
Although they hunted isolated subjects and groups of between two and 15.000 individuals, they were more successful when they hunted groups of less than 50 individuals. The predation danger to swallows taken individually decreased dramatically with flock size.
State of conservation
The Barn Swallow comes nowhere near the range and population size considerations for vulnerable species on the IUCN Red List: it has a huge range spanning some 43,4 million square kilometres. and it is estimated that its planetary population exceeds 190 million individuals.
Although the population propensity appears to be negative, it is estimated that this reduction in numbers is not fast enough for the species to approach the criteria of the referred list (that is, a drop in its populations of more than 30 % in a decade or three generations). For these reasons, the barn swallow was listed as "least concern" on the 2012 Red List, and has no special status under the Convention on International Trade in Endangered Species. of Wild Fauna and Flora.
Historically, this variety has taken advantage of the clearing of forests, which make up the cleared habitats that are prone to it, and the presence of humans, which provides them with abundant reliable nesting sites. Local decreases have occurred due to the use of DDT in Israel in the 1950s, motivated by competition for nesting sites with the house sparrow (Passer domesticus) in the United States in the XNUMXth century and by the massification of agriculture, which reduced the existence of insects, in areas of Europe and Asia today.
However, an increase in North America through the 2006th century has been recognized due to the greater existence of nesting sites and the consequent expansion in its distribution area, which includes the colonization of northern Alberta. In XNUMX, it was claimed that the populations of this bird in the United Kingdom had decreased, perhaps due to drought and the use of pesticides on its migration route and the transformation of rural buildings and other nesting sites. favorites in the UK itself.
On the other hand, according to the information made public in 2007 and 2008 respectively, this bird would have suffered a modest or statistically negligible population decrease in the previous four decades in North America and would have remained stable in Europe since 1980.
Change in climate can impact barn swallows. Swallows in Africa and throughout their migration show huge variations in their body mass and fat reserves according to the atmospheric conditions in which they find themselves. Drought causes weight loss and gradual renewal of feathers, and the enlargement of the Sahara will make this desert an even greater impediment to European birds.
In a dry season, the swallows that wintered in Botswana presented low weight and zero fat, while in years of heavy rains and, therefore, a high number of insects, they reached a higher weight and greater fat reserves. Similarly, in Nigeria for February 2001, the gust of Harmattan winds was consistent with a marked drop in body mass and a lack of fat in swallows, where higher weights were recorded both before and after that wind faded. dry.
Similarly, warm and dry summers reduce the existence of insects with which to feed the chicks. Conversely, warmer springs could extend their breeding season and help generate more chicks. In 2014, the Barn Swallow was named Bird of the Year by SEO/BirdLife, the scientific organization dedicated to studying and preservation of birds in Spain since 1954.
According to SEO/BirdLife, its population monitoring records throughout the region indicate that the swallow has suffered a loss of 30% of its population in Spain in the recent decade, due to, among other reasons, the use of pesticides in the countryside, the abandonment of agriculture, the devastation of traditional constructions and the new forms of architecture.
Relationship with the Human Being and Cultural References
Swallows are tolerated by humans because of their beneficial role as insect eaters, and certain varieties have readily adapted to nest in and around human settlements. Today, the Barn Swallow and the House Swallow rarely use natural sites.
The purple swallow (Progne subis) is also actively encouraged by people to nest in the vicinity of humans and elaborate nest boxes are made. Abundant artificial nesting sites have been established that the Purple Swallow now rarely nests in natural openings in the eastern section of its range.
Historical References
The historian of Rome, Pliny the Elder, reviewed the use of painted swallows to notify about the winning horses of a race. Throughout the XNUMXth century, Jean Desbouvrie tried to domesticate swallows and train them for use as messenger birds, as an alternative to war pigeons. He was able to stem the migratory drive of the young birds and convinced the French government to carry out initial tests, but further experimentation was stopped.
Subsequent attempts to train the search behavior of swallows and other passerines experienced difficulty in determining a statistically significant success rate, although birds are known to repeatedly allow themselves to be caught seeking bait from traps.
According to a nautical superstition, swallows are a good omen for those who are in the sea. This is possibly due to the fact that swallows are land birds, so their appearance notifies the sailor that he is close to shore. An ancient term of worshiping swallows is a "flight" or "sweep."
The Swallow in Culture
In ancient times, swallows seem to have used bridges and other buildings erected by humans since ancient times. An early allusion to this bird can be found in Virgil's "Georgics" (29 BC): […] garrula quam tignis nidum suspendat hirundo. ("[...] the twittering swallow suspends its nest from the rafters".)
Swallows are believed to have started sticking their nests to Native American buildings in the early XNUMXth century. It is possible that the consequent expansion of the human being in North America caused a dramatic spread of the species throughout the continent.
There are references to the northern migration of swallows as "image of spring and summary of summer" in the northern hemisphere. The barn swallow represents the arrival of spring and love in "Pervigilium Veneris", a late Latin poem. In "The Waste Land," TS Eliot referred to the line Quando fiam uti chelidon [ut tacere desinam]? ("When will I be like a swallow, so I can stop being silent?").
This alludes to a version of the Philomela myth in which she is transformed into a nightingale and her sister Procne into a swallow; in less frequent versions, the varieties are indicated inverted. Conversely, the depiction of a flock of swallows in flight on their migration south culminates John Keats's ode "To Autumn":
Where are the spring songs? oh! In which place?
Do not meditate on them anymore, because you already have your music,
when dappled clouds make the soft bloom
perish by day and color the stubble pink;
so that the sore chorus of mosquitoes
Between river willows it groans, rising
or descending, according to the blow of the breeze;
and the ripe lambs bleat in the mountains;
the cri-cri of the cricket in the hedge; and already, with a soft trill,
In the fence garden, the robin sings
and gather swallows, chirping, in the firmament.John Keats
In the false Gospel of Pseudo-Thomas, it is related that Jesus, when he was five years old, "was playing one day in a riverbed... he prepared a soft mass of clay and shaped a dozen swallows with it."
Swallows are cited in various works by William Shakespeare for their lightness in flight; for example True hope is swift, and flies with swallow's wings […] (“The authentic hope is swift and in its flight it carries swallow wings […]”) from act five of Richard III. Shakespeare likewise alludes to the annual migration of the swallow in The Winter's Tale, act four: Daffodils, That come before the swallow dares, and take The winds of March with beauty […] that the swallows dare and take the winds of March with beauty[…]”).
The swallows are also represented in one of the most famous Rhymes of Gustavo Adolfo Bécquer.
"The gloomy swallows will return
on your terrace their nests to make,
and again with the wing to its crystals
fiddling they will call.But those that the flight contained
your beauty and my joy to contemplate,
those who learned what we were called...
those... will not return!The thick honeysuckle will return
from your garden the fences to climb,
and again in the evening even more beautiful
its flowers will bloom.But those that condensed from dew
whose drops we watched shiver
and rush like tears of the day…
those... will not return!They will return from the love in your ears
the burning words to sound;
your heart from its intense sleep
maybe he'll wake up.But voiceless and abstracted and on his knees,
as God is venerated before his altar,
as I have adored you..., be disillusioned,
no one like that will love you.”Gustavo Adolfo Becquer
Oscar Wilde co-stars a swallow in his story "The Happy Prince." And the poet Swinburne questions the swallow in his poetry "Itylus", referring to a Theban version of the Greek legend of Aedon or Edon in which Chelidon or Chelidonia is turned into a swallow and Aedon into a nightingale. The poet Eduardo Fraile published his text "Balada de las Golondrinas" (Pre-Textos, 2009) regarding the swallows of his town, Castrodeza.
Fun Facts about the Swallow
Swallows are part of the Hirundinidae family, which also includes airplanes. There are 88 varieties recognized throughout the planet. Swallows are not even remotely related to swifts. The familiar swallow or barn swallow is commonly known as the barn swallow.
It is located throughout the northern hemisphere, which includes all European countries except Iceland. This common species is the most widespread swallow in the world, but other similar species are found in Africa. The Australian Swallow is also closely related.
Gilbert White made a detailed study of the Barn Swallow in his work "The Natural History of Selborne", but even this careful observer was not sure whether swallows migrate or hibernate in winter. Barn Swallows eat vast amounts of insects and are of importance in controlling their populations.
A pair of swallows requires at least 1.200 trips to build their nest. Only females line the nest. These birds like to nest near large farm animals such as cattle or horses. The decline in dairy farming in the UK and the consequent increase in arable crop production has not been very appropriate for the species.
A long tail increases its maneuverability, and it can also function as a sexual adornment, since such a tail is more frequently found in males. Its legs are short in length, and its feet are suited to standing upright rather than walking, as the fore toes are relatively close together at the base. Swallows can walk and even run, but they do so with a dragging, waddling motion.
Swallows have the ability to generate many different sounds or hums, which are used to express emotion, for communication with others of the same species, through courtship, or as a warning when a predator is in the vicinity. The usual song of the swallows is a simple and sometimes musical twitter. A “tswit-tswit” call is expressed when a predator is spotted.
Various European and North American species are long-distance migrants; in contrast, Western and South African swallows do not migrate. Migratory species cover 320 miles (200 kilometers) each day, primarily during the day, as fast as 27 to 35 miles per hour (17 to 22 kilometers per hour). The highest flight speed is 55 km/h (35 mph). Certain species, such as the mangrove swallow, are territorial, while others are not and are restricted to defending them.
Swallows and swifts are completely unrelated, but on the surface they look very similar. The swallow is called the "freedom bird" because it cannot tolerate captivity and will only mate in the natural environment
In ancient times, condescension towards this profitable insectivore was increased by superstitions surrounding the destruction of their nests. It was considered that such an act could cause cows to produce bloody milk or no longer produce it at all or chickens to no longer lay eggs. On the other hand, in Nigeria, hundreds of thousands are caught each year, making it the human being in the main predator of this species by far.
Much folklore exists around the swallow. Observing the first swallow of the year is estimated as a good omen. In Russia songs were written to celebrate his return after the long and cold winter. Before the puzzles of migration were understood, swallows were thought to spend the winter entombed in the mud of reservoirs and lakes. Swallows usually drink in the air, in a low flight to suck up the water.
One of the most requested tattoos to record is the swallow. The tattoo can mean many things, for example, many years ago ancient navigators tattooed swallows to guarantee their journey, particularly if it exceeded 5.000 nautical miles. Said tattoo became a kind of amulet for the beginning, course and return of the trip, in such a way that a sailor tattooed with a swallow had traveled more than 5.000 nautical miles (9.260 kilometers) and one with two tattooed swallows would have traveled 10.000 miles. nautical (18.520 kilometers).
Even the Egyptians believed that the swallows guarded the souls of the deceased, so their admiration for the swallows was enormous. Certain elements were formulated to give a particular meaning to swallow tattoos, namely a swallow singing or flying is a sign of freedom. The swallow is also identified as an emblem of love for life, since they, within their behavior and courtship when uniting with another swallow, do not depart from it ever again.
The swallow warns of the arrival of a new season, the color begins, new lives, a hope, perhaps for this reason people use it to paint them on their bodies. The barn swallow is held in Estonia as the emblem bird of the nation.
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