Bank swallows, or sand martins as they are known in Europe and Asia, are one of the few small passerine birds that have an almost cosmopolitan distribution. They migrate between discrete breeding and wintering ranges. Bank swallow distribution in the breeding range is most limited by suitable nesting habitat. Winter distribution is influenced by appropriate foraging areas. (Garrison, 1999)
In the Americas, bank swallows breed throughout much of Alaska and Canada to the maritime provinces and south to the mid-Atlantic United States, throughout much of the Appalachian chain, along the Ohio River Valley to Missouri, west throughout much of Kansas, along the Rocky Mountain Chain into New Mexico, and in the mountainous regions of Utah, Nevada, and northeastern California. They also breed along the Rio Grande river in Texas and northern Mexico. In winter, American populations migrate to throughout South America and along the western coastal slopes of Mexico. They are rare visitors to some Antillean islands in winter. (Garrison, 1999)
In the Old World, bank swallows (or sand martins) breed throughout northern Eurasia, from the British Isles, across Scandinavia, northern Russia, and Siberia, and as far south as the Mediterranean, Middle East, the Nile River valley, northern, coastal Africa, northwestern Africa, Iran, Afghanistan, India, and Pakistan to as far east as southeastern China and Japan. They winter throughout the Arab Peninsula and Africa, including Madagascar. They can also be found throughout much of southern and southeastern Asia in winter, including the Philippine Islands. (Garrison, 1999)
Their scientific name (Riparia riparia) refers to the preferred breeding habitat of bank swallows. They nest in small to large colonies in soft banks or bluffs along rivers, streams, and coastal areas. They prefer the eroding banks of low-gradient, meandering rivers and streams. They also use sandy coastal bluffs or cliffs. Man-made habitats are now also used, including gravel pits, quarries, and road cuts. They are found from sea level to 2100 meters elevation, but most populations occur in lowland river valleys and coastal areas. Important foraging habitats include wetlands, large bodies of water, grasslands, agricultural areas, and open woodlands. Bank swallows mainly migrate along large bodies of open water, such as marshes, coastal areas, estuaries, and large rivers. In winter they are seen mainly in open habitats with large bodies of water and grasslands, savannas, or agricultural areas. (Garrison, 1999)
Bank swallow populations worldwide vary slightly in plumage color and size, but variation seems to be clinal. Their ability to disperse over very large distances suggests that gene flow can occur at continental levels at least. At one point 8 subspecies were recognized, but currently only 3 subspecies worldwide are recognized: R. r. riparia, a cosmopolitan subspecies, R. r. diluta a subspecies found throughout northern and central Asia, and R. r. shelleyi, found from Egypt to northeastern Africa. (Garrison, 1999)
Bank swallows are smallish swallows with grayish-brown plumage on the head, back, wings, and tail. The flight feathers of the wings and tail have a slightly darker plumage color and there is a brown band that stretches across the breast. The chin, throat, belly, and undertail coverts are white. Juveniles may have buffy or whitish upperparts and a pink wash to the throat. Their tails are slightly notched. (Garrison, 1999)
Bank swallows can be confused with other, small brownish swallows. In North America this includes northern rough-winged swallows (Stelgidopteryx serripennis), which lacks the breast band, and juvenile tree swallows (Tachycineta bicolor), which are larger and differ in some plumage characteristics. In South America they may be confused with brown-chested martins (Progne tapera), which are much larger (30-40 g). Bank swallows may also be distinguished by their voice and their flight pattern: they hold their wings at a sharp angle in flight and use quick, flicking wing beats. (Garrison, 1999)
Average daily metabolic rates for bank swallows have been measured at 8.99 to 11.55 cm3 CO2/g/hr. (Garrison, 1999)
Bank swallows are monogamous and defend their nesting site together. Males begin to excavate burrows when they arrive on their breeding grounds. Preferred burrow sites are in soft, but stable soils, most often higher on banks or slopes. Burrows are dug perpendicular to the bank face and average 58.8 cm in length when complete. Once the nest burrow is about 30 cm long, they will begin to sit in the entrance and sing to attract females. They will also perform flight displays outside of the burrow entrance to attract females. The pair bond is formed as a female begins to sing in response to the male and perch near the burrow. Males and females will sleep together in the nest burrow and most copulations occur there. (Garrison, 1999)
Both sexes, however, will attempt extra-pair copulations. Male bank swallows assess female mass via flight characteristics, such as speed of ascent, in order to determine which females are most likely to be in a pre-laying or laying condition. Females that are heaviest are also at their most fertile condition, making them the best targets for attempts at extra-pair copulations. However, both sexes also guard their mates so extra-pair copulations may not be terribly common. (Garrison, 1999; Jones, 1986)
Once a mated pair is formed at an excavated burrow, females will begin building a nest in the burrow, along with helping with any additional excavation. Nests are lined with grass, feathers, and other fine materials in the area. Females begin to lay eggs as early as April and into July in some areas. Most pairs attempt only 1 clutch per year, unless their first clutch is destroyed early in the nesting season. Females lay from 1 to 9, but usually 4 to 5, white eggs every day until the full clutch size is reached. Females begin incubating the clutch 1 to 2 days before all eggs are laid. Incubation takes 13 to 16 days and eggs hatch over the course of several days. Hatching in colonies is generally synchronous. Fledging occurs at around 20 days after hatching and parents continue to feed their young for 3 to 5 days after fledging. Once they become independent, young bank swallows gather in flocks of juveniles and adults. They are forced away from their natal burrow by their parents, but often gather in small groups at other burrows to rest. Males and females can breed in their first year after hatching. (Garrison, 1999)
Male and female bank swallows share in incubating young, which allows them to lay eggs earlier in the season, when the weather is colder, than other swallow species (Hirundinidae) in which females only incubate eggs (such as Hirundo rustica). However, females do most incubation. Both parents sleep in the nest burrow at night. Young are altricial at hatching and parents brood them for 7 to 10 days. Both parents feed the young and help to protect them from predators until they are 23 to 25 days old, a few days after they have left the nest burrow. (Garrison, 1999; Turner, 1982)
The yearly recruitment of bank swallows may be strongly influenced by conditions in the wintering habitat, which influence survival of juveniles. A study of a Hungarian population that winters in the Sahel region of Africa, suggested that winter, Sahelian rainfall was related to adult population size in the following year on the breeding range. Average annual mortality estimates for adults are approximately 60%, mortality in juveniles is higher. Two bank swallows lived to 9 years old in the wild. (Garrison, 1999; Szep, 1994)
Bank swallows are susceptible to the effects of unseasonably cold weather, which makes it difficult for them to find insect prey and meet their energy demands. Nestlings also die when burrows collapse. (Garrison, 1999)
Bank swallows are gregarious, living and breeding in colonies. Although colonial living has been demonstrated to increase exposure to parasites and increase levels of competition for food, nesting resources, and mates, bank swallows that live in larger colonies are more successful at detecting and defending against diurnal avian predators. Bank swallows may engage in communal preening and roosting. They will also sunbathe in groups. They are very social and will roost in direct contact with others. Bank swallows will cooperate to mob predators and may forage together. (Hoogland and Sherman, 1976)
Bank swallows migrate fairly long distances, often in flocks with other swallows (Hirundinidae). They arrive on their breeding grounds in early spring and leave in late summer. On their winter range, bank swallow populations may be nomadic. Migration seems to occur primarily along waterways. They forage from early in the morning through dusk. Like most swallows (Hirudinidae), bank swallows are fast and agile in flight. Their flight is described as "fluttery," with rapid wing beats and short glides. Their wings are held bent in flight, unlike most other swallows. They will forcefully hit, and then bounce off of, the surface of water to drink, gather nesting material, grab an insect, or bathe themselves. Bank swallows are ungainly on the ground and are mainly seen perching or in flight. (Garrison, 1999)
Nesting pairs defend only their nest burrow and the area immediately around the burrow. Home range sizes are not reported. (Garrison, 1999)
Young bank swallows use a food-begging call and a signature call to their parents at the nest. Parents recognize the calls of their own offspring. Parents respond with a feeding call when they return to the nest to feed their young, the feeding call is described as a set of sweet notes. Contact calls are the most commonly used call and are described as a raspy or strident "tschr." Males also sing to advertise territories and attract females for mating. Males can sing at the nest and in flight. The song sounds like a rapid repetition of the contact call, giving it a chattering quality. Bank swallows also use warning and alarm calls when they observe predators. Warning calls are given to colony-mates while alarm calls are directed at predators when they are being mobbed. (Garrison, 1999)
Males also perform display flights to attract females. (Garrison, 1999)
Bank swallows eat almost exclusively insects that they catch in flight. Insect prey are generally flying insects, although occasionally they take terrestrial or aquatic insects or insect larvae. Most foraging occurs over bodies of water or large areas of short-growing vegetation, such as meadows, agricultural fields, or wetlands. They sometimes forage over forest canopies. Bank swallows drink in flight as well, by skimming the water surface with their lower mandible. The size of colonies may impact whether individuals can get information on the location of prey from other individuals. In North America, swallows in relatively small colonies (5-55 pairs) did not transmit information on foraging to others. In Hungary, however, swallows in a large colony (2100 pairs) foraged synchronously and seemed to transmit information on foraging to other colony members. Breeding adults generally forage within 200 m of their nest, although they may have to forage farther away. If foraging distances are higher, parents return to nests with larger food boluses. (Garrison, 1999; Hoogland and Sherman, 1976)
Bank swallows forage from dawn to dusk. One study of stomach contents suggested 99.8% of bank swallow diet is insects, with approximately 33.5% ants, bees, and wasps (Hymenoptera), 26.6% flies (Diptera), 17.9% beetles (Coleoptera), 10.5% mayflies (Ephemeroptera), 8% bugs (Hemiptera), 2.1% dragonflies (Odonata), and 1.2% moths and butterflies (Lepidoptera). Other studies yielded similar results, although proportions of prey varied by region and season. (Garrison, 1999)
Bank swallows that live in larger colonies are better able to detect and defend against avian predators. They cooperate to mob predators that threaten their colony. Most predation is on nestlings and eggs in burrows. Eurasian badgers (Meles meles) have been observed excavating burrows and it is likely that other terrestrial mammals attempt to take advantage of bank swallow colonies. Snakes are important predators of nestlings, including gopher snakes (Pituophis melanoleucus) and black rat snakes (Pantherophis obsoletus) in North America. American kestrels (Falco sparverius), hobbies (Falco subbuteo), and other bird-specialist raptors will attempt to take flying adults and inexperienced fledglings. Bank swallows are often unsuccessful in deterring predators via mobbing. They have been observed deterring predation by blue jays (Cyanocitta cristata), however. (Garrison, 1999; Hoogland and Sherman, 1976)
Bank swallows that live in larger colonies suffer higher rates of flea infestation and nestlings with fleas had lower body masses than nestlings without fleas. Flea species include Ceratophyllus styx, Celsus celsus, and Ceratophyllus riparius. Larval blowflies parasitize bank swallows as well, including Protocalliphora splendida, Protocalliphora braueri, Protocalliphora hirundo, Protocalliphora metallica, Protocalliphora sialia, and Protocalliphora chrysorrhoea. This last species seems to be restricted to the nests of bank swallows throughout the Holarctic. Mites (Liponyssus sylviarum, Atricholaelaps glasgowi), lice (Myrsidea dissimilis), feather lice (Mallophaga), and nematodes (Acuaria attenuata) are also found in bank swallows. (Garrison, 1999; Hoogland and Sherman, 1976)
Bank swallows are important predators of flying insects, especially where they concentrate around breeding colonies. European starlings and house sparrows may take over their burrows. Other sand and bank burrowing birds, such as kingfishers, barn owls, northern rough-winged swallows, and cliff swallows are tolerated by bank swallows. (Garrison, 1999)
Through their predation on flying insects, bank swallows can help to control populations of pest insects, such as mosquitoes and agricultural pests. (Garrison, 1999)
There are no known adverse effects of bank swallows on humans.
Bank swallows are widespread and population sizes are large. The IUCN considers them "least concern." However, local populations are impacted by loss of nesting habitat. In California they are listed as threatened, they are considered sensitive in Oregon, and a species of special concern in Kentucky. Bank swallows are fairly tolerant of human activities and will even nest in active quarries. (BirdLife International 2008, 2008; Garrison, 1999)
Tanya Dewey (author), Animal Diversity Web.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
active at dawn and dusk
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
BirdLife International 2008, 2008. "Riparia riparia" (On-line). IUCN Red List of Threatened Species. Accessed April 01, 2009 at http://www.iucnredlist.org/details/147936.
Garrison, B. 1999. Riparia riparia. Birds of North America, 414: 1-20. Accessed March 30, 2009 at http://bna.birds.cornell.edu.proxy.lib.umich.edu/bna/species/414.
Hoogland, J., P. Sherman. 1976. Advantages and disadvantages of bank swallow (Riparia riparia) coloniality. Ecological Monographs, 46: 33-58. Accessed March 30, 2009 at http://www.jstor.org/pss/1942393.
Jones, G. 1986. Sexual chases in sand martins (Riparia riparia): cues for males to increase their reproductive success. Behavioral Ecology and Sociobiology, 19: 179-185.
NatureServe 2008, 2008. "Riparia riparia" (On-line). NatureServe Explorer 2008. Accessed March 30, 2009 at http://www.natureserve.org/explorer/.
Szep, T. 1994. Relationship between west African rainfall and the survival of central European Sand Martins Riparia riparia. Ibis, 137: 162 - 168.
Turner, A. 1982. Journal of Animal Ecology. Timing of laying by swallows (Hirundo rustica) and and sand martins (Riparia ripari), 51: 29-46.