The bank swallow, also known as the sand martin in Eurasia, is a small passerine bird in the swallow family. Its scientific name is Riparia riparia.
Overview of the Bank Swallow
The bank swallow is a migratory bird that breeds in northern areas of Europe, Asia and North America and winters in southern Europe, Africa and South America. It is found near rivers, lakes, and other water bodies where there are vertical, sandy banks or cliffs with holes suitable for nesting. Bank swallows nest in colonies ranging from several to a few thousand pairs.
Bank swallows typically construct nest burrows in earthen banks. The burrows are dug by both males and females, and are usually about 2 feet deep. They nest in aggregations with up to several thousand pairs forming dense colonies.
These birds feed primarily on insects, which they catch in flight over water or open country.
Bank swallows are small birds, measuring about 5 inches in length and weighing approximately 0.4 to 0.5 ounces. They have brown upperparts, white underparts, a brown breast band, and a forked tail. The sexes are similar in appearance.
Their distinctive nesting habits gave rise to the species name riparia, which means “of the riverbank” in Latin. The genus name Riparia also reflects this.
Scientific Classification
The bank swallow is classified in the kingdom Animalia, phylum Chordata, class Aves, order Passeriformes, family Hirundinidae, genus Riparia, and species R. riparia.
Here is a summary of the scientific classification:
Kingdom | Animalia |
---|---|
Phylum | Chordata |
Class | Aves |
Order | Passeriformes |
Family | Hirundinidae |
Genus | Riparia |
Species | R. riparia |
Kingdom Animalia
Bank swallows belong to the kingdom Animalia, which includes all multicellular eukaryotic organisms that obtain energy through digestion. Animals are heterotrophic organisms that lack cell walls and have differentiated tissues and organs.
Phylum Chordata
The bank swallow is classified in the phylum Chordata. All chordates are deuterostomes possessing a notochord, a hollow nerve cord, pharyngeal slits, and a post-anal tail during at least one point in their development. Vertebrates are the most familiar group of chordates.
Class Aves
This species belongs to the class Aves, which includes all birds. Birds are endothermic vertebrates distinguished by feathers, toothless beaked jaws, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton.
Order Passeriformes
Bank swallows belong to the diverse order Passeriformes. Passerines comprise over half of all bird species, including familiar birds such as perching songbirds, crows, wrens, and swallows. They are characterized by three toes pointing forward and one toe pointing backward.
Family Hirundinidae
This swallow species is a part of the family Hirundinidae, known as the swallows and martins. This family includes around 75 species of passerines characterized by their adaptation to aerial feeding.
Genus Riparia
The bank swallow is placed in the genus Riparia, which includes eight species of swallows commonly known as bank swallows. The genus name Riparia is derived from the Latin word meaning “of the riverbank,” referring to their habitat.
Species R. riparia
The specific epithet of the bank swallow is riparia. As noted above, this Latin term means “of the riverbank” and refers to this species’ habit of nesting on riverbanks and similar places.
Naming and Discovery
The bank swallow was first described scientifically by the Swedish naturalist Carl Linnaeus in 1758. In his seminal work Systema Naturae, he gave it the binomial name Hirundo riparia.
The genus name Hirundo is the Latin word for “swallow”. The species name riparia means “of the riverbank”.
In 1825, the Irish zoologist Nicholas Aylward Vigors moved this species to its current genus Riparia. He noted differences in the bill and feet that distinguished it from the barn swallow Hirundo rustica.
No subspecies of the bank swallow are recognized.
Identification
The bank swallow is a small, sparrow-sized bird about 12-13 cm (4.7-5.1 inches) in length and weighing around 14-25 g (0.49-0.88 oz). It has the following physical features:
- Brown upperparts and pale underparts
- Broad brown band on the breast
- White throat and belly
- Short forked tail with white outer tail feathers
- Pale rump
- Black bill and legs
In flight, the short, pointed wings with contrasting pale and dark patterns are characteristic.
The sexes look alike. Juveniles have duller plumage and a paler breast band.
The bank swallow is very similar to the closely related cliff swallow. Differences include:
- Cliff swallow has a square tail rather than forked
- Cliff swallow has an orange forehead and rump
- Cliff swallow breast band is narrower
Geographic Range
The bank swallow has a wide range across the Northern Hemisphere. Its breeding range extends across:
- North America from Alaska to Newfoundland, south to Texas and Florida
- Europe and northern Asia east to the Pacific coast
It is strongly migratory, wintering in:
- Africa
- Central and South America
- South Asia
Habitat
The bank swallow inhabits open country near bodies of water such as rivers, lakes, ponds, and the ocean coast. Its habitat preferences include:
- Riverbanks
- Sand and gravel pits
- Road cuts
- Sea cliffs
- Stock ponds
The key requirements are vertical or near-vertical banks and cliffs with fine-textured or sandy soil suitable for digging nesting holes.
Behavior
The bank swallow exhibits typical swallow-like behavior. Key aspects of its behavior include:
- Fast, agile flight while hunting insects
- Nesting in dense colonies of up to several thousand pairs
- Excavating burrows for nesting
- Migratory habits, traveling between temperate breeding areas and tropical wintering regions
Bank swallows are diurnal and feed mainly on flies, caught on the wing. They spend much of their time flying over water hunting for insect prey.
They are very social, nesting colonially and migrating in flocks of hundreds or thousands of birds. They migrate during the night and roost communally during migration.
Vocalizations
The calls of the bank swallow are typical of the swallow family. Their most common vocalizations include:
- A scratchy twitter given frequently in flight
- A conversational communal twittering at the breeding colony
- A sharp alarm call when predators are spotted
Breeding
Bank swallows breed in colonies ranging from a few to several thousand nesting pairs. In suitable habitat, nests may be placed side-by-side or up to 1 m (3.3 ft) apart.
Both sexes excavate the nest burrow, which averages about 0.5-1 m (1.6-3.3 ft) long and ends in an enlarged nest chamber lined with grasses and feathers.
Clutch size is typically 4-5 eggs that are incubated by both parents for around 14 days. The chicks fledge approximately 22-24 days after hatching.
Bank swallows typically raise one brood per year. They show strong nest site fidelity, often returning to the same colony in subsequent breeding seasons.
Migration
Bank swallows migrate during the night in large flocks. They winter in southern regions including:
- Sub-Saharan Africa
- Northern South America east of the Andes
- South and Southeast Asia
Most populations migrate thousands of miles between their breeding and wintering grounds. Banding studies have demonstrated connections between breeding populations in Alaska wintering in Argentina and Brazil.
Diet
The bank swallow is insectivorous, catching insects in flight. Its diet consists predominantly of flies (Diptera), including mosquitoes, midges and black flies. Other prey include:
- Wasps and bees (Hymenoptera)
- Aphids (Hemiptera)
- Butterflies and moths (Lepidoptera)
- Ants (Formicidae)
- Beetles (Coleoptera)
Foraging occurs mainly over open water, wetlands, or sparsely vegetated areas. The swallows fly back and forth to capture prey.
Population and Conservation
The bank swallow has an extremely large range and population. Its total population is estimated at 190 million adult birds. Trend data from the North American Breeding Bird Survey indicates an overall population increase between 1966-2015. However, some local populations have declined.
Major threats include:
- Habitat loss due to riverbank stabilization, loss of sandy pits, and stock pond management practices
- Pesticides reducing insect prey abundance
- Climate change affecting migration timing and food supply
However, the bank swallow remains common and widespread. Its ability to use artificial habitats like roadcuts has allowed expansion in some regions. The IUCN Red List categorizes this species as Least Concern.
Key Facts
- Scientific Name: Riparia riparia
- Common Name: Bank swallow
- Genus: Riparia
- Species: R. riparia
- Order: Passeriformes
- Family: Hirundinidae
- Habitat: Open areas near water
- Size: 12-13 cm (4.7-5.1 in), 14-25 g (0.49-0.88 oz)
- Diet: Insects caught in flight
- Status: Least Concern
Conclusion
In summary, the bank swallow is a small migratory songbird in the swallow family that breeds in colonies along riverbanks and other wetland areas across the Northern Hemisphere. Its scientific name is Riparia riparia. Closely related to the cliff swallow, it can be identified by its brown collar, forked tail, and burrowing nest sites.
The bank swallow feeds aerial insects and exhibits a highly social lifestyle. Its populations remain robust across its extensive range. However, local declines due to habitat loss point to the need for continued monitoring and conservation of suitable nesting areas for this species.