Bank Swallow (Riparia riparia)
prepared Brendon Samuels, Coordinator, London Bird Team. August 19, 2021
The Bank Swallow belongs to a category of birds called aerial insectivores, along with swifts, martins and other swallows, that primarily eat insects while in flight. Bank Swallows are the smallest species of swallow in North America. They are highly aerodynamic in flight, plain in their appearance but with a charismatic life history. The Bank Swallow's plumage is rich brown above and white below, featuring a distinctive brown band across the chest. The song of the Bank Swallow is a soft, rapid jumble of raspy notes.
Listen to the song (left) and call (right) of the Bank Swallow below:
Bank Swallows are one of the most widely distributed bird species in the world. Elsewhere, Bank Swallows are known as Sand Martins. Over the past 40 years, Bank Swallows have declined by 98% across Canada and by 93% within Ontario.
North America’s Bank Swallows overwinter in the southern United States, Mexico and the Carribean, flying thousands of kilometers northward each spring to return to Canada where they breed. Each year, Bank Swallows gather in colonies to painstakingly excavate nest burrows using their tiny feet and beak as well as their wings. During breeding, Bank Swallows stick close to their nesting colony, foraging for flying insect prey.
Swallows can eat 25-50% of their body mass in a day, frequently feeding on human, livestock and agricultural pests, including mosquitoes, horseflies, stable flies and weevils. In other words, these birds provide natural insect control!
Bank Swallows in London, Ontario
Bank Swallows have been documented by birders and scientists in London, Ontario dating back many decades. The Zoological Collections at Western University include specimens of Bank Swallows that were collected on the campus grounds over half a century ago! eBird records for the Bank Swallow in London date back to 1925. The London area provides critical habitat for Bank Swallows because of its proximity to the Thames River. Bank Swallows can frequently be observed in Springbank Park, Kilally Meadows, the Sewage Lagoons in Strathroy and elsewhere along the river.
In the past, bank swallows were commonly found around natural bluffs or eroding banks along streams. Today, due to habitat loss caused by urban sprawl, agricultural land use and accelerated erosion, Bank Swallows are often forced to dig their burrows in human-made sites such as sand and gravel quarries or road cuts. Within Ontario over half of the provincial population of Bank Swallows now breed in aggregate pits and quarries.
The largest known breeding colony of Bank Swallows in the London area is located in the Byron Gravel Pit in London West. According to an estimate from 2020, the Byron colony is home to almost 2,000 birds! Check out the extent of the colony in the panorama below:
The Bank Swallow colony in the Byron Gravel Pit in London West is home to almost 2,000 birds. Each dark spot represents a nest burrow excavated by an adult breeding pair. According to Bank Swallow biologists, approximately half of the nest burrows at a given site will be active each year. Photo by Brendon Samuels, June 2020, London, ON.
Bank Swallow numbers in Canada have declined by more than 90%. The Bank Swallow was designated as Threatened in Ontario 2014.
A variety of factors are contributing to the decline of Bank Swallows, including:
Food supply. Due to pesticide use, the expanding urban footprint, industrial agriculture, loss of wetlands and woodlands, and other factors, insects in the air are less abundant than they once were.
Breeding habitat. Landscapes that were traditionally used by Bank Swallows for constructing nest burrows, such as banks along bodies of water, have disappeared because of accelerated erosion, agricultural land use and urban development. Attempts to construct artificial breeding structures for Bank Swallows have proven mostly unsuccessful.
Extreme weather. Torrential rains and cold snaps can cause nest burrows to collapse and disrupt the food supply.
Help make London friendlier for Bank Swallows:
Advocate for the preservation of lands used by Bank Swallows for breeding, including aggregate lands like the Byron Gravel Pit in London West
Support the protection of natural habitats, which produce insects that waft upward for birds to eat.
Grow native plants in your yard to help support caterpillars and other insect stages that, as adults, may travel skyward to become food for swallows; encourage friends and neighbours to do the same.
Avoid use of pesticides and reduce your ecological footprint as much as possible.
Monitor construction dirt piles for Bank Swallow burrows during spring and summer. If Bank Swallow activity is discovered at an active construction site, please contact the Ontario Natural Heritage Information Centre OR submit a record using eBird or iNaturalist.
Bank Swallows in flight. Recorded at the Byron Gravel Pit by Brendon Samuels in June 2020, London, ON.
Bank Swallows approaching their nest burrows. Video is slowed down by 50 percent. Recorded at the Byron Gravel Pit by Brendon Samuels in June 2020, London, ON.