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From the Archives: Barn Swallows

From the June 2016 Newsletter, by Julie Dyer (former Biodiversity Apprentice, student at Dalhousie University)

Barn Swallows are aerial insectivores – birds that feed on flying insects. This group of birds (which includes swifts, swallows, flycatchers, and goatsuckers) is experiencing alarming population declines across Canada, and are particularly severe in northeastern North America. Barn Swallows are the most widely distributed and abundant swallow in the world. These birds play an important role in pest management, eating hundreds of insects each day! Although Barn Swallows are still common, the population in Canada declined by about 30% between 1999 and 2009. Barn Swallows have been recommended for protection under Canada’s Species at Risk Act. They are most widely distributed species of swallow in the world, found on every continent except Antarctica. The Barn Swallow is a Project NestWatch Focal Species, and accepts data on all nesting birds in Canada.


The Barn Swallow’s threats to survival include; Predation by Barn cats, rats, mice, owls, and raptors, Nest destruction and nest parasitism by other species, such as House Sparrows, Brown-headed Cowbirds, and Cliff Swallows, Ectoparasites, like mites and blowflies, and Human causes. Because Barn Swallows nest in close proximity with humans, nests may fail due to intentional disturbance or destruction, or unintentional disturbance from human activities near the nest.

Barn Swallows can be identified by their blue back, wings and tail, chestnut throat and forehead, and pale underparts. They are easily distinguished from all other swallow species in North America by their long forked tail. Males and females are similar, though males tend to be darker and have longer outer tail-streamers.

Barn Swallows nest in and around human-made structures such as barns, sheds, and boathouses, as well as under bridges and in culverts. They choose structures with an overhang to provide protection, a ledge (can be as small as a wire or nail) to support the nest, and a vertical wall to which it can be attached. Some Barn Swallows nest singly, but many are found in small colonies (usually containing no more than 10 nests). They nest in locations close to foraging habitat and sources of mud (which they use to build their nests).

Nest construction takes an average of one to two weeks, but nest sites and old nests are often re-used. Nests are constructed from mouthfuls of wet mud mixed with grasses and lined with grass, animal hair, and feathers (usually white). Old nests are ‘renovated’ with new mud and new lining each year.

Nests are often adhered to vertical surfaces near the ceiling, or under eaves on the outside of buildings. Barn Swallows also build nests on horizontal beams, or on top of ledges, light fixtures, cables, etc. which provide additional support for the nest. To find nests in a barn or shed, use a flashlight to scan rafters and other areas near the ceiling that could be used to support a nest. In two-story barns, the majority of nests are usually found in the lower level.


You can minimize disturbance by always moving slowly and carefully around nests, do not touch the nests, eggs or young, do not approach within about 5m of nests with visible young, do not spend more than an hour checking nests in a colony (half an hour in cooler weather or rainy conditions), and minimize your time at the nest and photos taken.

By monitoring Barn Swallow nests near you and submitting observations to Project NestWatch, you can contribute to a growing database of information that will help the scientific community understand Barn Swallow declines.

Installing a nest box on your property is a great way to start nest watching! You can create an ideal nesting habitat by creating a food source, like installing insect feeders, create a mud source, leave barn and shed doors and windows open at all times, and putting up nest cups or shelves in barns or below overhangs may attract nesting swallows to your property. Ledges or nest cups should be at least 8-10 cm wide, and placed 15 cm below the ceiling.

You can replace old habitat by constructing artificial nesting structures as old buildings deteriorate and are demolished. If you build your structure at least one breeding season before the old structure is taken down, the young of the year can have a look before fall migration. The structure should include a vent near the ceiling to moderate temperature, and have sides low enough to protect nests from winds and precipitation. Protect nests from predators by placing metal flashing on each leg of the structure, and placing nest cups at least 8 feet above the ground.

Our friends at CPAWS New Brunswick are holding a community screening of The Messenger, a documentary about the plight of songbirds, on March 14th, 2017. We encourage you to join them and learn more about the birds who enhance our lives through their songs!

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