Barn Swallows are fascinating birds, known for their aerial acrobatics and distinctive forked tails. They are widespread across the Northern Hemisphere, adapting to various open environments. This article delves into their preferred habitats, dietary habits, intricate nesting behaviors, and the conservation efforts surrounding this species.
Habitat
Barn Swallows are highly adaptable birds, frequenting open areas across the continent. Their preferred habitats include suburban parks, ball fields, agricultural fields, and beaches. They are also commonly found over open water bodies like lakes, ponds, and coastal waters. These birds can thrive at elevations ranging from sea level up to 10,000 feet. Crucially, their breeding habitat must offer open spaces for foraging, suitable structures or cliffs for nest building, and readily accessible sources of mud, essential for nest construction.
Food
The diet of the Barn Swallow primarily consists of flies, making up the largest portion of their intake. They also consume a variety of other flying insects, including beetles, bees, wasps, ants, butterflies, and moths. Barn Swallows tend to target relatively large, individual insects rather than small swarms. To aid digestion and supplement their diet, they will sometimes ingest grit, small pebbles, eggshells, or oyster shells. These additions may help with processing insects or provide essential calcium.
Nesting
Nest Placement
Barn Swallow pairs are meticulous when selecting a nesting site. They often explore multiple locations, hovering to assess suitability before making a final choice. Ideal nesting spots are typically found under the eaves, rafters, or cross beams of structures such as barns, sheds, and stables. They also readily utilize undersides of bridges, wharfs, and culverts. Barn Swallows may reuse nests from previous years, provided they are not heavily infested with parasites.
Nest Description
Both male and female Barn Swallows collaborate in building their nests, which are constructed from mud. They collect mud in their bills, often mixing it with grass stems to form sturdy pellets. The initial stage involves building a small shelf, followed by the construction of the nest’s sides. When built against a vertical surface, such as a wall, the nest takes on a semicircular, half-cup shape. Nests built on horizontal surfaces, like beams, form a complete cup approximately 3 inches wide and 2 inches deep. The interior of the cup is lined first with grass and then with feathers. In colonial nesting situations, it’s not uncommon for birds to pilfer lining materials from neighboring nests. To maintain their nests, Barn Swallows will clean out old nesting material and add fresh mud to the rim.
Nesting Facts
| Clutch Size: | 3-7 eggs |
|---|---|
| Number of Broods: | 1-2 broods |
| Egg Length: | 0.6-0.8 in (1.6-2.1 cm) |
| Egg Width: | 0.5-0.6 in (1.2-1.5 cm) |
| Incubation Period: | 12-17 days |
| Nestling Period: | 15-27 days |
| Egg Description: | Creamy or pinkish white, spotted with brown, lavender, and gray. |
| Condition at Hatching: | Eyes closed, naked except for sparse tufts of pale gray down. |
Behavior
Barn Swallows are easily recognizable by their smooth, fluid wingbeats and the distinctive retraction of their wingtips at the end of each stroke. They are almost exclusively aerial foragers, flying at lower altitudes than many other swallow species, often close to the ground or water surface. Their hunting grounds are above fields, marshes, lakes, and coastal waters, where they snatch insects mid-flight. They are known to follow farm machinery, livestock, and even humans to catch insects that are flushed out. Occasionally, they will feed on slow-moving or dead insects found on the ground, and in colder weather, they may pluck flies directly off barn walls. Barn Swallows also drink and bathe on the wing, dipping down to scoop water or briefly touch their bellies to the surface for a quick rinse. Males actively defend a territory around the nest, aggressively chasing away rivals, sometimes engaging in physical altercations. Both individuals and groups will mob predators, such as hawks, gulls, or grackles, that venture too close to their nests.
Conservation
The Barn Swallow population has experienced a gradual decline. According to the North American Breeding Bird Survey, populations decreased by approximately 0.6% annually between 1966 and 2019, resulting in a cumulative reduction of about 25%. Partners in Flight estimates the global breeding population at 190 million individuals and assigns them a Continental Concern Score of 8 out of 20, indicating a species with low conservation concern. Historically, Barn Swallows were hunted for the millinery trade in the nineteenth century and are still hunted for food in some wintering areas. A potential threat arises when Barn Swallows incorporate discarded twine or fishing line into their nests; these materials can entangle and trap both adults and young. However, the species has also benefited significantly from human-made structures, and people often encourage these attractive, insectivorous birds to nest nearby. This human association has contributed to a considerable expansion of their breeding range and numbers across the continent.
Credits
Brown, Charles R. and Mary B. Brown. (1999). Barn Swallow (Hirundo rustica), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye (1988). The Birder’s Handbook. A Field Guide to the Natural History of North American Birds, Including All Species That Regularly Breed North of Mexico. Simon and Schuster Inc., New York, NY, USA.
Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.
Myers, G. R. and D. W. Waller. (1977). Helpers at the nest in Barn Swallows. Auk 94:596.
Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.
