Several types of birds, including most varieties of swallows, warblers and other songbirds, consume flying insects—including mosquitoes. Mosquito-eating birds feed during the day, while in flight. Maintaining a backyard or other outdoor area that attracts them can help keep the mosquito population down. Nevertheless, bird predators alone don’t substantially reduce mosquitoes simply because mosquitoes make up only a small part of their diet.
Purple Martins are the biggest birds in the swallow family, and they're commonly thought of as prolific mosquito consumers. Their diet is made up of a large variety of flying insects, which they eat while on the wing. They eat their weight in insects on a daily basis. Their diet can include, but isn’t limited to, flies, bees, wasps, dragonflies, moths, butterflies, flying ants and mosquitoes. According to purplemartin.org, several papers published between 1918 and 1967 assert that the Purple Martin eats as many as 2,000 mosquitoes a day—claims that have since been denounced as unfounded. While martins will feed on mosquitoes, they typically spend their feeding time flying much higher than mosquitoes do, and therefore don’t come in contact with them enough to turn them into a large meal. However, during twilight hours, as more mosquitoes emerge and Purple Martins fly closer to the ground, there’s more of a chance the two will cross paths. So, although martins will eat mosquitoes, they shouldn’t be considered an effective form of mosquito control.
Barn Swallows, like their relative the Purple Martin, also consume mosquitoes, among other flying insects. Barn Swallows in particular are known for their graceful flight patterns as they dive and swoop to catch their prey. Unlike certain other birds that feed by flying with their mouths open in an attempt to catch what they will, Barn Swallows go after their prey one insect at a time, resulting in what bird watchers call “aerial acrobatics”. Barn Swallows tend to feed at lower heights than Purple Martins and therefore come across more mosquitoes. However, mosquitoes are small and swallows must eat their weight in insects on a daily basis. Because they feed selectively, they tend to go for larger insects such as flies, dragonflies or flying ants. Linda deKort, writing for the Flathead Audubon Society, states that “…insects make up 99.8 percent of the swallow’s diet. A single Barn Swallow can consume 60 insects per hour or a whopping 850 per day.”
Blackpoll Warblers are small songbirds that breed in northern Canada, winter in the northern part of South America and migrate across the eastern and Midwestern United States. Unlike the birds in the swallow family, these songbirds consume a wide variety of food. Their diet consists primarily of arthropods, which are animals or insects with segmented bodies and jointed legs, such as centipedes, millipedes, spiders and lice. Warblers also eat fruit, seeds and other insects, including flying insects such as gnats, flies and mosquitoes. As with swallows, Blackpoll Warblers shouldn’t be considered a primary source of mosquito control. In the warbler’s case, the bulk of their diet comes from culling insects from the underside of leaves or branches. Nevertheless, according to borealbirds.org, Blackpoll Warblers will eat during flight, or by “hovering or hawking.”