Swallows are the trick pilots of the bird world. They fly with deep, liquid wingbeats, suddenly dodge hard to grab a juicy caddisfly out of the air, and then bank hard and up into the air to reverse direction.
Swallows are often best identified by how they fly. Other birds catch insects out of the air - flycatchers wait on their perch and then zip out and back; swifts glide and bank a little more stiffly and higher up in the air - but no others fly with this kind of daredevil quickness and agility.
Three species of swallows are common in Philadelphia (a few others show up too in smaller numbers):
Tree swallows have iridescent, malachite blue backs and clean white bellies.
Barn swallows have cobalt blue backs and tan or reddish-brown bellies. They also have classic swallow tails with long feathers trailing at the corners.
Rough winged swallows are plain by comparison, brown with paler undersides.
All three species can be found over water and other open areas in Philadelphia, though they each choose a different setting for nesting.
Tree swallows nest in cavities in trees or in nest boxes we humans set up for them around water.
Barn swallows build mud nests on the ceilings of human structures such as… barns, as well as boardwalks and bridges.
Rough winged swallows nest in holes in riverbanks or in artificial holes such as drainage pipes and crevices in bridges.
Swallows mostly eat insects, generally flying insects that they catch out of the air.
All three species winter to the south, from the Gulf Coast of the United States down to Central America (rough and tree) or from Central to South America (barn). They show up in the spring once our insects are airborne again.
Swallows, particularly barn and tree swallows, begin migrating south in the summer, sooner than many other migratory birds.
A small group of rough-winged swallows lingers through the winter at the Northeast Water Pollution Control Plant. Midges breed in treated water flowing through open pools towards the Delaware. The swallows stick around and eat the midges.
Swallows are easy to observe. They hunt close to the surface above waterways and open, grassy areas. Stand still and they might buzz you, swooping a few feet away as they pursue bugs. Every now and then they perch to take a break, and you can take advantage of the pause to get a closer look at their plumage.
Rough winged swallows are relatively quiet birds. Barn swallows sing with relatively low squeaky sounds. Tree swallows have a more-chirping song and continue chirping as they fly and hunt.
Living With Swallows
Populations of insect-eating birds like swallows have been in decline, possibly due to insecticides working their way up the food chain, and possibly due to declines in insect biomass. You can help by planting native plants that native bugs know how to live on and reducing insecticide use. More bugs = more birds.
Swallows also feed on insects, such as midges and mayflies, whose nymphs and larvae develop in the water. Taking steps to improve water quality thus also helps birds that depend on these insects.
Nesting tree swallows can be vulnerable to house cats. You can help swallows and many other small animals by keeping cats inside.
Read more about barn, tree, and rough-winged swallows on Cornell’s All About Birds website.
See iNaturalist observations of barn, tree, and rough-winged swallows.
Take a bird walk with BirdPhilly to learn more about swallows and other birds.
Insects like midges and caddisflies whose larvae develop under the water emerge as flying adults... and get snapped up by birds. Learn more about the connection between the worlds of water and air. Thanks to our partners at Grid Magazine for producing the video and to the William Penn Foundation for their support.