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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, 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 expected 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 swallowtails 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 nest boxes we humans set up around water. 

  • Barn swallows build mud nests on the ceilings of human structures such as… barns, boardwalks, and bridges. 

  • Rough-winged swallows nest in holes in riverbanks or artificial holes such as drainage pipes and crevices in bridges. 




Swallows mostly eat insects, generally flying ones 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. 


Observing Swallows


Swallows are easy to observe. They hunt close to the surface above waterways and open, grassy areas. Stand still; they might buzz you, swooping a few feet away as they pursue bugs. 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 declined, possibly due to insecticides working their way up the food chain and possibly to insect biomass declines. 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 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.


More Resources


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 about swallows and other birds. 

Lots of birds catch bugs over water. Learn about where those bugs come from and the links between the creatures of the water and the air. Thanks to our partners at Grid Magazine for producing the video and to the William Penn Foundation for their support. 

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. 

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