Both barn swallows and tree swallows are small songbirds in the swallow family Hirundinidae. They can be difficult to tell apart as they have similar coloring and often overlap in range. However, there are some key differences between these two species in terms of physical characteristics, habitat, nesting habits, diet, and behavior.
Physical Characteristics
Barn swallows and tree swallows share a mostly iridescent steel blue back and wings and a pale underside. However, barn swallows can be identified by their long, deeply forked tail and reddish-brown forehead, throat, and upper breast. Tree swallows have a shorter, slightly notched tail and pure white undersides.
| Physical Trait | Barn Swallow | Tree Swallow |
|---|---|---|
| Size | 5.5-7.5 inches long | 5-6 inches long |
| Wingspan | 11.8-15 inches | 11.4-13.4 inches |
| Weight | 0.7 ounces | 0.6 ounces |
| Tail shape | Deeply forked | Slightly notched |
| Head color | Reddish-brown forehead, throat, breast | Iridescent blue-green |
| Belly color | Pale reddish-brown | Clean white |
As you can see, barn swallows are slightly larger than tree swallows on average. Barn swallows also have a more deeply forked, longer tail and reddish-brown coloration on the head that tree swallows lack.
Habitat
Barn swallows and tree swallows use different habitats in the spring and summer breeding season:
- Barn swallows are found in open areas near structures like barns, stables, bridges, etc. where they can nest. They prefer farms, rural areas, and open fields near water.
- Tree swallows are found in more forested areas near water, fields, and marshes. They nest in tree cavities in standing dead trees or nest boxes.
In the winter, barn swallows migrate to the southern US, Mexico, Central America, and South America. Tree swallows migrate shorter distances to the southern US coasts and Mexico.
Nesting
The nesting habits of barn and tree swallows also differ:
- Barn swallows build cup-shaped mud nests on vertical surfaces like barn walls or cliff faces. Their nests have an enclosed, tunnel-like entrance.
- Tree swallows nest in cavities like old woodpecker holes or nest boxes. They do not build an elaborate nest, instead lining the cavity with grasses and feathers.
In addition, barn swallows are very social, often nesting in dense colonies of up to thousands of pairs. Tree swallows nest more solitarily, with nests spaced widely apart even when using nest boxes.
Diet
Both species feed primarily on insects caught during continuous flight. However, they tend to target different types of insects:
- Barn swallows prey on open-air insects like flies, bees, wasps, and aerial spiders.
- Tree swallows eat more winged insects found over water and fields like dragonflies, damselflies, moths, butterflies, and beetles.
This difference in diet is influenced by their different foraging habitats. Barn swallows hunt over open areas and can catch faster flying prey. Tree swallows forage near wetlands and forests and take slower insects.
Behavior
We can also observe some behavioral differences between barn and tree swallows:
- Barn swallows are very social year-round, gathering in large flocks when not breeding. Tree swallows are more solitary outside of the breeding season.
- Barn swallows perform elaborate swooping courtship flights. Tree swallow courtship mainly involves vocalizations.
- Male barn swallows defend nesting areas from intruders. Male tree swallows are more defensive of their mate rather than a territory.
- Barn swallows commonly have 2 broods per year. Tree swallows rarely have more than 1 brood per year.
So in summary, barn swallows are more aggressive and social compared to tree swallows.
Song and Calls
We can distinguish these species by differences in their vocalizations as well:
- Barn swallow song is a pleasant twittering warble ending in harsh trills.
- Tree swallow song is a series of clear whistles and chirps, slower and more musical than the barn swallow.
Barn swallow calls are raspy and scolding. Tree swallow calls are softer ringing and rattling notes.
Similar Species
While barn and tree swallows overlap across much of North America, there are some other similar-looking species found only regionally that should also be considered:
- The violet-green swallow of the west coast is larger with white sides to its tail rather than just white corners.
- The golden swallow of the southwest has a longer, bright blue tail and yellow throat and forehead.
- The Bahama swallow of Florida has a shorter tail and darker red-brown breast band.
However, none of these species overlap in range with both barn and tree swallows, making identification easier if you have a known location.
Conclusion
In summary, barn and tree swallows can be challenging to differentiate by sight alone. However, paying attention to subtle differences in size, tail shape, head color, habitat, behavior, and song makes identification much easier. With practice, birders can learn to recognize these species in the field more confidently. Getting a good look at the tail and head coloration provides the best clues for telling barn swallows and tree swallows apart.
