Tree swallows and bank swallows are two similar-looking species of swallows found in North America. While they occupy similar habitats and eat similar foods, there are some key differences between juvenile tree swallows and bank swallows.
Appearance
The most noticeable difference between juvenile tree swallows and bank swallows is their plumage. Juvenile tree swallows have dull brownish upperparts and pale underparts. Their wings and tail are also dull brown. Juvenile bank swallows have pale gray-brown upperparts and off white underparts. Their wings and tail are also pale brown.
Both species develop more colorful plumage as adults, with iridescent blue-green upperparts. But juvenile plumage of the two species is distinctive. Tree swallows have a duller, warmer brown appearance compared to bank swallows.
Size
Tree swallows are slightly larger than bank swallows. Juvenile tree swallows average about 5.5 inches in length with a wingspan around 11 inches. Juvenile bank swallows are smaller, averaging 5 inches in length with a 10 inch wingspan.
Bill Shape
The bill shape differs between the two species. Tree swallows have a shorter, stouter bill that is black. Bank swallows have a longer, more pointed bill that is blackish-brown. This difference in bill shape reflects their different feeding behaviors.
Range
Tree swallows have a broader breeding range across North America than bank swallows. Tree swallows breed across Alaska, Canada, and the continental United States. Bank swallows have a more restricted breeding range concentrated in western North America.
So juvenile tree swallows occupy a wider geographic range than juvenile bank swallows. Their environment and food sources during development differ across this range.
Habitat
The preferred nesting habitat of the two species differs. Tree swallows typically nest in tree cavities in open areas near water. Bank swallows nest in colonies in burrows dug into earthen banks, usually along rivers and streams.
So juvenile tree swallows and bank swallows are raised in very different nest environments as they develop. This contributes to differences in their behavior and skills.
Diet
Both species are aerial insectivores, feeding on flying insects. But tree swallows are able to utilize a broader range of habitats for feeding than bank swallows. Tree swallows regularly forage over open fields, forests, and wetlands. Bank swallows concentrate feeding over water.
This can contribute to differences in the exact diet composition of juveniles, as they are raised on what parents bring back to the nest. Tree swallows may eat a wider diversity of insects.
Flocking Behavior
In the nonbreeding season, tree swallows and bank swallows show different flocking habits. Tree swallows form massive mixed flocks with other swallows and songbirds. Bank swallows form smaller flocks that remain closely tied to bodies of water.
Juvenile tree swallows likely start learning these flocking behaviors from their parents and other adults early on. So juvenile tree swallows and bank swallows develop different socialization.
Migration
Tree swallows and bank swallows also differ in their migration distances. Tree swallows are short to medium distance migrants, wintering primarily in the southern U.S and into Mexico. Bank swallows are long distance migrants that winter mainly in Central and South America.
The longer migration of bank swallows means juveniles must develop stronger flight endurance before they migrate compared to tree swallows. Their development is geared toward these different migration needs.
Trait | Juvenile Tree Swallow | Juvenile Bank Swallow |
---|---|---|
Plumage | Dull brownish upperparts, pale underparts | Pale gray-brown upperparts, off white underparts |
Size | 5.5 inches long, 11 inch wingspan | 5 inches long, 10 inch wingspan |
Bill shape | Short, stout, black bill | Longer, pointed, blackish-brown bill |
Range | Broad across North America | Concentrated in western North America |
Habitat | Tree cavities in open areas near water | Colonial burrows in earthen banks of rivers and streams |
Diet | Broad range of aerial insects | Concentrated on insects over water |
Flocking | Mixed large flocks | Smaller flocks near water |
Migration | Short to medium distances | Long distances to Central and South America |
Behavioral Development
The differences in habitat, diet, social behavior, and migration between the two species also shape important differences in their behavioral development as juveniles.
Juvenile tree swallows must develop skills for catching insects over diverse habitats. Juvenile bank swallows hone their insect foraging skills specifically over water.
Juvenile tree swallows practice flocking with other species from a young age. Juvenile bank swallows focus on flocking with their own species.
Juvenile bank swallows likely have a stronger innate drive and ability for long distance migration compared to tree swallows. Parents and other adults pass on knowledge of distant wintering grounds.
Conclusion
While juvenile tree swallows and bank swallows appear generally similar as young fledglings, they differ in important aspects like plumage, size, bill shape, geographic range, and habitat. These differences drive development of distinct skills and behaviors related to feeding, flocking, and migration in the two species. Paying attention to subtle differences in appearance and behavior can help identify whether a juvenile swallow is a tree swallow or a bank swallow.