Tree swallows are a migratory bird species found throughout much of North America. They breed during the summer months across Canada and the northern United States, and then migrate south to spend the winter along the southern U.S. coastline, Mexico, Central America, and the Caribbean islands. Tree swallows prefer open areas near water, where they can find the insects that make up most of their diet. Let’s take a closer look at the range and habitat where tree swallows are most commonly found.
Breeding Range
Tree swallows breed in open wooded areas and near wetlands across much of Canada and the northern United States. Their breeding range extends from Alaska across Canada to Nova Scotia. It reaches south throughout the northern U.S. states from Washington to Maine.
Some of the states and provinces where tree swallows are most abundant during breeding season include:
- Alaska
- British Columbia
- Alberta
- Saskatchewan
- Manitoba
- Ontario
- Quebec
- New Brunswick
- Nova Scotia
- Maine
- Vermont
- New Hampshire
- Minnesota
- Wisconsin
- Michigan
Within their breeding range, tree swallows seek out open habitats near water. They are drawn to wetlands such as marshes, ponds, lakes, and rivers. Tree swallows also readily nest in wooded areas that are open enough to allow aerial foraging. Some prime nesting spots include forest clearings, parks, golf courses, and agricultural fields.
Wintering Range
In the fall, tree swallows migrate south to their wintering grounds. They can be found along the Atlantic and Gulf coasts from southern New England to Texas. Their winter range also extends along the Mexican coastlines down through Central America, and throughout the Caribbean islands.
Some of the states and regions where tree swallows are most common in winter are:
- Florida
- Coastal South Carolina
- Coastal Georgia
- Alabama Gulf Coast
- Mississippi Gulf Coast
- Louisiana Gulf Coast
- Texas Gulf Coast
- Eastern Mexico
- Yucatan Peninsula
- Central America
- Caribbean Islands
Even on their wintering grounds, tree swallows tend to stick close to open wetland habitats where insect prey is abundant. Coastal marshes, lakes, rivers, and swamps in the southern U.S. and Central America provide ideal overwintering sites.
Year-Round Range
Tree swallows can be found year-round across much of their breeding range. Some individuals, especially younger birds, may not migrate very far south in the winter. They can often be spotted in southern Canada and the northern U.S. throughout the year.
Areas where tree swallows are present year-round include:
- British Columbia
- Washington
- Oregon
- Idaho
- Western Montana
- Minnesota
- Wisconsin
- Michigan
- New York
- Pennsylvania
- Maine
- New Hampshire
- Vermont
Even resident tree swallows that don’t migrate will move around locally between the breeding season and winter. They seek habitats that provide the most abundant insect food sources in each season.
Favorable Habitat
The key unifying feature of areas where tree swallows live year-round, breed, or winter is open habitat near water. This combination provides ideal feeding and nesting conditions. Here are some of the habitats favored by tree swallows:
Marshes
Freshwater and saltwater marshes contain insects like flies, mayflies, dragonflies that tree swallows prey on. Marshes also contain dead trees and erect vegetation that provide nesting sites.
Lakes & Ponds
The open areas around lakeshores and ponds allow tree swallows to spot and aerially hunt insects. Nest boxes can be erected on posts near the water’s edge.
Rivers & Streams
River and stream corridors offer plentiful insects. Tree swallows will nest in old woodpecker cavities in dead trees along river banks.
Parks & Fields
Open grassy areas in parks, pastures, and agricultural fields provide productive hunting for aerial insects. Fence posts and lone trees can serve as nest platforms.
Golf Courses
Manicured golf courses imitate natural open grassland habitat. Tree swallows nest in boxes placed intermittently around the course.
Coastlines
Coastal areas produce swarms of insects. Mangroves and other vegetation along shorelines are used for nesting and roosting.
Population Strongholds
Some areas of North America contain especially large populations of breeding tree swallows. These regions provide expansive wetland habitat.
The Prairie Pothole Region
This area encompasses parts of Alberta, Saskatchewan, Manitoba, and the Dakotas. Shallow wetlands called potholes are abundant across the prairies. Upwards of 70% of the continent’s tree swallow population breeds here.
The Great Lakes Region
The marshy areas surrounding the Great Lakes in Minnesota, Wisconsin, Michigan, Ontario, and Ohio support millions of breeding tree swallows.
Coastal Alaska
The wet tundra habitat along Alaska’s coastline provides prime breeding grounds for tree swallows that migrate here each summer.
Population Declines
While still common, tree swallow populations have declined in some portions of their range over the past several decades. Habitat loss is one of the major threats. For example, coastal development has reduced nesting sites along the U.S. Atlantic coast. Wetland drainage for agriculture has also destroyed nesting habitat in certain areas.
Climate change may also negatively impact tree swallows. Drought and dry conditions reduce insect food sources. Extreme weather can flood nests and kill offspring. Unusually warm winters force some birds to expend more energy flying further south.
Providing more nest boxes in suitable habitat can boost local breeding populations. Protecting wetlands and limiting coastal development are also important conservation measures.
Range Maps
These maps from the Cornell Lab of Ornithology illustrate the breeding, wintering, and year-round ranges of tree swallows across North America:
Breeding Range
Wintering Range
Year-Round Range
Conclusion
In summary, tree swallows are most widespread and abundant across Canada, the northern U.S., and south along both coastlines into Central America and the Caribbean. They thrive in open wetland habitats that provide ample food resources and nesting sites. Marshes, lakes, rivers, coastal areas, and fields are all prime tree swallow habitat. Some key population centers include the Prairie Pothole Region, Great Lakes, and coastal Alaska. While still common, habitat loss has reduced numbers in certain areas. Protecting remaining wetlands and nest sites will be key to ensuring thriving tree swallow populations across their range into the future.