Chimney swifts are aerial insectivores known for their distinctive flight and adaptation to human structures. Often called “flying cigars” due to their body shape and rapid wingbeats, they spend nearly their entire lives airborne, even eating, drinking, and bathing in flight. Unlike most birds, chimney swifts cannot perch on horizontal surfaces; instead, they cling vertically to rough textures like the inside of chimneys. While once nesting in hollow trees, they now commonly use chimneys for nesting and roosting, making them a familiar presence in urban and suburban areas.
The Annual Migration Schedule
Chimney swifts undertake an extensive annual migration, traveling thousands of miles between their North American breeding grounds and their South American wintering areas. Their departure from northern latitudes typically occurs from late summer into early fall, generally spanning August and September. However, the precise timing can vary based on geographic location, with those in more northern regions often leaving earlier. For example, swifts in the Southeast United States usually begin their southward journey in mid-October, while those in the Intermountain West may depart by mid-September.
The return migration to North America takes place in the spring, with birds arriving between March and May. Like their departure, spring arrival dates depend on the specific region. Southern states may see swifts as early as late March, while areas further north, such as New England, may not observe their return until late April or early May.
Why Chimney Swifts Migrate and Where They Go
The primary driving force behind the chimney swift’s long-distance migration is the availability of their insect food source. As temperatures cool in North America during the fall, flying insect populations decline, prompting the swifts to seek warmer climates where food remains abundant. This migratory behavior also allows them to escape freezing temperatures in their breeding range.
Their wintering grounds are primarily located in the Amazon basin of South America. Specifically, they spend the colder months in parts of Peru, Ecuador, Chile, and Brazil, with recent studies also confirming their presence as winter residents in Colombia. In these tropical regions, chimney swifts inhabit open country, savannas, wooded slopes, and humid forests. This habitat provides the continuous supply of airborne insects necessary for their survival throughout the non-breeding season.
Preparing for Departure and What Homeowners Should Know
As the breeding season concludes, chimney swifts begin to prepare for their long migratory flight. This often involves forming large communal roosts, where hundreds or thousands of birds gather in suitable chimneys each evening before continuing their journey south. This natural and important behavior is a part of their pre-migratory cycle, and homeowners may notice increased activity and chattering sounds around their chimneys during this time.
Homeowners should avoid disturbing chimney swifts during their nesting or roosting periods. These birds are protected under the Migratory Bird Treaty Act, making it illegal to remove or interfere with them, their nests, or their eggs while they are present. Wait until the swifts have naturally departed for the season before undertaking any chimney cleaning or capping projects. Once the swifts have left for their wintering grounds, typically by late fall, chimneys can be cleaned to remove any nesting debris. Installing a chimney cap after their departure can prevent swifts from entering in subsequent seasons, ensuring both homeowner convenience and the continued well-being of this migratory species.