The Brown Thrasher (Toxostoma rufum) is a songbird found throughout much of the eastern and central United States and southern Canada during the summer breeding season. However, as temperatures cool in autumn, most Brown Thrashers migrate south to spend the winter in the southern United States, Mexico, Central America, and the Caribbean.
Do Brown Thrashers migrate?
Yes, the majority of Brown Thrashers are migratory, breeding in northern areas in the summer and migrating south to warmer climates for the winter. However, some individuals, especially those living in the southernmost parts of their breeding range, are permanent residents who do not migrate.
Where do migrating Brown Thrashers spend the winter?
The winter range of the migratory Brown Thrasher spans across the southern United States from California east to Florida and south through Mexico, Central America, and the Caribbean islands. Some key wintering areas include:
- Southeastern United States from southern Virginia south to Florida and west to eastern Texas
- Southern California
- Southern Arizona
- Southern New Mexico
- Southern Texas
- Coastal areas of western Mexico
- Yucatan Peninsula
- Caribbean islands including the Bahamas, Cuba, Jamaica, and Puerto Rico
Within their winter range, Brown Thrashers occupy habitats including thickets, woodland edges, scrub, gardens, and agricultural areas. They often congregate in loose flocks while feeding.
When do Brown Thrashers migrate?
Most Brown Thrashers migrate south between September and November. The timing of migration depends on a few factors:
- Age – Adult birds tend to migrate earlier than juveniles
- Location – Birds that breed farther north migrate earlier than those that breed farther south
- Weather – The onset of cold weather with frost triggers migration movements
Return migration to the breeding grounds typically occurs between March and May. Adults often migrate back earlier than juveniles. Some individuals, especially adult males, return very early in spring to claim territories.
How do Brown Thrashers migrate?
Brown Thrashers make their lengthy migratory journeys by flying mostly at night. They rest and feed during the daytime. Some key facts about their migration strategy include:
- They fly solo, not in flocks like some migratory songbirds.
- They can cover hundreds of miles in a single night of migration.
- They stopover to rest and refuel along the way in thickets, woodlands, and scrub habitats.
- Younger birds making their first migration may become disoriented and end up off-course.
Why do Brown Thrashers migrate?
Brown Thrashers migrate primarily due to changes in food availability and weather between their breeding and wintering grounds. Some key factors driving their migration include:
- Lack of insects – As cold weather sets in, the insects and other invertebrates thrashers feed on become scarce.
- Scarcity of fruit – The fruit that thrashers rely on also becomes less abundant as winter nears.
- Freezing temperatures – Brown thrashers struggle to survive freezing conditions far north during winter.
- Lack of cover – The loss of leaf cover in northern forests also leaves thrashers exposed.
By migrating south, Brown Thrashers can find more plentiful food supplies and milder weather conditions to survive the winter months.
Major stopover sites
On their migratory journeys between breeding and wintering grounds, Brown Thrashers stop over to rest and refuel. Some major stopover sites include:
- Southern Appalachian Mountains
- Coastal woodlands of the Carolinas
- Northern Gulf Coast including coastal Alabama and Louisiana
- Rio Grande Valley of southern Texas
- Southern Florida including the Everglades
These areas provide critical food resources to rebuild energy stores in the form of insects, fruit, and seeds before thrashers complete their migrations.
Threats faced during migration
Brown Thrashers face a number of natural threats during their annual migrations, including:
- Inclement weather – Storms, high winds, heavy rain can blow thrashers off course and lead to exhaustion or death.
- Lack of stopover habitat – Destruction of woodlands and thickets leaves fewer places to rest and refuel.
- Predators – Hawks, falcons, owls, and other predators take their toll, especially on younger birds.
- Collisions – Collisions with structures such as buildings and communication towers are an increasing risk.
Habitat loss across breeding and migratory routes poses a major long-term threat to migratory Brown Thrasher populations.
Conservation status
The Brown Thrasher has a large range and population, estimated at around 13 million birds. Overall numbers are declining but the rate of decline is relatively small. The species is not considered globally threatened and is classified as Least Concern on the IUCN Red List of Threatened Species.
However, Breeding Bird Survey data shows Brown Thrasher populations declined by around 2% per year from 1966 to 2015. Conservationists attribute this to threats on their breeding and wintering grounds, as well as habitat loss along migratory routes. Maintaining healthy ecosystems across their full range is important for the long-term conservation of Brown Thrashers.
Conclusion
In conclusion, most Brown Thrashers are migratory songbirds that breed across much of eastern and central North America in summer and migrate south to spend the winter in the southern U.S., Mexico, Central America, and the Caribbean. Driven by changing food supplies and freezing temperatures, they head south typically between September and November, traveling solo at night and stopping over to rest and refuel along the way. While not currently threatened, loss of habitats across their range poses a long-term risk. Protecting stopover sites and habitats across their full annual cycle will give Brown Thrashers the best chance at thriving.