Yes, wood thrushes are migratory birds that breed in eastern North America and winter in Central America. They undergo long migrations each spring and fall between their breeding and wintering grounds.
When do wood thrushes migrate?
Wood thrushes migrate north to their breeding grounds in eastern North America in April and May. Their spring migration reaches its peak from mid-April to early May. They start migrating south again in August and September to return to their wintering grounds in Central America and the Caribbean. Most wood thrushes have left their breeding range by late October.
Spring migration
During spring migration, most wood thrushes leave their wintering grounds in Central America and the Caribbean in April. They fly north following the eastern part of North America, traveling mainly during the night and resting and feeding during the day. The males tend to arrive in the breeding range first, followed by the females 1-2 weeks later.
Wood thrushes time their migration to coincide with the emergence of insects and ripe wild fruits that they eat. This ensures abundant food resources upon arrival at their breeding sites. The earliest arrivals reach the southern U.S. states like Florida, Georgia, and South Carolina in early April. They reach the northern parts of their range in the U.S. and Canada in early to mid-May.
Fall migration
In late summer and early fall, wood thrushes begin congregating in groups in preparation for their southward migration. They start leaving their breeding grounds as early as late July and early August, though most migrate later in August through September. They travel across the eastern U.S. along the Gulf Coast to reach their Central American wintering grounds by late October. Their migration peaks in September.
Young birds born that spring migrate south later, from late August through October. The timing helps ensure abundant food resources along the migration route for these inexperienced birds.
Where do wood thrushes migrate?
Wood thrushes breed in deciduous and mixed forests across eastern North America. Their breeding range extends from southern Manitoba east to southern Quebec and the Canadian Maritime provinces. It reaches south throughout the eastern U.S. as far as northeastern Texas and northern Florida.
They winter primarily in southern Mexico, Guatemala, Belize, Honduras, Nicaragua, Costa Rica, and Panama. Some winter as far south as northern Colombia.
Breeding range
Within their breeding range, wood thrushes favor mature, deciduous forests with a dense understory. They are often found in moist, shady ravines and valleys with streams. Favorite nesting spots include forest openings, edges, and trails. They breed in both rural woodlands and parks within cities.
Wintering range
On their wintering grounds in Central America, wood thrushes inhabit tropical rainforests, forest edges, second growth, parks, and gardens from sea level up to 1,500 m elevation. They tend to occupy drier, more open habitats in winter than their breeding range.
How far do wood thrushes migrate?
Wood thrushes undertake incredibly long migrations each spring and fall. The total migration distance ranges from 1,800 – 4,800 km between their breeding and wintering grounds. That’s equivalent to a round trip from New York City to Denver, Colorado.
Some key examples of migration distances include:
- Birds breeding in Manitoba, Canada migrate about 4,000 km between their wintering grounds in Costa Rica.
- Birds from Quebec, Canada travel around 3,500 km each way to Panama.
- Wood thrushes breeding in Wisconsin migrate approximately 2,600 km south to Honduras and Nicaragua for the winter.
- Birds from Virginia fly some 1,800 km down to the Yucatan Peninsula in Mexico in the fall.
These marathon migrations are all the more impressive considering the wood thrush’s small size. They weigh just 30-50 grams, similar to a robin.
What routes do wood thrushes take?
Wood thrushes follow looping migration pathways each spring and fall as they travel between their breeding and wintering grounds. In general, they migrate southbound in the fall following coastal routes across the eastern U.S. In spring, they take more direct, inland routes back north.
Fall migration route
In fall, most wood thrushes migrate south following the Atlantic Flyway along the Atlantic coast. Others follow the Mississippi Flyway down the Mississippi River corridor. Their migration goes down the eastern U.S from New England and the Canadian Maritimes, through the Middle Atlantic states, Carolinas, Georgia and Florida.
Some eastern populations migrate southwest over land down through Texas and Mexico to Central America. Other groups fly directly southeast over the western Atlantic Ocean to the Caribbean and Central America.
Spring migration route
On northbound spring migration, wood thrushes generally take a shorter, more direct path than the coastal fall route. Many fly northwest over land from Central America back through Texas and the interior U.S., reaching the Great Lakes and southern Canada.
Birds wintering further east in the Caribbean also trace a direct path northwest back to the eastern U.S. and southern Canada. This straight route crosses the Gulf of Mexico, an impressive non-stop flight of up to 1,100 km lasting 15-24 hours.
Why do wood thrushes migrate?
Wood thrushes migrate primarily to find favorable habitats and abundant food as the seasons change. By moving south in fall, they escape declining food, plummeting temperatures, and snow cover in their northern breeding range. Their migration allows them to spend winters in tropical forests rich in fruit and insects.
In spring, they migrate north again to take advantage of the surge in insects, fruits, and nesting habitat opening up on their breeding grounds. Migration enables wood thrushes to breed in highly productive northern forests in summer, then switch to tropical forests in winter.
Declining food in fall
Wood thrushes time their fall migration to leave just as food becomes scarce on their breeding grounds. Caterpillars, beetles, and other insects decline as cold weather sets in. Wild fruits produced by shrubs and vines also dwindle after the late summer fruiting peak.
By migrating in August-October, they escape this seasonal decline in food. Their departure coincides with the onset of ripe fruits further south, ensuring a continuous food supply.
Favorable weather in winter
Migrating south allows wood thrushes to spend the winter in tropical and subtropical habitats. This warm, frost-free climate provides ideal overwintering conditions. Abundant fruit and insects allow the birds to easily meet their high energy needs.
In contrast, freezing temperatures and snow cover would make winter survival extremely difficult in their northern breeding range. Lack of food would prove fatal in the harsh northern winters.
Breeding habitat in spring
In spring, wood thrushes migrate north just in time to take advantage of newly emerging food resources. Trees and shrubs leaf out and produce nutritious fruits. Caterpillars and other insects vital for raising nestlings become abundant.
This synchronized arrival in northern forests allows wood thrushes to breed at the peak of seasonal food availability. Earlier arrival while trees are still leafless would limit nesting success.
Threats faced during migration
Wood thrushes face many threats and challenges during their long migratory journeys each spring and fall. These include:
- Habitat loss: Deforestation along migration routes, especially in Central America, reduces crucial stopover habitat for refueling.
- Severe weather: Storms, high winds, and precipitation can cause exhaustion or blow birds off course.
- Predation: Hawks, falcons, and other predators take their toll, especially on young, inexperienced migrants.
- Collisions: Windows, towers, and other structures claim many wood thrushes during migration.
- Light pollution: Artificial night lighting disorients migrants traveling after dark.
These threats contribute to ongoing declines in wood thrush populations across their range.
How do wood thrushes navigate migration?
Wood thrushes rely on a suite of amazing abilities to accomplish their marathon migrations each year. These include:
Innate guidance
Wood thrushes have inherited genetic programming guiding their migratory movements. Even young birds on their first migration know in what direction to travel without learning from older birds.
Compass senses
Wood thrushes likely use a combination of compass senses to orient themselves during migration. These may include:
- A sun compass based on the sun’s position to orient east-west
- A star compass using stars like Polaris to orient north-south
- An inner magnetic compass to detect Earth’s magnetic field
Landmark navigation
Wood thrushes also recognize and follow major landscape features during migration. These visual landmarks include coastlines, rivers, mountains, valleys, and vegetative transitions. Landmarks guide wood thrushes along learned migration routes.
Stopover site memory
Wood thrushes have excellent spatial memories and often stopover at the same sites year after year. They likely memorize key food sources along migration routes to relocate on future journeys.
Conclusion
In summary, wood thrushes are champion migrants that complete incredible seasonal journeys spanning thousands of kilometers. Their migrations take them between breeding habitats in northern forests and tropical wintering grounds. This seasonal movement allows wood thrushes to take advantage of optimal habitats and food resources as conditions change across North America. Their amazing navigation abilities enable wood thrushes to locate their migratory destinations and return to the same sites year after year. Despite facing many threats along the way, these marathon migrations are a key survival strategy allowing wood thrushes to thrive across a vast range.
