Western bluebirds are a familiar sight in the western United States during the spring and summer months. But when winter arrives, these colorful songbirds fly south to escape the cold weather. So where exactly do western bluebirds go when it’s time to migrate for the winter?
Western Bluebirds Migrate to the Southern United States and Mexico
The majority of western bluebirds that breed in the western United States migrate south to spend their winters in the southern parts of the country or in Mexico. Their winter range extends from southern California and Arizona across New Mexico and Texas and into northern Mexico.
Western bluebirds tend to follow mountain ranges during migration. This allows them to stop and refuel in areas with adequate food and cover. They migrate through mountain passes and along forested corridors in search of familiar environments.
Arizona and New Mexico are Key Wintering Areas
Many western bluebirds spend their winters in Arizona and New Mexico. The milder climates, open woodlands, and grasslands in these states provide ideal overwintering habitat.
In Arizona, western bluebirds congregate in areas such as the Santa Rita and Chiricahua Mountains in southern Arizona. They are also found in desert grasslands and oak woodlands around Phoenix and Tucson.
New Mexico offers extensive piñon-juniper forests and open ranchlands that attract wintering bluebirds. The Gila National Forest and foothills of the Sangre de Cristo Mountains host sizable winter populations.
California’s Central Valley Sees Large Numbers
California’s Central Valley serves as an important winter home for western bluebirds that breed further north. Bluebirds can be found there from November to February, frequenting hedgerows, orchards, and open agricultural fields.
The southern San Joaquin Valley sees some of the largest concentrations of overwintering bluebirds in California. Kern and Tulare Counties likely host tens of thousands of western bluebirds in midwinter.
Texas Offers Suitable Winter Habitat
Western bluebirds also overwinter in decent numbers across central and eastern Texas. They use open pasturelands, scattered trees and shrubs, suburban yards, and parks.
Texas’ Edwards Plateau and Blackland Prairie regions provide excellent winter habitat for bluebirds. Some migrate as far as the Lower Rio Grande Valley along the Texas-Mexico border.
Western Bluebirds Use Similar Habitats in Winter
Although western bluebirds migrate south for winter, they select habitats that are similar to those used in summer. Their winter habitats generally consist of open country interspersed with trees and shrubs.
Bluebirds perch on fences or trees to scan for insects. Access to berry crops and seeds from grasslands and meadows provide important food sources to supplement their insectivorous diets.
Pastures, agricultural areas, mountain meadows, desert grasslands, open woodlands, savannahs, parks, and even some suburban neighborhoods provide the combination of open ground, scattered trees, and food resources preferred by wintering western bluebirds.
They Often Form Loose Winter Flocks
Western bluebirds are territorial and solitary nesters. But when not breeding, they often gather in loose flocks of a dozen or more individuals. These flocks forage together and roost communally in cavities or thick vegetation.
Winter flocks help bluebirds locate food resources and likely provide protection from predators. The extra sets of eyes make it easier to watch for predators like hawks and falcons.
migrating and wintering bluebirds face threats
Bluebirds face a number of threats during migration and winter:
- Loss of habitat along migration routes and in wintering areas reduces food resources and safe roosting spots.
- Use of pesticides reduces insect prey availability.
- Severe weather such as ice storms can cause direct mortality and reduce insect populations.
- Collisions with vehicles and windows are a significant source of mortality.
Despite these threats, western bluebird populations remain relatively stable. Ongoing conservation efforts focused on maintaining open habitat with nesting cavities are key to sustaining bluebird populations.
They Start Heading North Again in February and March
Western bluebirds typically begin leaving their wintering grounds in February and March. Their northern migration peaks in April as they hurry to reach breeding areas and claim nesting cavities.
Early nesting is important so that bluebirds can raise multiple broods during the spring and summer. The males arrive first on the breeding grounds to select and defend nesting cavities.
Breeding Range Closely Matches Summer Range
After returning north in spring, western bluebirds breed across much of the western United States. Their breeding range extends from coastal and interior California north through Oregon, Washington, and British Columbia.
It reaches east into Idaho, western Montana, Wyoming, Colorado, and New Mexico. Isolated breeding populations occur in western South Dakota, Nebraska, and Oklahoma as well.
This breeding range closely matches the summer range, with western bluebirds mostly vacating only the northernmost fringe of their breeding range in winter.
Conservation Measures Help Bluebird Populations
installation of nest boxes in appropriate habitat
planting of native food sources
provision of winter roost boxes
Using insecticides judiciously
Careful window placement in new constructions
With active management and habitat conservation, western bluebird populations should remain stable despite the threats posed by modern landscapes.
| Month | Western Bluebird Activity |
|---|---|
| January | Wintering in southwest |
| February | Some early migrants head north |
| March | Peak spring migration north |
| April | Arrival on breeding grounds |
| May | Nest building and egg laying |
| June-August | Raising multiple broods of young |
| September | Fall migration starts south |
| October | Peak fall migration south |
| November | Arrival on wintering grounds |
| December | Wintering in southwest |
Conclusion
In conclusion, western bluebirds migrate from their breeding range in the western United States to winter primarily in the southwestern U.S. and Mexico. Mild climates and open habitats in Arizona, New Mexico, Texas, and California’s Central Valley support the majority of wintering bluebirds.
Though they face threats like habitat loss and vehicle collisions, conservation measures focused on providing suitable breeding habitat and food resources continue to sustain western bluebird populations. Understanding their annual cycle helps inform management efforts for this iconic and beloved songbird.
