Photo: Rick & Nora Bowers/Vireo

Western Bluebird

Sialia mexicana

In partly open terrain of the west, from valley farms and orchards to clearings in mountain pine forest, this bluebird is often common. In summer it is often seen perching alone on fence wires by open meadows, fluttering down to pluck insects from the grass. In winter, small flocks of Western Bluebirds are often heard flying overhead or seen feeding on berries in trees. Sometimes, as when juniper woods have heavy berry crops, the bluebirds may gather by the hundreds.
Conservation status In recent decades, numbers have declined over much of range. Provision of birdhouses probably has not kept pace with loss of natural nest sites.
Family Thrushes
Habitat Scattered trees, open conifer forests, farms; in winter, semi-open terrain, brush, deserts. Breeds in semi-open areas including pine woods, oak woods, streamside groves, ranch country, sometimes in pinyon-juniper woods, but avoiding hot dry regions. Winters in many kinds of open or semi-open habitats, especially in pinyon-juniper, also in desert, farmland, others.
In partly open terrain of the west, from valley farms and orchards to clearings in mountain pine forest, this bluebird is often common. In summer it is often seen perching alone on fence wires by open meadows, fluttering down to pluck insects from the grass. In winter, small flocks of Western Bluebirds are often heard flying overhead or seen feeding on berries in trees. Sometimes, as when juniper woods have heavy berry crops, the bluebirds may gather by the hundreds.
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Feeding Behavior

Often forages by perching fairly low and flying down to ground to capture insects, sometimes hovering briefly before pouncing. May catch insects in mid-air, or may seek them among foliage. Perches or flutters among branches to take berries.


Eggs

4-6, sometimes 3-8. Pale blue, unmarked; occasionally white. Incubation is by female, incubation period not well known. Young: Both parents bring food to nestlings. Age of young at first flight is not well known, probably between 2 and 3 weeks. Probably 2 broods per year.


Young

Both parents bring food to nestlings. Age of young at first flight is not well known, probably between 2 and 3 weeks. Probably 2 broods per year.

Diet

Mostly insects and berries. Insects make up majority of diet, especially in summer; feeds heavily on grasshoppers, caterpillars, beetles, ants, also many other insects. Berries and small fruits are important in diet especially in winter; among those eaten are fruits of mistletoe, juniper, and elderberry.


Nesting

Male typically arrives on breeding grounds before female, and defends nesting territory by singing. In courtship, male may flutter in front of female with wings and tail partly spread, while singing. Male may also feed female. Nest site is in cavity, such as natural hollow in oak or pine, old woodpecker hole, birdhouse, sometimes hole in building. Usually nests fairly low, rarely up to 50' above the ground. Nest in cavity is probably built mostly by female, but male may take part. Nest is a rather loose cup of twigs and weeds, lined with finer grass.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Permanent resident in some southern areas; migratory in the north, arriving rather early in spring and lingering late in fall. Winter range varies from year to year depending on food supplies.

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Migration

Permanent resident in some southern areas; migratory in the north, arriving rather early in spring and lingering late in fall. Winter range varies from year to year depending on food supplies.

  • All Seasons - Common
  • All Seasons - Uncommon
  • Breeding - Common
  • Breeding - Uncommon
  • Winter - Common
  • Winter - Uncommon
  • Migration - Common
  • Migration - Uncommon
Songs and Calls
Soft calls sound like phew and chuck. Song is a short, subdued cheer, cheer-lee, churr.
Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How Climate Change Will Reshape the Range of the Western Bluebird

Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.

Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.

Climate threats facing the Western Bluebird

Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.

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