Western Bluebirds
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The Western Bluebird (Sialia mexicana) is a medium-sized thrush.
Description
Adults have a grey belly. Adult males are bright blue on top and on the throat with a red breast; they have a brown patch on their back.
Adult females have duller blue wings and tail, a brownish breast and a grey crown, throat and back.
Distribution / Range
Their breeding habitat is semi-open country across western North America, but not desert areas. Northern birds migrate to the southern parts of the range; southern birds are often permanent residents.
Diet / Feeding
These birds wait on a perch and fly down to catch insects, sometimes catching them in midair. They mainly eat insects and berries.
Nesting
They nest in cavities or in nest boxes, competing with Tree Swallows, House Sparrows, and European Starlings for natural nesting locations. Because of the high level of competition, House sparrows often attack western bluebirds for their nests. The attacks are made both in groups or alone.
Nest type and habitat comparison
In restored forests Western Bluebirds have a higher probability of successfully fledging young than in untreated forests, but they are at greater risk of parasitic infestations. The effects on post-fledging survival are unknown. Western Bluebirds have been found to enjoy more success with nest boxes than in natural cavities. They started egg laying earlier, had higher nesting success, lower predation rates, and fledged more young in boxes than in cavities but they did not have larger clutches of eggs.
The eggs are commonly 4-6 which average 20.8 x 16.2mm. Eggs are oval shape with a smooth and glossy shell. They are pale blue to bluish white and sometimes white in color. Nestlings remain in a nest about 19-22 days before fledging.
Rearing of young
According to genetic studies, 45% of Western Bluebirds' nests carried young that were not offspring of the male partner. In addition, western bluebirds will help their parents raise a new brood after their own nest fails. Western Bluebirds are also helped by other birds belonging to a different species altogether. Violet-green swallows have been seen feeding and defending the nests of Western Bluebirds.
Copyright: Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia.org)
Related Websites:
- Sound File - Source: Naturesongs.com
- Sound File - Source: Naturesongs.com
- USGS (Photos & Info)
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