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Overview and Description
The Eastern Bluebird, Sialia sialis, is a medium-sized thrush found in open woodlands, farmlands and orchards.
Adults have a white belly. Adult males are bright blue on top and have a red throat and breast. Adult females have duller blue wings and tail, a brownish throat and breast and a grey crown and back. Eastern Bluebirds are found in the Eastern US as the name implies.
Breeding
Eastern Bluebirds typically have two broods in the northern portions of their range while it is common for them to have three broods in the southern part of their range. In the case of a warm summer that lasts later than usual, three broods can be expected even in the Northeastern United States. The number of broods is mainly dependent on the weather and adequate availability of food (insects).
Eastern Bluebirds are cavity nesters and build a tall nest made mainly from grasses. The female lays two to seven bluish eggs that are incubated primarily by her. The eggs hatch in 12 to 14 days. The hatchlings are fed by both parents and the young ones fledge in another 14 to 20 days. Blowfly larvae are commonly found in bluebird nests but it is rare for the infestation to cause death of the hatchlings (by blood loss).
Conservation Status
The population of the Eastern Bluebird declined seriously enough in the past century to reach critical status by the mid-1900s. The decline was due to:
- Habitat destruction (loss of fields and nesting cavities in split-rail fences)
- Pesticide use
- Nest predation by House Sparrows and European Starlings; both of which are non-native species introduced by humans
Fortunately, the species was rescued by a network of birding enthusiasts who erected nesting boxes for Bluebirds, with close monitoring necessary to prevent House Sparrows from nesting in them. They remain threatened, however, with competition still prevalent from other species (for e.g. Tree Swallows, which are a native species and which also nest in cavities) and in certain states of the US they can still be difficult to spot. It is worth noting that due to the increase in their numbers in the past few decades, they are not protected under the CITES or U.S. Endangered Species Act.
The Bluebird is the state bird of Missouri and New York.
The Eastern Bluebird is also native to Bermuda, although the birds found there may constitute a sub-species. In Bermuda, the Bluebird is also endangered due to the loss of 8 million Bermuda cedar trees in the 1940s, and nest predation by introduced Sparrows, Starlings and Kiskadees (especially the last, which was introduced to Bermuda in 1957, and has also contributed to the declines of other species like the Cardinal, and the Catbird). Similar methods to those used in the USA have been adopted in Bermuda to sustain the Bluebird. These efforts have had limited success, however, balanced against the rapid increase of the human population over the last half-century. Much of Bermuda's population had historically been centred in two urban areas, but has sprawled over Bermuda's land mass since the 1948 legalisation of motor vehicles. Hurricane Emily, in 1987, destroyed much of the remaining forestation, with severe effects on many bird species, including the Bluebird.
References
- Database entry includes justification for why this species is of least concern
External Links
- Life Histories of Familiar North American Birds: Eastern Bluebird.
- Bermuda Audubon Society.
- Bermuda Online: Bermudian Fauna.
- Bermuda Aquarium, Museum & Zoo Biodiversity Project.
- Bird Life International: Eastern Bluebird - Species Factsheet.
- Bangs and Bradlee, Birds of Bermuda (Pdf).
Bluebirds | United States state birds | Natural history of Bermuda
"Eastern Bluebird"