Eastern Bluebird (Sialia sialis)
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The Eastern Bluebird, Sialia sialis, is a medium-sized thrush found in open woodlands, farmlands and orchards.
Eastern Bluebirds are found east of the Rockies, southern Canada to the Gulf States and southeastern Arizona to Nicaragua.
The Eastern Bluebird is the official State Bird of Missouri and New York, USA.
Description
Adults have a white belly.
Adult males are bright blue on top and have a reddish brown throat and breast. The bright blue breeding plumage of the male, easily observed on a wire or open perch, fluttering down to the mowed grass to capture a grasshopper, cricket or beetle makes this species a favorite of birders.
Adult females have duller blue wings and tail, a brownish throat and breast and a grey crown and back.
Calls / Vocalizations
The male's call includes sometimes soft warbles of jeew or chir-wi or the melodious song chiti WEEW wewidoo (Sibley, 2000).
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 millionBermuda 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 overBermuda's land mass since the 1948 legalisation of motor vehicles. Hurricane Emily, in 1987, destroyed much of theremaining forestation, with severe effects on many bird species, including the Bluebird.
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 secondary cavity nesters using an old woodpecker hole, natural cavity, hole in a rail fence or nesting box.
Mainly the female builds a cupped-shaped nest made from dried grasses or pine needles and lined with finer grasses. The female lays two to seven bluish (or rarely, white) 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 (avg. 18.8) 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).
Approximately two-thirds of the diet of an adult eastern bluebird consists of insects and other invertebrates. The remainder of the bird's diet is made up of wild fruits.
Favored insect foods include grasshoppers, crickets, katydids, and beetles. Other food items include earthworms, spiders, millipedes, centipedes, sow bugs, and snails.
Fruits are especially important when insects are scarce in the winter months. Some preferred winter food sources include dogwood, hawthorn, wild grape, and sumac and hackberry seeds. Supplemental fruits eaten include blackberries, bayberries, fruit of honeysuckle, Virginia creeper, Eastern Juniper, and pokeberries.
Bluebirds feed by perching on a high point, such as a branch or fence post, and swooping down to catch insects on or near the ground.
The availability of a winter food source will often determine whether or not a bird will migrate. If bluebirds do remain in a region for the winter, they will group and seek cover in heavy thickets, orchards, or other areas in which adequate food and cover resources are available.
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
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 thoughtful of conservation, however, with competition still prevalent from other species (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 CITES or U.S. Endangered Species Act.
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Eggs, Incubation and Fledging Times
| # Eggs | Incubation Time |
Time to fledge |
|
| Eastern Bluebird | 3-6 | 12-18 days | 16-21 days |
- Listen to an Eastern Bluebird Sing - Source: USGS Patuxent Wildlife Research Center
- Another Eastern Bluebird Song - Source: Florida Museum of Natural History
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