Coveside Bird House Features

Eastern Bluebird
Eastern Bluebirds are sexually dimorphic; that is, males and females look quite different. Males have bright blue heads, tails, backs, and wings. The sides, flanks, and throat are chestnut red.The underparts are also chestnut red from the chin down to the belly, but the belly is white.

Although there is much variation in their plumage, females are generally less colorful than males. They have light gray-blue heads, dull brown backs, and blue tails and wings. There is a slight white ring around the eye. In winter, the female's upper breast turns a pale reddish-brown.

Eastern Bluebirds can be found east of the Rockies, throughout the eastern United States and Canada, and down to central Mexico. Some populations are year-round residents, but others migrate to more southerly latitudes for the winter. Eastern Bluebirds are found in suburban and rural habitats containing sparse vegetation and scattered trees or other perches. They typically nest in fields, meadows, and orchards, avoiding both densely wooded and congested residential areas. Eastern Bluebirds prefer open sunny habitats, such as meadows, farm fields, lawns, and pastures, with short vegetation.

Eastern Bluebird Range Map
Eastern Bluebirds eat a variety of invertebrates, including caterpillars, butterflies, moths, grasshoppers, katydids, and spiders. They also feed on wild fruits. Primarily ground feeders, they prefer feeding and nesting in areas with short, sparse vegetation, which affords a clear view of ground-dwelling insects.

Eastern Bluebirds are monogamous. Pairs generally stay together throughout the breeding season, and pairs may breed together for more than one season. Some birds, however, may switch mates during a breeding season to raise a second brood. Both sexes defend territories; however, the males tend to defend territory edges while the females primarily defend the nest site.

The breeding season begins anytime from mid-March to early April. The male initiates selecting the nest site by "showing" the female several possible sites. The female may begin to build nests in several sites, but eventually she decides on a site and concentrates her efforts there. It usually takes four to six days to build the nest, but this varies with the time of season, weather, and the age and experience of the breeding pair. The nests, which are built in woodpecker holes, dead or rotting trees, and in nest boxes, are composed mainly of dry grasses, rootlets, and weed stems. Some nests are built entirely of pine needles. The cup is usually lined with fine grasses, rarely with hair and fur. Males may carry nest material to the nest, but they do not participate in the actual building of the nest. Rather, they spend much time guarding their mates during this time to prevent them from mating with other males.

Eggs can be laid as early as late March or as late as early June, depending upon the weather and latitude. Females may begin to lay eggs one or two days after the nest is completed, but some females wait a week or more. One egg is laid each day, in the morning. The average clutch has three to five eggs but as many as seven have been reported. Clutch sizes tend to be smaller for younger females and for second broods of the breeding season. The eggs are smooth and glossy and are sky blue or white in color. Because all eggs laid by a single female are the same color, the presence of an odd-colored egg in a clutch may indicate that another female has laid her egg in the nest, a practice known as egg dumping.

Eggs can remain un-incubated for awhile and still be viable; however, once incubation begins, it must be continuous. Females generally begin to incubate the day the last egg is laid. The incubation period is 12 to 14 days but can be longer in the case of extreme or prolonged cold weather.

Nestlings hatch within one or two days of each other, and the female broods the nestlings for a few days. Both adults tend the young. The nestlings begin to thermoregulate, or regulate their own body temperatures, when they are about six days old, and females then decrease the amount of time they spend brooding. Nevertheless, the females may continue to brood at night during cold weather. The young leave the nest after 16 to 22 days, but they remain dependent upon their parents for food and protection for three to four weeks.

Eastern Bluebirds raise two broods per season. Pairs may build their second nests on top of the first nest, or they may nest in an entirely new site. The male continues to tend the fledged young while the female begins to re-nest. Young from the first brood will reportedly help raise siblings from the second brood.

Families flock together until fall, when they merge with other family flocks. Some, but not all, bluebirds residing in the northern portions of the range migrate to southern latitudes, but those residing in southern latitudes tend to be residential. Adults tend to return to the same breeding territory year after year, but only a small percentage (three to five percent) of young birds return to their natal area to breed.

Mountain Bluebird
Unlike other bluebird species, male Mountain Bluebirds have no chestnut red on their bodies. The head, back, wings, and tail are a bright sky blue. Males are light blue from the chin to the belly, and grayish-white on the belly and undertail coverts.

Females have brownish gray upperparts. The wings, rump, and tail are a pale or light blue. Females sometimes have a pale reddish throat and breast, but more commonly, the throat and breast are gray brown.

Juveniles look like adult females, but they are darker and less colorful. Their breasts and sides are streaked with brown.

Mountain Bluebirds are found in the western parts of Canada and the United States. They are found at elevations above 5,000 feet, and they nest in open areas such as meadows, hayfields, grain fields, savannas, prairies, clear cuts, and the edges of coniferous and deciduous forests.

Mountain Bluebird Range Map
Mountain Bluebirds feed on a variety of insects, including beetles, weevils, ants, wasps, cicadas, flies, grasshoppers, katydids, and crickets. Unlike their eastern or western relatives, Mountain Bluebirds rarely eat seeds or berries. Mountain Bluebirds also differ from other bluebirds in that they often hover while foraging.

Males return to the breeding grounds before the females and establish territories. This happens in late March in the south but not until early April in the north. Females arrive several days to a few weeks later. Initially, pairs aggressively defend a large area around their nest site, but as the breeding season progresses, the size of the defended area decreases and becomes more localized around the nest. Mountain Bluebirds defend territories against others of their own species, or conspecifics, as well as against other bluebird species in areas where their breeding ranges overlap.

Mountain Bluebirds are basically monogamous. But, as with other bluebirds, both males and females sneak copulations with individuals that are not their mates. For this reason, males guard their mates, from the time a pair forms until the female lays her eggs. Pairs typically stay together throughout the season; however, individuals that have had an unsuccessful first nesting attempt may find a new mate for the rest of the breeding season. Some pairs mate for more than one breeding season. As in many species, the fact that many pairs mate with each other year after year probably reflects a male and female fidelity to a particular breeding site rather than to one another.

Mountain Bluebirds are solitary nesters, but pairs may nest in close proximity to others, depending on nest site availability. The beginning of the breeding season varies with latitude; birds in the southern portion of the range begin in early April, birds in northern latitudes begin in late May. The female chooses a nest site, which can be any natural cavity, abandoned woodpecker hole, cliff crevice, or nest box. Like other bluebirds, Mountain Bluebirds compete with House Sparrows and European Starlings for nest sites.

Only the female builds the nest, and it takes her anywhere from a few days to over a week to complete. Working most diligently in the morning, she constructs the nest of grass, weed stems, pine needles, twigs, rootlets, bark, and, sometimes, wool, hair, or feathers. Males are very attentive to their females during the nest-building period and spend most of their energy guarding their mates. Occasionally, they carry nest material to the cavity, but they are not known to actually weave it into the nest.

The first eggs are laid between late April and early May. Females lay one egg per day until the clutch is complete. The average clutch size is five to six eggs, but there can be as few as four or as many as eight. The eggs are smooth, glossy, unmarked, and are pale blue, bluish-white, or, rarely, white. Because all eggs laid by a female are the same color, any odd-colored eggs in a clutch indicates that another female has laid an egg in that nest, a behavior known as egg dumping.

While some sources report that both sexes incubate, incubation is mainly done by the female. Incubation begins when the next-to-last or the last egg is laid and lasts 13 to 14 days. Males often feed their mates during this period, and they continue to do so after the eggs hatch.

The female broods the nestlings for about a week after they hatch. The male does most of the feeding during that time. When the female ceases her daytime brooding and begins to brood only at night, both sexes start feeding the young equally. The nestlings fledge after 17 to 22 days. Initially, they are sedentary and depend heavily upon their parents for food and protection; however, as they mature, they begin to follow the parents around and actively solicit feedings. The male continues to care for the fledged young when the female begins to re-nest. After three to four weeks, the young are independent.

If a nesting attempt fails, Mountain Bluebirds will renest. They usually raise two broods in a breeding season. The fledged young may assist their parents in raising the next brood, but this behavior is considered rare.

Mountain Bluebirds reuse old nest sites both within a breeding season and in successive breeding seasons. Pairs that successfully raise a brood in a nest box may become faithful to that particular type of nest box. First-year breeding birds tend to nest in boxes identical to their natal box.

Families form flocks in late summer and merge with other family flocks as the season progresses. Juveniles that fledged early in the season and adults that bred unsuccessfully during the summer also join these flocks. It has not been determined whether the birds stay together in these flocks throughout migration or on their wintering grounds.

Mountain Bluebirds are the most migratory of the three bluebird species. Birds in the northern portion of the range begin to migrate sooner than those living in the southern portion. Mountain Bluebirds migrate to the southern United States and central Mexico, where they inhabit open lowlands, deserts, plains, and grasslands.

Western Bluebird
Western Bluebirds are similar in appearance to Eastern Bluebirds. The western species can be distinguished from its eastern relative by the sky blue color of the chin, throat, wings, and tail. Western Bluebirds also have chestnut-red breasts, flanks, and shoulders. In some birds, the back is partially or entirely blue. The belly and undertail coverts are blue gray.

Female Western Bluebirds are less colorful than males. They have a brownish gray head and back, light blue wings and tail, and grayish white throat, belly, and undertail coverts. The breast is a pale rust. The females also have a dull white eye ring.

Western Bluebirds can be found in the Southwest and all along the West Coast of the United States. This species is generally residential but moves to lower elevations for the winter months. Western Bluebirds breed in open habitats with scattered trees, such as farmland, orchards, and the edges of open coniferous and deciduous forests.

Western Bluebird Range Map
Western Bluebirds feast on a variety of invertebrates, including caterpillars, grasshoppers, beetles, ants, and snails. In winter, their diet includes wild berries.

The breeding biology of the Western Bluebird is similar to that of the Eastern Bluebird. Their breeding season can begin anytime from early April to early May. Females build their nests in the natural cavities of snags or rotting trees, in woodpecker holes, or in nest boxes. These nests can be anywhere from 4 to 40 feet above the ground. The nest is a loose collection of grasses, weed stems, and, sometimes, hair and feathers.

Females usually lay four to six eggs in a clutch, but clutches can range from three to eight eggs. The unmarked eggs are pale blue, bluish-white, or white in color.

Only the female incubates the eggs, for a period of 13 to 14 days.

Both adults tend the young, feeding them mostly soft-bodied insects. After 19 to 22 days, the young fledge, but they don't reach full independence for three to four weeks. The male may continue to care for the young by himself while the female begins to renest.

This species is believed to raise two broods per breeding season.

Like Eastern Bluebirds, some populations of Western Bluebirds migrate to southern latitudes for the winter months, while other populations are residential. Nevertheless, even residential individuals move to lower elevations in winter.