NATURAL HISTORY PROGRAMS
|BRINGING BACK THE BLUEBIRDS|
|Eastern Bluebird (Sialia sialas)
"The bluebird carries the sky on his back" Henry David Thoreau
The eastern bluebird is a member of the thrush family, which also includes other skilled songsters, such as the American robin and the wood thrush. Bluebirds are smaller than robins, being about seven inches in length. Males are a beautiful bright blue, with a rusty red on the upper breast reaching over the shoulders. The belly is bright white. Females are similar, but duller than males and are grayer in appearance. Juvenile birds have a speckled breast, and are grayish with a hint of blue in their wing and tail feathers. Females and juveniles also have a faint white eye ring.
Both male and female bluebirds sing, although the male is heard more frequently. The song is a rich sounding warble, heard in spring and summer, chur churlee-churlee. A sound that is heard year round, chur-lee?, is a location call to keep small flocks and families of bluebirds together. When agitated, bluebirds make a scolding chew call, sometimes in succession, sounding like a chatter.
In the mid to late 1800s two fierce competitors arrived on the scene. English sparrows and European starlings are both non-native species that were released into the wild and now range from coast to coast. These two species are both cavity nesters, and compete with native birds for nest sites. Sparrows have been observed at the Sanctuary building nests on top of active bluebird nests, and have killed both adult and nestling birds. Starlings quickly consume any wild foods that may have been utilized by wintering bluebirds.
By 1850, farms in New England were being abandoned and pastures began to revert back to woodlands. Habitat available for bluebirds was in decline. Combined with the starlings and sparrows, the use of harmful pesticides and increased human population, bluebirds were in trouble.
With a beautiful song and stunning color, the eastern bluebird is a favorite of birders and non-birders alike. Many people across its range have erected nest boxes for this species. Here at the Norcross Wildlife Sanctuary, we have hundreds of schoolchildren visit each winter to construct his or her own nestbox and learn about the plight of the eastern bluebird. Over the years, thousands nestboxes have been given to neighbors in hopes of providing a safe place for bluebirds to nest. We also monitor and maintain a bluebird trail of 42 boxes. For this past seasons results, click here.
Habitat & Food
Bluebirds, like most species, are creatures of habitat. Open lands, such as fields with
scattered trees, are the best places to observe bluebirds. They hunt the grasses for
insects, often times the bird will swoop down from a perch for crickets, caterpillars,
grasshoppers and other invertebrates. During the fall and winter when insects are not
available, fruits and berries are a major part of their diet (see below under Fall
Spring & Summer
Nestboxes should be ready for bluebirds when they begin to establish a territory in mid to late March. A male bluebird will often fly from perch to perch, singing, and visit potential nest sites within the territory. At times, males will hover in front of these nesting places, or land and poke their head in. Males do not necessarily arrive before the females; on some occasions the pair arrives to establish a territory together.
Here at Tupper Hill, we have observed male bluebirds land on top of a nestbox, sing and wave a wing. This wing-wave attracts the attention of the female, who then lands at the entrance to the box, and goes in to investigate. The pair may go through this numerous times until a site meets her approval.
As courtship ensues, a pair will be seen together around a selected nesting site more often. The male will bring food to the female, and the two will sing and wave wings to each other. At the Sanctuary, the first nests are usually found during the second week of April. Although both males and females have been observed carrying nesting material, the female does most of the actual construction.
Bluebird nests at Tupper Hill are built primarily of needles from white pine,
occasionally grasses are weaved in and, rarely, the entire nest is built of grasses. The
sturdy nests are carefully constructed within the nestboxes along the bluebird trail, and
have a deep cup in the center. None of the nests observed here have been lined, although
it is reported in literature that some bluebirds will line the cup with fine grasses,
feathers, or horsehair
It takes about a week to build the nest, and it is usually another week before the egg laying ensues. Here at the Sanctuary, the first eggs are seen in late April. Eggs are laid one a day, until the clutch is complete with four or five eggs. Most of the eggs observed are blue, but occasionally, white eggs are found.
The female does most of the incubating; males are not able to do this, as they do not have a brood patch. Males have been observed entering the house with food for the female while she incubates the eggs. They spend the night inside of the boxes with the females, standing on the edge of the nest.
The females incubate the eggs for about two weeks, and then the eggs begin to hatch. Young bluebirds are blind and almost devoid of feathers, except for a sparse, gray down. Females continue to brood until the nestlings develop more feathers and can keep warm. At this point, males are observed going to and from the house, bringing food and carrying away eggshells and fecal sacs. When the nestlings have more feathers, the female will join the male and bring food to the young.
Within a week, their eyes open. Feathers develop very fast, appearing as pencil leads first on the wings and then on the tail. The nestbox becomes very crowded and noisy when the parents return with food. Two to three weeks after the eggs hatch, the young are ready to make their first flight.
As with most bird species, fledglings may not be successful on their first attempt at flying. They may spend one or more nights on the ground or a low perch, and even though they have left the nest the parents continue to feed them. Please do not interfere with nature at this point, keep cats, dogs and children away and within a day or so the fledging will be soaring the skies and learning to find its own food.
At Tupper Hill, we have found that bluebirds will lay one or two and rarely three broods in a season. Once the young have fledged, the houses are cleaned and it is not unusual to observe the pair building a new nest within a week.
Fall & Winter
In late August and September, Bluebirds molt. It is at this time the young of the year have a partial molt and loose their spots. They now will resemble adults.
Bluebirds typically show some seasonal movement in autumn, wintering in the southeastern US and into Central America. However, if food is plentiful they will stay in the area. Small flocks of wintering bluebirds are not an uncommon sight at The Norcross Wildlife Sanctuary. We have observed them feeding on native berry-producing shrubs such as winterberry, red cedar, black gum, and dogwood. We DO NOT recommend planting non-native species as food for birds! If you are interested in a list of native plants for attracting birds one is available at our visitor center.
What To Do With Your Nestbox
To attract bluebirds, select an open grassy area that has some trees nearby for perch sites. Areas with thick brush or shrubs will attract house wrens, a native songbird. Here at the Norcross Wildlife Sanctuary, we place our nestboxes in pairs to minimize competition from the native tree swallow. The two species will nest next to each other, but are very territorial and will not allow their own kind to nest near them. The two boxes should be between 10 to 15 feet apart. Additional box pairs should be 100 yards away, distance enough to accommodate territories established by nesting pairs.
The 1½" diameter hole in Norcross nestboxes is too small for starlings, but English sparrows nest in them readily. Where we have problems with sparrows, Slot boxes are erected. This style box does not prevent sparrows from nesting, but allows space for escape should a sparrow enter while another bird is inside.
Boxes should be 4 to 6 feet above the ground, and should face away from prevailing winds. Our boxes are mounted on steel poles with predator baffles. Although it is said that bluebirds prefer south facing entrances, we have found that our birds prefer boxes that are in an open sunny location, out of the wind. Do not put nestboxes in areas treated with pesticides or herbicides. Most of a bluebirds diet is made up of insects, and these poisons travel up the food chain.
Do not be afraid to check your nestbox regularly. Clean the boxes out in late February or early March, and monitor the box weekly during the nesting season. Brief inspections will not cause nest abandonment, and actually benefit bluebirds. Avoid disturbing the birds during inclement weather, or after the nestlings eyes are fully opened and they develop their flight feathers. This may cause the birds to leave the nest prematurely.
Occasionally, blowfly larvae are found the nest. These larvae can become parasitic on the nestlings. If you do find blowflies, carefully remove the nest and nestlings, and clean the box. The adult bluebirds will NOT abandon their nests if you touch them.
If a wasp nest is found, try to remove it but use caution. If there is a baffle on the pole, you may want to check to see if wasps are underneath. They wont harm the birds here, but the monitor may disturb them.
When you approach the house, always knock so the incubating mother can exit. Houses that are monitored regularly do well with a baffle present on the pole, as the human scent left behind will attract predators. If signs of predation appear, such as broken eggs or missing nestlings, you may want to check your baffle or consider relocating the house. Dead nestlings should be removed from the nest.
Once the fledglings are gone, remove the nest. If the box is in need of thorough cleaning, a mild (1:10) bleach/water solution can be used, otherwise just sweeping it out with a wire brush will do. Boxes should be well ventilated and have drainage holes. We do not recommend painting or staining the box. Rough-cut lumber is preferred, as it is easier for the birds to cling to the box. Perches should never be placed on a nest box.
Other species that have successfully nested along our bluebird trail include tree swallow, black-capped chickadee, white-breasted nuthatch and house wren. These native species are protected by law and should not be removed. We have also had red and flying squirrels raise young in the nextboxes.
Boxes placed near buildings will be attractive to English sparrows or starlings. These nests should be removed as often as they are found. Both of these species are introduced and are not protected.
Left unpainted to weather naturally. Made of native pine. No perch, they do not need
Birdhouse Installation: 3 to 5 feet off the ground with the opening facing east - southeast. Place houses in low-cut, grassy areas with scattered trees and bushes. Don't place near houses, in shade or on overgrown hedgerows.
Bluebird trail: Set birdhouses at least 100 yards
apart because the birds are highly territorial. Run the houses so they can be checked
easily, possibly near a road or trail.
Feeding: Marvel Meal (WINTERING
BLUEBIRDS) This gives the birds a helping hand.