PENNSYLVANIA GAME COMMISSION
MIDDLE CREEK WILDLIFE MANAGEMENT AREA
EASTERN BLUEBIRD INFORMATION SHEET
Building and placing cavity nest boxes is an excellent way to assist the survival of cavity nesting birds and mammals. Wood Ducks and Eastern Bluebirds have made a comeback from near extinction because of these efforts.
When erecting homes for birds or other wildlife it is important to check the boxes when appropriate and annually clean them. Placing nest boxes signifies a commitment to wildlife. If this commitment does not include cleaning and maintenance, please do not erect any boxes.
Cavity nesting creatures have specific needs such as habitat, size of cavity, size of opening, height above the ground, etc. Know what each species requires so wildlife receives the maximum benefit.
EASTERN BLUEBIRDS
Appearance---Male Eastern Bluebirds are bright blue with a rusty-red colored throat and breast. Females are duller with a gray back and lighter colored breast. Young are speckled like robins.
Nest box requirements:
A 1.5 inch round hole, a floor 4"x4", 5"x5" or 4"x5.5" with an inside height of 8".
Placement of nest boxes:
Put at eye height (4 to 5 feet) on an iron post.
If erecting more than one box for Eastern Bluebirds they must be spaced at least 300 feet apart.
The best habitat for bluebirds is an open area with short grasses such as a field, pasture, lawn or similar area with a few scattered trees for perching.
Avoid brushy areas (Problem---House Wrens) and residential and farm buildings (Problem---House Sparrows)
Do not place a box for bluebirds near an area where pesticides are used. Bluebirds feed on insects from the ground and these poisons may kill the adults as well as their young.
EASTERN BLUEBIRD COMPETITORS
The best habitat for bluebirds is an open area with short grasses such as a field, pasture, lawn or similar area with a few scattered trees for perching.
Avoid brushy areas (Problem---House Wrens) and residential and farm buildings (Problem---House Sparrows)
Do not place a box for bluebirds near an area where pesticides are used. Bluebirds feed on insects from the ground and these poisons may kill the adults as well as their young.
EASTERN BLUEBIRD COMPETITORS
Tree Swallow: Males and females both have iridescent greenish-blue backs with pure white underneath. Juveniles are brown-backed with pure white underneath.
House Sparrow: Males have black "bibs" and bills with white cheeks. Females have an un-streaked dingy breast, bold buffy eye line, and a streaked back.
House Wren: Small brown-streaked birds with a finely barred, narrow, rounded tail that is usually cocked upward.
EASTERN BLUEBIRD vs. TREE SWALLOW ---
Should Eastern Bluebirds and Tree Swallows compete for the same box, follow these recommendations based on research conducted at Middle Creek Wildlife Management Area.
Place 2 boxes side-by-side 1 to 9 feet apart. Swallows will nest in only one box, while the other may be used by bluebirds or another species. Erecting boxes side-by-side at inter-box distances of more than 10 feet may result in swallows nesting in both boxes.
Place 2 boxes on the same post back-to-back. Bluebirds may nest in one side while swallows nest in the other. Occasionally, swallows will nest in both boxes.
NESTS
Eastern Bluebirds start building their nests in late March into early April. The nests are composed mostly of fine grasses woven into a well-defined cup. If pine needles are available the nest will be made of grass and pine needles. It may occasionally contain some feathers. The female bluebird takes from one to six days to build her nest. Bluebirds nest twice and, occasionally, three times during the nesting season.
Tree Swallows begin building their nests in late April into early May and may take up to two weeks to complete it before egg laying begins. The nests are composed of fine and coarse pieces of grass and a lot of feathers. At the beginning the swallow and bluebird nests look alike. The swallows add feathers to the nest and as it nears completion the feathers are arranged in an arc over the nest. They usually nest only once during the nesting season.
House Sparrow nests are trashy looking. They are composed of pieces of large grass, feathers, plastic, string and other litter, which usually completely fills the box. The sparrow arranges the items to form an arch-like effect over its nest.
House Wren nests are composed almost entirely of sticks with a small cup lined with hair. Male House Wrens often create "dummy" stick nests in every birdhouse in the area. These “dummy” nests may be removed. Nests with eggs should be left alone.
EGGS
Eastern Bluebirds and Tree Swallows lay one egg/day. The eggs are usually laid in
the morning. Bluebird eggs are usually blue, but one in 20 clutches contains white eggs.
Tree Swallow eggs are smaller than bluebird eggs and are pure white.
House Sparrow eggs are greenish-gray with dark splotches.
House Wren eggs are very small and are cream colored with dark brown splotches.
MONITORING---
Place 2 boxes side-by-side 1 to 9 feet apart. Swallows will nest in only one box, while the other may be used by bluebirds or another species. Erecting boxes side-by-side at inter-box distances of more than 10 feet may result in swallows nesting in both boxes.
Place 2 boxes on the same post back-to-back. Bluebirds may nest in one side while swallows nest in the other. Occasionally, swallows will nest in both boxes.
NESTS
Eastern Bluebirds start building their nests in late March into early April. The nests are composed mostly of fine grasses woven into a well-defined cup. If pine needles are available the nest will be made of grass and pine needles. It may occasionally contain some feathers. The female bluebird takes from one to six days to build her nest. Bluebirds nest twice and, occasionally, three times during the nesting season.
Tree Swallows begin building their nests in late April into early May and may take up to two weeks to complete it before egg laying begins. The nests are composed of fine and coarse pieces of grass and a lot of feathers. At the beginning the swallow and bluebird nests look alike. The swallows add feathers to the nest and as it nears completion the feathers are arranged in an arc over the nest. They usually nest only once during the nesting season.
House Sparrow nests are trashy looking. They are composed of pieces of large grass, feathers, plastic, string and other litter, which usually completely fills the box. The sparrow arranges the items to form an arch-like effect over its nest.
House Wren nests are composed almost entirely of sticks with a small cup lined with hair. Male House Wrens often create "dummy" stick nests in every birdhouse in the area. These “dummy” nests may be removed. Nests with eggs should be left alone.
Mouse nests are composed of grass, fur, plant material and litter often formed into a hollow ball. Mice should be discouraged from using bird boxes. A gallon metal can placed on the metal post below the nest box will prevent mice entry.
EGGS
Eastern Bluebirds and Tree Swallows lay one egg/day. The eggs are usually laid in
the morning. Bluebird eggs are usually blue, but one in 20 clutches contains white eggs.
Tree Swallow eggs are smaller than bluebird eggs and are pure white.
House Sparrow eggs are greenish-gray with dark splotches.
House Wren eggs are very small and are cream colored with dark brown splotches.
MONITORING---
When approaching a box make some noise so the birds are aware of human presence.
Open the box carefully and make observations as quickly as possible to avoid unnecessarily disturbing the birds. Keep a record of these observations.
Touching the nest, eggs, nestlings or adults will not cause the birds to abandon their nest.
At the end of the nesting season, (usually in mid-August) the nest boxes should be cleaned out. In late winter or early spring the houses should be checked again and any nesting material of mice, flying squirrels, etc. should be removed so the houses are ready by early March for new residents.
DOS AND DON'TS
Avoid walking on the grass directly from one box to the next--Raccoons may follow
human scent and find an easy meal.
Remove all House Sparrow nests and contents. Discard nesting material away from
the nest boxes.
Remove all mouse nests. They can find housing elsewhere. Avoid coming in contact
with either the mice or their nesting material.
PROBLEMS (Evidence and Suggestions)
Raccoon—The nest is messed up, eggs are broken or missing and debris hangs from
the nest opening. Use a Noel coon guard to keep them out. This device is a 6” x 24”section of quarter-inch hardware cloth, molded into the shape of a rectangle a little smaller than the front of the bird box. One edge is bent back to provide an area for screwing the guard to the front of the box.
House sparrow--Bluebird or Tree Swallow adults and young are pecked to death with their heads destroyed. The male sparrow often sits on the roof of the house and there is often nesting material in the box. Keep dumping the sparrow’s nest and trap them if you can. They are not a protected species.
Snake—Eggs and nestlings are missing, but the nest is not disturbed. A large baffle around the post will discourage snakes.
House wren—The eggs, nestlings and sometimes the nest itself have been removed from the box and replaced with a pile of sticks. Male wrens are usually visible nearby. Avoid putting nest boxes in brushy areas.
NESTING SEQUENCE
Eastern Bluebird females begin to incubate as soon as their last egg is laid and it
usually takes 12 to 14 days before the chicks hatch.
Tree Swallows start to incubate the day before their last egg is laid and spend 13 to15
days incubating. As a result not all swallow young hatch at the same time.
Hatchlings-- Bluebird chicks are bright coral-pink with dark down in sparse tufts.
Tree Swallow young are pale pink with cream-colored down.
Days 1-12---Bird boxes can be checked up to the 12th day without causing harm to the
young. The young birds progress from tiny bare babies to being fully feathered in 12-
14 days.
Days 12-22---Both species are fully feathered and fledge between 18 and 22 days.
During this time the nestlings get restless and more active. Avoid opening the box after day 12 because the young may fledge prematurely and perish.
Open the box carefully and make observations as quickly as possible to avoid unnecessarily disturbing the birds. Keep a record of these observations.
Touching the nest, eggs, nestlings or adults will not cause the birds to abandon their nest.
At the end of the nesting season, (usually in mid-August) the nest boxes should be cleaned out. In late winter or early spring the houses should be checked again and any nesting material of mice, flying squirrels, etc. should be removed so the houses are ready by early March for new residents.
DOS AND DON'TS
Avoid walking on the grass directly from one box to the next--Raccoons may follow
human scent and find an easy meal.
Remove all House Sparrow nests and contents. Discard nesting material away from
the nest boxes.
Remove all mouse nests. They can find housing elsewhere. Avoid coming in contact
with either the mice or their nesting material.
PROBLEMS (Evidence and Suggestions)
Raccoon—The nest is messed up, eggs are broken or missing and debris hangs from
the nest opening. Use a Noel coon guard to keep them out. This device is a 6” x 24”section of quarter-inch hardware cloth, molded into the shape of a rectangle a little smaller than the front of the bird box. One edge is bent back to provide an area for screwing the guard to the front of the box.
House sparrow--Bluebird or Tree Swallow adults and young are pecked to death with their heads destroyed. The male sparrow often sits on the roof of the house and there is often nesting material in the box. Keep dumping the sparrow’s nest and trap them if you can. They are not a protected species.
Snake—Eggs and nestlings are missing, but the nest is not disturbed. A large baffle around the post will discourage snakes.
House wren—The eggs, nestlings and sometimes the nest itself have been removed from the box and replaced with a pile of sticks. Male wrens are usually visible nearby. Avoid putting nest boxes in brushy areas.
NESTING SEQUENCE
Eastern Bluebird females begin to incubate as soon as their last egg is laid and it
usually takes 12 to 14 days before the chicks hatch.
Tree Swallows start to incubate the day before their last egg is laid and spend 13 to15
days incubating. As a result not all swallow young hatch at the same time.
Hatchlings-- Bluebird chicks are bright coral-pink with dark down in sparse tufts.
Tree Swallow young are pale pink with cream-colored down.
Days 1-12---Bird boxes can be checked up to the 12th day without causing harm to the
young. The young birds progress from tiny bare babies to being fully feathered in 12-
14 days.
Days 12-22---Both species are fully feathered and fledge between 18 and 22 days.
During this time the nestlings get restless and more active. Avoid opening the box after day 12 because the young may fledge prematurely and perish.
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