Until fairly recently, Eastern Bluebirds (Sialia
sialis) were uncommon in many areas,
mainly due to loss of habitat open
and competition for nesting sites from
introduced species (starlings and house
[English] sparrows). However, bluebirds
are coming back. They are fascinating,
beautiful birds. You can help increase
their numbers. The keys are:
Neat, cup shaped, woven nest of 100%
fine grass or pine needles. Occasionally
bits of fur or a few feathers and rootlets. Fairly
deep nest cup. Eggs are powder blue,
sometimes white. NOTE: Western Bluebirds will routinely add ribbons, cellophane, feathers, thin bark and leaves to their nest. Note: Rare open-cup nests were found in surface-mined lands in KY and on oak limbs in SC.
House Sparrow: Jumble of odds and ends,
including coarse grass with seedheads, cloth, white
feathers, twigs and sometimes litter. Tall
nest, may have tunnel-like entrance.
Eggs are cream, white, gray or greenish,
with irregular brown speckles.
Nest of grass lined with feathers. May be messy. Flatter
cup than bluebirds. Eggs are pure white.
Black-capped Chickadee: Downy nest of moss, fur,
and soft plant fibers. Female may cover
eggs with moss when leaving the box. White
eggs with brown speckles.
Tufted Titmouse: Downy nest of moss,
fur, and soft plant fibers. May have
many earwigs living in it. White eggs with rose/mauve speckles.
House Wren: Messy nest of twigs, occasionally
lined with fine fibers or feathers.
Males may build unlined eggless "dummy nests" in
nearby boxes to reduce competition.
Tiny glossy white eggs, sometimes tinted
with pink/buff, with lots of fine pinkish
brown/reddish brown/brown specks that
sometimes form a ring on the larger
end of the egg.
or purchase a nestbox designed specifically for bluebirds. These
boxes are made of unpainted, untreated
3/4" - 1" wood or PVC,
have an overhanging slanted roof (2-5",
with a shallow saw kerf (groove) to keep
rain from entering the box), no perch,
a round 1.5" diameter hole (or
1.375" x 2.250" oval hole. Mountain Bluebirds need a 1 9/16" hole), ventilation,
drainage holes, are deep enough so predators
can't reach in and get to the eggs, and
have a door that opens for cleaning and monitoring
(if rough wood is not used, add kerfs to inside of door to enable fledglings
to climb out). Birds may roost in the boxes in cold weather, and the ground
may be frozen in February/March when they start house
hunting, so put boxes up in late fall
or winter. See plans.
up nestboxes in semi-open grassland
habitat, such as mowed meadows, large
lawns, cemeteries, orchards, roadsides,
and areas with scattered trees and
short ground cover. Areas with
fence lines, some medium size trees,
or telephone lines provide perches
for hunting and nest-guarding. If no native birds use the box for two years, try a different spot. (Note: Western Bluebirds do not favor large, open meadows.)
on 8 ft., 3/4" diameter galvanized pipe,
with the entrance hole 5 ft. off the
ground. If away from prevailing winds,
face E/N or NE.
a minimum of 125-150 yards apart. If nesting bluebirds
are harassed by Tree Swallows, or more than 50% of bluebird trail boxes are occupied by swallows, set up
a second, "paired" box 5-20 ft. from the first. Boxes that Tree Swallows nest in should have "kerfs" or grooves
(saw marks about 3/4" apart) or 1.5-2"
wide x 6" long plastic screen (gutter
guard) stapled tightly inside below
the entrance hole to enable fledglings
guards to keep snakes, raccoons and
other predators from raiding nests
(e.g., a 2-4 ft. long, 8" diameter
stovepipe or PVC pipe sleeve on the
pole, mounted (so it wobbles) just
under the box), even if you don't have
problems the first year of nesting.
Losses without predator protection
may run 25-33%.
chew the entrance hole to widen it, screw
a metal hole guard (available from birding
stores) or a
block of hardwood with a 1.5" entrance
hole over the damaged hole, or replace
the front part of the box.
strands of 10 lb. fishing line to boxes and feeders to scare House Sparrows. Sparrow
spookers made of mylar are VERY
effective - put them up AFTER the first egg is laid and remove after fledgling.
trees, shrubs, and vines that provide
fall and winter food for bluebirds. Consider
like a clean box. Remove bluebird nests
as soon as the young fledge, or if nesting
fails, to encourage another brood. Put
nests in the trash to avoid attracting
predators. If mice nest in the boxes
over the winter, clean them out in February. See instructions.
or repair any split, rotten, or broken pieces on
boxes that could let rain in and chill
See more tips. And be prepared to become possessed by
these captivating birds.
DON'T install nestboxes in brushy and heavily wooded areas, too close to trees or shrubbery. This invites House Wren attack.
boxes on trees or fence lines--they provide
easy access for predators. More info...
boxes near where pesticides or herbicides
are used. Don't use pesticides inside
boxes unless they are approved for caged birds.
hesitate to destroy House Sparrow nests and eggs. House Sparrows are non-native
invasive pests, and are not protected
by law. You might think they're
cute (some bluebirders refer to them
as "rats with wings"), but they will attack and kill adult bluebirds (sometimes
trapping them in the nestbox), and
destroy eggs and young. House Sparrow nests, eggs, young, and adults
may be legally removed or humanely destroyed under U.S. federal law. It
is better to have no box at all than
to allow House Sparrows to reproduce
corn, bread, milo, or millet in bird
feeders, as this attracts House Sparrows. Stick
with black sunflower seed, thistle (nyjer/niger/nyger)
and fruit. Or try a Magic
that monitoring will make the parents
desert the nest. Bluebirds tolerate
human presence. Touching the nest
will not make the birds leave--your mother
just told you that to keep you from harassing
them. Most birds don't have a good sense
DON'T monitor more often than 2x/week, or in early
morning (as eggs are usually laid 1-2
hours after sunrise)/evening/during bad
DON'T touch eggs while monitoring.
Some, especially chickadee eggs, are very
fragile. Also oil from hands could inhibit
the boxes once the birds are 12-14 days
old. (Their eyes are fully open
when they are 8-11 days old. Parents
may just dip their heads into the box
hole to feed the young at this age).
It can cause young to fall or hop out
of the nestbox before they are capable
of flying, reducing their chances for
DON'T paint boxes a dark color. (Light colors on the EXTERIOR only are acceptable.) If desired to preserve wood, coat exterior only with linseed oil or a product like SUPERDECK (Coastal Gray), and allow to dry thoroughly before box will be used.
the nest is abandoned. During egg
laying, adults may spend very little
time in the box. On hot days, the
female may leave the nest for long periods
of time. The only sure way to know the
nest is abandoned is if neither parent
has visited the nest for four full hours
after the young have hatched. If
it has been abandoned, contact a licensed
wildlife rehabilitator (e.g., Joan
Fuller 974-3265), the Audubon
Society or the North
American Bluebird Society.
discouraged if bluebirds don't nest in
your boxes the first year.
to Mid-March: Bluebirds start checking
out nesting sites. Late arrivals, or previously unpaired birds may nest as late as July or even August, and some pairs have multiple broods. It's never too late to put up a nestbox, as they may be used for a subsequent nesting (see Number of Broods), for roosting, and are also often checked out in the fall by birds that may return the following spring.
5-7 days. Usually laying one per day (skipping a day in cold weather is possible but uncommon),
for a total of 4-7 eggs. Often start
egg laying a few days after nest is
completed. Egg laying can be delayed (sometimes for a week or two - 3 weeks is not unheard of) in cold weather, for young parents, or in cases where food is scarce. In Connecticut, the first
egg is generally laid in April.
(Earliest reported in CT:
First week of March. Latest reported
in August - 3 broods that year. One
brood/year is more common in CT.) Later broods tend to have fewer eggs, and Bluebirds tend to lay more eggs per nest in the north vs. south, but southern birds have a longer nesting season.
12-14 days. While they may sit on eggs occasionally during the egg laying period, "full-time" regular incubation doesn't start until all
eggs are laid.
They may wait about a week if weather is still cold.
They may start incubating before the clutch is complete in warmer conditions. Hatching failure is highest during warmer conditions.
Hatching: May occur over 24-48 (rarely 72 hours)
16-21 days, typically 17-18. Occasionally a runt will fledge one or even two days later than the others. When they are first born, they look "a bit like hairy shrimp." Insect
availability may speed up or delay
fledging. If the box is empty in this time frame, the nest is flattened, and there is some fecal material (white) on the walls, it usually means fledging was successful. Once they leave the nest, bluebirds do not return to it. When the babies are 28 days
old, they can fly well. They can feed themselves by Day 30.
Number of Broods: One to four broods per year. Fourth brood attempts may be made in southern climates. The number of broods probably depends on timing, temperatures, food availability, box availability and the experience or age of the parents. A subsequent brood may be started within days or weeks of fledging the previous brood. It may be in the same box or a different box.
Food 68% of a bluebirds' diet is made up
of insects: grasshoppers, crickets, beetles,
and caterpillars. They
also like fruit -
e.g., flowering dogwood, holly, mulberry, wild
grape, Virginia creeper, pokeweed, and Viburnum. (Although
they will eat the fruit of multiflora rose
and Japanese honeysuckle, these are invasive
species, and should be eradicated.) Bluebirds
They may eat suet (see
link for recipes). Bluebirds rarely eat birdseed
(they will occasionally take shelled sunflower and peanut chips).
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in bluebird conservation.
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