Helping Bluebirds Survive and Thrive

Until fairly recently, Eastern Bluebirds (Sialia sialis) were uncommon in Connecticut, mainly due to loss of habitat, and competition for nesting sites from introduced species like House Sparrows. However, bluebirds are coming back.  They are fascinating, beautiful birds.  You can help increase their numbers. The keys are:

·         Learn to recognize nests and eggs

·         Put up nesting boxes (think location, location, location)

·         Control predators and house sparrows

·         Supplement food and water

·         Monitor nesting and maintain the nestbox

 

Learn to Recognize Nests and Eggs

·         Bluebird: Neat, cup shaped, woven nest of 100% fine grass or pine needles. Occasionally bits of fur or a few feathers. Fairly deep nest cup. Eggs are powder blue, sometimes white.

·         House sparrow: Jumble of odds and ends, including coarse grass, cloth, white feathers, twigs and sometimes litter. Tall nest with tunnel like entrance. Eggs are cream, white, gray or greenish, with irregular brown speckles.

·         Tree swallow: Nest of grass lined with feathers. 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.  Eggs are white with rose/mauve speckles.

·         House wren: Messy nest of twigs, lined with fine fibers and feathers. Males may build 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.

 

Put up Nesting Boxes

·         Use a nestbox specifically designed for bluebirds, following specifications approved by the North American Bluebird Society. Bluebird nestboxes should be made of unpainted 3/4" - 1" wood or PVC, have an overhanging (2-5”) roof that sheds water, no perch, a round 1.5" diameter hole (or an oval 1.375" x 2.250" hole), ventilation, drainage holes, deep enough so predators can't reach in and get to the eggs, and a door that opens for cleaning and monitoring.

·         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. However, it’s never to late to put up a nestbox.

·         Mount boxes on 8 ft., 3/4" diameter galvanized pipe, with the entrance hole 5 ft. off the ground. If away from prevailing winds, face the box East or South.

·         Keep boxes 125-150 yards apart. If nesting bluebirds are harassed by tree swallows, which are more common in our area, set up a second box 5- 20 ft. from the first. Boxes that tree swallows nest in should have "kerfs" or grooves (saw marks about 3/4" apart) below the entrance hole to enable fledglings to exit.

·         Put up nest boxes in semi-open grassland habitat, such as mowed meadows, large lawns, cemeteries or roadsides. Areas with fence lines, some medium size trees, or telephone lines provide perches for hunting and nest-guarding.

·         DON'T install nest boxes in brushy and heavily wooded areas, too close to trees or shrubbery where House Wrens are common, within 200 yards of barnyards where animals are fed, or where house sparrows are abundant.

·         DON'T install boxes near where pesticides or herbicides are used. Never use pesticides inside boxes.

 

Control Predators

·         DON'T mount boxes on trees or fence lines--they provide easy access for predators. Install predator 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.

·         If squirrels chew the entrance hole to widen it, screw a metal hole guard (available from birding stores like Birds In My Yard) or a 1.5" thick block of hardwood with a 1.5" entrance hole over the damaged hole, or replace the front part of the box.

·         DON'T 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 nest box), and destroy eggs and young.  House sparrow nests, eggs, young, and adults may be legally removed or destroyed. It is better to have no box at all than to allow house sparrows to reproduce in one.

·         Try attaching strands of 10 lb. fishing line to boxes and feeders to scare house sparrows. A Sparrow Spooker made of mylar is also effective. It should be put up after the first bluebird egg is laid, and removed after babies fledge.

·         DON'T feed corn, bread, milo, or millet in bird feeders, as this attracts house sparrows.  Stick with black sunflower seed, thistle (niger) and fruit.

 

Provide Food and Water

·         Plant native trees, shrubs, and vines that provide fall and winter food for bluebirds. Consider offering mealworms that you can buy online or at a pet store.

·         68% of a bluebirds' diet is made up of insects: grasshoppers, crickets, beetles, spiders, and caterpillars. They also like fruit- e.g., flowering dogwood, holly, red or black 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 love mealworms They may eat peanut butter suet. Bluebirds rarely eat birdseed (they will occasionally take sunflower chips).

·         Put up a shallow birdbath. Birds are attracted to dripping or misting water set ups.

 

Monitor and Maintain

·         Monitor boxes weekly to check on progress and control House Sparrows, blowflies, etc. DON'T worry 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 songbirds don't have a good sense of smell.

·         DON'T monitor more often than two times/week, or in early morning/evening/during bad weather.

·         DON'T touch eggs while monitoring. Some, especially chickadee eggs, are very fragile. You can remove eggs that have not hatched 5 days after last egg hatched.

·         Bluebirds 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.

·         DON'T remove tree swallow, tufted titmouse, wren, or chickadee nests. It is illegal to disturb a nest with eggs of any bird except house sparrows, starlings and pigeons, which are not protected. Empty House Wren nests can be removed.

·         DON'T open the boxes once bluebird babies 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 nest box before they are capable of flying, reducing their chances for survival.

·         DON'T assume 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.

·         Replace any split, rotten, or broken pieces on boxes that could let rain in and chill nestlings. 

·         DON'T get discouraged if bluebirds don't nest in your boxes the first year. Be patient! And be prepared to become possessed by these captivating birds.

 

 

Bluebird Timetable

·         February to Mid-March: Bluebirds start checking out nesting sites.

·         Nest building: 2-6 days.

·         Egg laying: 5-7 days. Usually laying one per day, for a total of 4-7 eggs. 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 or two broods/year are more common in CT.)

·         Incubation: 12-14 days. Doesn't start until all eggs are laid. They may wait about a week if weather is still cold.

·         Fledging: 16-21 days. When the babies are 28 days old, they can fly well.

If you keep track of dates, you will be able to avoid opening the box after the young are 13 days old, to prevent premature fledging.  Bluebirds may raise 2-3 broods in one season. Some studies have shown that 30% of bluebirds return to previous nesting sites the following season.

 

This guide was reproduced with permission by my friend Bet Zimmerman at www.sialis.org

If you go to my blog, The Birder's Report, you can download a more comprehensive Bluebird Monitoring Guide