How To Make and Enjoy Your Own Blue Bird Trail - Mr. Richard Wells

New York State Blue Bird Society, 10025 Middle Road, East Concord, NY 14055. (716) 592 – 9596

How many of us have seen a bluebird recently? The great majority of young people today have never seen a bluebird. Yet 70 years ago, bluebirds were among the most common songbirds in America.

Bluebirds are an asset to farmers and gardeners because their diet consists almost entirely of insects in the spring and summer. In the late fall and winter they live largely on wild berries.

The eastern bluebird population may have plummeted as much as 90% due to shortage of natural cavities for nesting, competition from house sparrows and starlings, and pesticides. What is needed is a widespread effort to help the bluebird in its struggles and an easy way to help is to provide nesting sites.

Bluebird trails are becoming increasingly popular and are a source of great pleasure and satisfaction to those who operate them. A bluebird trail consists of a number of nesting boxes spaced 100 yards or more apart and so located that they can be conveniently monitored by going from box to box by car, bicycle or on foot.

A bluebird trail may consist of only a few nesting boxes on one’s own property or of hundreds of boxes spread over a distance of many miles. Bluebird population has increased dramatically along the routes of virtually all bluebird trails that have been operated successfully for a number of years. What is needed is a great increase in the number of bluebird trails, so that bluebirds can again raise their families in the vast areas where the natural nesting cavities have either been destroyed, or have been usurped by the alien starlings and house sparrows, against which the bluebird cannot successfully compete.

To operate a successful bluebird trail it is important to know the characteristics of the bluebird and the problems involved in maintaining a productive trail.


Because of their early return to the northern parts of their range, the bluebird today remains a symbol of springtime. The lengthening days of late February and March bring with them the arrival of bluebirds in search of suitable nesting sites. The male usually returns before the female and immediately starts searching for several unoccupied cavities or nesting boxes he considers suitable for nesting. Bluebirds are a cavity-nesting species and they nest and raise their young in holes of dead trees, fence posts, or in nest boxes.

Bluebirds are insectivores; they feed on a large number of insects that are harmful to crops (especially cutworms and grasshoppers). An exposed post, wire or branch is used as a perch for scanning the ground for insects.


Through singing and tail and wing displays, the male urges the female, upon her return to explore the cavity he has shown her. The male will show the female several sites, and hopefully, she will choose one of them. If she approves, the female accepts him as her mate and the pair will then stay close by until nest building begins.


Days and often weeks elapse between selection and actual start of nest building. In most areas nest building is generally underway in early May.

The female builds the nest almost entirely by herself. However, the male will accompany her while she collects the nesting material. The 3-4 inch wide nest is made of woven grasses and occasionally pine needles, where available. It usually takes 5-6 days for the nest to be completed.

Bluebirds time their activities so that the first egg is laid 4 to 5 days after then nest has been completed. One egg is laid each day until the clutch is complete. Three to six, commonly four or five, pale blue (occasionally white) eggs are laid. Incubation begins as soon as the last egg has been laid. The time of incubation is generally 14 days.


On the day they are hatched, young bluebirds are virtually naked. They weigh roughly one-tenth of an ounce. They are fed small, sort insects every few minutes from dawn to disk. The male bird does most of the feeding at first since the female must spend a good part of her time brooding the babies to keep them warm. Within about 12 days, the weight of the young bird approaches that of the adult. The natal down has been shed and replaced by the beautiful soft gray and blue juvenile plumage.

Young bluebirds usually leave their nests at the age of 17 or 18 days. On the day of fledging, the parent birds seem to encourage their young to leave the nest by restricting their food and by calling to them repeatedly in an enticing manner from a short distance. Each young bird at the moment it leaves the nest makes a valiant and usually successful attempt to fly to a nearby tree or bush. Most young bluebirds are capable of flying 50 to 100 feet on their first attempt. The newly fledged bluebirds soon work their way into the higher branches of nearby trees and remain high off the ground, flying from tree to tree to gain strength.

For the first 7-10 days out of the nest, the young are fed by their attentive parents. The bluebird fledglings start finding a small part of their own food when they have been out of the nest for about two weeks. Within another week or 10 days the young birds learn to obtain all of their own food. Bluebirds have strong family ties, so the young birds usually remain fairly close to their parents throughout the summer and early autumn. Often not more than 3 or 4 days elapse between the time the young of one brood are fledged and the nest for the next brood is started. Usually a second brood is raised by the same parents and sometimes also a third.

It is recommended that after the young have left the nest, the box should be cleaned as this increases the chances that a second brood will be raised in the same box.

Typical bluebird nesting timetable for this area.

March 15- bluebirds sighted in the area
March 30- female accepts box – bits of straw in box
April 22- female building nest
April 29- 5 blue eggs (usually one a day for 5 days)
May 18- young hatching, female carries away shells and fecal sacs
May 21- female continues brooding the young – both adults feed young from dawn to dusk
June 6- young bluebirds have left the nest – clean out the box
June 20- female begins building new next and process is repeated.


Where you choose to place the box is as important as how the box is designed. Bluebirds are birds of open areas. They rarely nest in wooded areas, but will nest in clearings. Open areas with scattered trees are best. Open fields are suitable if there are posts or wires for perching. Look for any area where the vegetation is kept short by mowing, or grazing such as parks, campgrounds, pastures, large lawns, cemeteries, golf courses and abandoned orchards. Generally bluebirds nest only in rural areas and the very outer edges of suburban developments. Proper placement of your nesting box (boxes) can encourage bluebirds and discourage other competing birds and predators.

Bluebirds -- We recommend that nesting boxes be mounted on 6 to 6-1/2 feet pipe. The boxes should be mounted 4 to 5 feet from the ground. It is recommended that they be placed 100 yards apart because bluebirds establish a territory during the nesting season and a nesting pair will not allow other bluebirds to enter their territory.

Tree Swallows – are the birds most often found in bluebird boxes. To maximize your chances of attracting bluebirds amidst competition from swallows we recommend placing two boxes 5-8 feet apart. Swallows will exclude another pair of swallows from nesting this close. Swallows only defend their nest site itself. This leaves the adjacent box open to bluebirds.

House Wrens like more bushy areas. To avoid competition with the house wren place the bluebird nestbox in more open areas at least 50 feet or more away from brush and woods.

Face the box towards a tree, shrub or pole so the young can fly toward it. Your nesting box should be put up and ready for use by the end of March if possible. If they are put up later than this time, they still should be attractive to bluebirds who are raising their second or third broods. Be patient, it may take several seasons for bluebirds to find your box!

Bluebird Nestbox Construction Tips

Back 14 x 6-1/2", Sides 10-1/2 & 9 " x 5" Top 12 x 8" Base 5 x 5" Front 9 x 6 " Entrance exactly 1 diameter located 1 down from top. Lower sides " from top for air vet. Nip off corners of base for drainage.

This plan can also be used for a side-opening box with a 4" x $" floor simply by making all boards one inch narrower and the top and bottom boards one inch shorter. For those who can secure the construction materials and have the tools to work with, it is an enjoyable project to build nesting boxes. For others, it is more practical to purchase the nesting boxes.

For detailed nest box plans for a side-opening box or a Peterson box or for the purchase of a nest box, contact New York State Bluebird Society, 7638 Erie Street, Pulaski, NY 13142, 315-298-2277


Bluebirds have to deal with many predators. Several mammals, reptiles and even insects prey on adults, young and eggs of bluebirds. These animals include raccoons, red squirrels, domestic cats, and a parasitic insect called the blowfly. House (English) sparrows and starlings are vicious competitors.

House Sparrows and Starlings. Competition between the bluebird and the starling and house sparrow for those few nesting places that remain has been a major factor leading to the decline of bluebirds. These two species, both brought here from Europe, are very aggressive and often force bluebirds always from nesting sites. Starlings, although larger than bluebirds, also compete for nesting cavities and food. During the winter, large flocks of starlings can strip plants of their berries leaving nothing for other birds.

Competition for nesting sites between bluebirds and starlings can be controlled by making entry holes exactly 1 inches in diameter. Unlike the natural cavities, which often have slightly larger openings, the starling cannot enter a box of this size. This opening still will leave bluebirds vulnerable to starling predation if the entry hole is less than six inches from the floor. Unfortunately, the house sparrow is not so readily excluded from a nesting box because they can easily enter an opening of 1 inches.

When a house sparrow wants a cavity occupied by bluebirds, it will attempt to drive the native species away. The bluebird’s small bill makes it a poor competitor in flights when facing the strong and heavy-billed sparrow. Frequently house sparrows will puncture and remove bluebird eggs, or kill the nestlings or brooding adults by pecking their heads. Placing nesting boxes away from human habitation, especially barns, will reduce the chance of having this species usurp nesting boxes. Also, keep the nest box low (4-5 feet). Sparrows prefer to nest at a higher site. These precautions are only somewhat successful.

Starlings and house sparrows, unlike all native birds, are not protected by federal law. It is recommended that all house sparrow nests be removed from bluebird nesting boxes as soon as nesting is initiated. Repeated removal of nesting materials may discourage house sparrow use, leaving the box available for native species. This is not legal to do with any native birds such as tree swallows or house wrens while they are actively nesting.

Nest removal may help in some instances, but the most efficient means of controlling sparrows is to trap them. Sparrow traps have been designed for use both within nesting boxes and on the ground. Trapping sparrows throughout the year can lead to great increases in bluebird productivity and distribution (Mail for sparrow trap information) Removal of sparrows from a n area is the most effective means of increasing bluebird numbers. And finally, any bluebird box when house sparrows are allowed to successfully produce young is worse for the bluebirds than no box at all.

Blowfly Larvae. Blowfly larvae parasitism has been severe in recent years. We have found many nests where blowflies have contributed to the death of nestling bluebirds or swallows. The female blowfly will lay 50-200 eggs in the bluebird’s grass nest, usually when the fledglings are first hatched. More than one blowfly may lay eggs in the nest. The eggs hatch in 1 to 2 days into tiny tan colored larva that turn brown as they approach 3/8" long.

The larvae attach to the nestlings’ feet, legs, underside of wings and breaks and draw out the blood and body fluids. The larvae attack the nestlings at night and hide in the nesting material during the daylight hours. Researchers have found as many as 250 larvae in one nest. During recent years, approximately 80% of the nests were infested. The larvae feed on the fledglings for approximately 8 days and then go into a dormant stage for 3 days where they become leathery and enter the pupa stage.

After 10-12 days the adult blowfly emerge from the puparia and fly away in search of fresh bird nests where they will be able to repeat the 3 to 4 week life cycle. Therefore, the incidence of blowfly infestation usually increases in the second and third nestings as the summer progresses. A heavy larvae infestation may kill the nestlings outright or seriously weaken then so they are unable to leave the nest.

Monitoring your nesting boxes for blowfly larvae is one of the most important things that you can do to increase the bluebird population. Once the nestilings are hatched, check the nesting box every 3 to 4 days (Do not disturb the nestlings after 12 days or they may fly from the nest prematureely.) Open the nesting box, lift the nest slightly and carefully scrape the chaff from the bottom of the nest into your hand. If blowfly larvae are evident, change the nest.

Remove the nest and nestlings and clean the box thoroughly. Next, build a new nest of dried lawn clippings similar to the shape of the original nest and pack it down tightly. Gently replace the nestlings. The parents don’t object; songbirds have a very poor sense of smell. Be sure to destroy the fly larvae and the old nest.

Raccoons. Raccoons are a common predator of Eastern Bluebirds and other cavity-nesting birds using nestboxes. At the present time the raccoon population is excessively high and nestboxes are more susceptible to the ravages of the raccoon. Raccoons commonly will climb up to the nestboxes and remove eggs, nestlings, or even incubating adult birds. Even when raccoons cannot reach into the box they may harass incubating or brooding adult birds enough to cause nest abandonment.

When mounting a nextbox on a pipe, applying a heavy grease on the pipe appears to be effective. You can put sheet metal guards on the pole below the bbox to keep predators from climbing up. Recent experiments have demonstrated that a 5" extended over-hang of the roof acts as a deterrent and yet is acceptable to the bluebird.

The raccoon attacks from the top of the box and the 5" over-hang deters the raccoon from reaching in the entrance. The longer over-hang is also a help in keeping rain or hot sun from entering the box.

MONITORING BLUEBIRD NESTING BOXES. Your box may contain any of the following nests:

  1. Bluebird. Neatly constructed of grass, the 4-5 eggs are pale blue or occasionally white. If it has been over 15 days since eggs hatched and you find a well-flattened nest not disturbed, this indicates that the nestlings have fledged. Remove the old nest (only if there is no sign of a new nest being built) promptly because this will encourage bluebirds to nest again in that box.
  2. House Wren. The nest is large and made of twigs. The 6-8 eggs are white, speckled with brown.
  3. Tree Swallow. The nest is of woven grass, and lined with feathers. The 4-6 eggs are white.
  4. House Sparrow. A mixture of course grass, feathers, and trash make up these very large woven nests. Usually there are 5-6 gray-white eggs, speckled with brown.
  5. Chickadee. The nest is made of moss, plant down and lined with hair and animal fur. The 5-8 white eggs are speckled with reddish-brown.

It is important to the recovery of the bluebird that all nesting boxes be frequently monitored to detect blowfly and/or use by house sparrows. Uncontrolled, these species will continue to place the survival of the bluebird n jeopardy. Bluebird boxes that are placed in the field and not monitored may do more harm than good to bluebirds.

It’s a good idea to inspect the nestbox after a heavy or prolonged rain. If you find the nest quite damp or wet change the nest. Remove the nest and nestlings and build a new nest of dried lawn clippings and replace the nestlings. You may lose the nestlings with respiratory problems in a wet nest if you don’t follow this procedure.

Check in early spring to see if the deer mouse or white-footed mouse has occupied the nestbox during the winter. If so, remove the contents. Then your box will be ready for the next bluebird occupants.

For further reading order THE BLUEBIRD, ITS FIGHT FOR SURVIVAL by Lawrence Zeleny, THE BLUEBIRD BOOK by Lilian Stokes, each $9.95 plus 10% handling, prepaid. Available from the NORTH AMERICAN BLUEBIRD SOCIETY, Box 6295, Silver Springs, Maryland 20906.

THE NEW YORK STATE BLUEBIRD SOCIETY was formed in 1982 in order to promote and develop an active bluebird conservation program that would help insure the continued growth of the bluebird population. The organization’s goals include cooperation with the North American Bluebird Society, and membership in that group is encouraged. NABS, Box 6295, Silver Springs, MD 20906.

Financial support for the New York State Bluebird Society is mostly through sales of the nesting boxes, membership dues and donations.

Join an organization dedicated to the recovery of the Eastern Bluebird? Your membership helps support the following activities:

New Members will receive a packet of bluebird information leaflets.
This Brochure may be reproduced by anyone to encourage interest in Bluebirds.

Order Brochures from:
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Duanesburg, NY 12056

We Invite you to Join! 


Richard Wells, President
9141 Cattaraugus St., Springville, NY 14141

Vincent Schneible, Sec.
106 Vernon Drive
Duanesburg, NY 12056

David Smith, Treasurer
15 Bridle Land
Dryden, NY 13053


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