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Eastern BluebirdAttracting Bluebirds
Bluebirds are one of the most admired birds in North America. The popularity of bluebirds has landed them in stories, poems and movies where they symbolize love, happiness and renewed hope. Individuals have increasingly become aware of the joys of viewing bluebirds and providing them artificial nesting sites.

Some of the earliest records of bluebird conservation came from the journals of Henry David Thoreau, naturalist and writer born in 1817. Thoreau's writings mention eastern bluebirds returning to their boxes, giving evidence that people were already providing nest boxes in the early 1800's, possibly even in the 1700's.

Eastern bluebirds seem to have been common at this point in time and somewhat stable until the introduction of two bird species from Europe the house sparrow in 1850 and the starling in 1890. Starlings and house sparrows use bluebird habitat and compete fiercely, forcing birds out of usable spaces or even killing them. Both the exotic house sparrow and starling spread uncontrollably and were widespread by the early 1900's. At this time, the population of bluebirds began to fall in response to both the presence of too many house sparrows and starlings and the loss of suitable habitat.

Individuals recognized the shrinking populations of bluebirds and began creating bluebird "trails"--series of nesting boxes placed along roads, around the 1930's.

The continuation of this effort on a larger scale from the early 1970's to the present time has undoubtedly had a significant effect upon the return of bluebird populations.

Bluebirds belong to the thrush family, Turidae, whose members are known for their singing ability. The Turidae family is comprised of 19 species including the popular American robin. There are three distinct species of bluebirds; the eastern, western and the mountain bluebird.

The coloration of the eastern bluebird differs somewhat between adult male and female birds. The male is dark blue on the head, back, wings and tail. It is reddish brown from the chin down over the breast. The belly is white. Females are a lighter blueish-gray on the back, wings, head and tail. They also have a lighter reddish color on the breast and are white on the belly. Some females appear almost all brown while others are more similar to the adult male.

The adult male mountain bluebird is sky blue on top of the head, back, wings, and tail. It is lighter blue from the chin to the belly and gray-white on the lower belly and under the tail. The female is greyish on the head, back, throat, breast and flanks. The wings and tail are sky blue. Mountain bluebirds are slightly larger than Eastern bluebirds. They measure about five inches in length and have longer wings, which extend about three-fourths the length of the tail when folded.

Male Western Bluebirds have deep blue upperparts and throat, with some rusty coloration on the upper back. The breast and flanks are chestnut, and the belly and undertail coverts are grayish white. Females look similar, but less colorful: brownish gray above, with breast and flanks tinged with chestnut. The throat is pale gray, and a prominent white eye ring is evident.

Feeding
Bluebirds feed primarily on insects, crickets, spiders and beetles in the spring and summer. Perches such as fence posts, fence wires or highlines are often utilized to view for unsuspecting insects. If perches are sparce, bluebirds will hover overhead much like a hawk in search of prey. Bluebirds will utilize wild fruits, berries and seeds during the fall to prepare them for their migration south.

Breeding Behavior
Once a female arrives on the territory, the male will begin a variety of behaviors which will attract a female and tend to call attention to the various nest holes on the territory. For example, the male may repeatedly poke his head in and out of a nest hole or cling to the side of the box and do a wing-wave display, flicking one or bothg wings open at a moderate speed.

Once both birds go into the nest box several times, they are generally considered paired and will likely use that particular nesting site.

An accepting female will begin nest building shortly after they have paired. At this point, the male begins what is termed mate-feeding where he collects food and feeds it to the female. They keep in touch by calls and visual displays as they fly about the territory.

The male follows the female closely as she forages and builds the nest. The male is close by both signaling her when it is safe to fly out of the nest box and to prevent other males from mating with her. Copulation can take place anytime from the beginning of nest building until the start of incubation. It generally takes place close to the nest box and may occur on top of the box itself.

Nest Location
Bluebirds are cavity nesting birds meaning they naturally nest in a hollowed-out area in a dead or dying tree. This is different from other songbirds such as robins and finches that build a cup-shaped nest in the branches of trees or birds like the meadowlark or horned lark that construct nests on the ground.

They are further considered secondary cavity nesters because they cannot excavate their own cavities in tree trunks such as woodpeckers which have heavy bills adapted for heavy pounding.

Today, one of the most utilized nesting locations for bluebirds is the man-made boxes that mimic the natural cavities provided by dead and dying trees. This habitat has been limited throughout the years by removal of old trees thought to be of no benefit to wildlife.

In addition to natural and man-made cavities, bluebirds have also been observed using crevices in rocks and cliffs, drain pipes, mail boxes and old farm machinery.

Nest Building and Incubation
As discussed earlier, the male bluebird takes the lead in exploring habitat and attracting a mate but the female is the one who makes final determination of where the nest is built. This process can be swift or it may take weeks. The time utilized in this effort is usually dependent upon the birds experience and whether they had previously nested in that same location.

Females are in charge of all the actual nest building. At times, the male may carry some nest material but this seems to be a behavior to stimulate the female to nest build and does not amount to much in overall creation of the nest.

A nest normally takes around six days to complete but may be interrupted and begin at a later date. All of this is dependent upon weather and individual bluebird habits. Pairs normally spend less time building nests for their second or third broods.

During egg laying, the female leaves the eggs unattended and begins incubating after the last or second to the last egg is laid. She is also in charge of incubating the eggs by herself. One reason for this is that she develops a brood patch consisting of an area on her breast where feathers are lost and blood vessels increase. This allows her to keep the eggs at the right temperature for development, a task the male could not perform.

During incubation, the female attends to the eggs almost constantly. Eggs are incubated throughout the night and during the day except when she leaves the nest to preen herself or feed. On hot days, eggs may be left for longer periods of time since they maintain adequate temperatures without her help.

While the female incubating, the male may come by and sing or bring food. It may be a signal that no predators are nearby and that she can safely leave the nest. While she is away, the male will remain close by and may even enter the nest box. At night, the male may sit next to the incubating female.

Incubation for both species is about two weeks but can be affected by weather. In cold springs, incubation can actually take somewhat longer if eggs experience periods of cooling.

Preferred Habitat
Selection of proper habitat to place several boxes or establish a bluebird "trail" is vitally important. Most people make the initial mistake of placing boxes in inappropriate locations. These decisions either create disappointment or may actually benefit recruitment of unwanted and undesirable birds such as the house sparrow.

Bluebirds are insect eaters and less competitive for nesting space than are other cavity nesters. Therefore, placement of nest boxes should be in locations away from heavily wooded habitat preferred by tree swallows and house wrens and near open fields where insect hunting, maneuverability, and visibility to avoid predators is adequate.

Generally, open rural country with scattered clumps of trees or low shrubs is best. Placing boxes too close to shelterbelts and wooded areas will attract house wrens and tree swallows, which are also beneficial bird species. Examples of good habitat include pastures, fields, edges of country roads, cemeteries and golf courses. The closer you get to buildings or urban areas, the more chance you will have problems with house sparrows which will actually kill bluebirds and their young. It is also a good idea to avoid areas where insecticide use is high.

Type of Nest Box
The type of box to purchase or construct to attract bluebirds is a subject of much discussion and there are probably as many ideas as there are folks who maintain bluebird trails. Ideas come from personal experiences and you will certainly have your own opinion after a few years of monitoring a few houses. There are, however, a few basic ideas that have proven successful for producing bluebirds and these guidelines provide a good place to start. North American Bluebird Society approved bluebird houses are always recommended.

Wood is probably the safest and best material for nest boxes. Wood mimics the natural cavity, is readily available, easy to work with and provides good insulation qualities. The best woods to use are cedar or redwood which withstand the elements without being treated.

Choosing between different designs of wooden boxes available shouldn't preoccupy a majority of your time since most offer the same result for the birds. Simply insure floor dimensions are at least four by four inches for eastern bluebirds and five by five inches for mountain bluebirds. Avoid thin wood which will not maintain tolerable temperatures inside the box. Also, do not use varnishes or stain inside the nesting box. These may be poisonous to the birds.

Both ventilation and drainage holes should accompany any box. One-half inch vent holes in the side of the nesting cavity will insure proper temperatures are maintained inside the nest box. The same sized holes can be drilled into the corners of the floor to allow moisture to escape. Entrance holes for eastern bluebirds should be one and one-half inches in diameter and about one-quarter inch larger for the mountain species. Holes in an oval shape have also been developed now under the presumption that birds can access with less difficulty.

The box should not contain a perch and the roof should overhang the entrance hole to keep rain and sun away. The entrance hole should be about six inches from the floor of the nest box.

Finally, one of the most important aspects is that you allow easy access for monitoring. By hinging either the top, front, or one of the sides, birds can be checked at any time and nest boxes cleaned easily.

Placement of Nest Boxes
Before you begin putting out any nest boxes, take into consideration the location of preferred habitat which was discussed above. Some locations may not be suitable for bluebirds at all but will be excellent for other beneficial species such as the tree swallow.

Remember, a bluebird trail does not have to contain a hundred boxes, it can be comprised of as few as two boxes. The first step is to draw a sketch of your property as you walk it, visualizing potential locations.

Boxes should be located in pairs about 100 yards apart. Ten to twenty feet should be left between boxes in a pair. Pairing the boxes will allow a more aggressive species such as the tree swallow or house wren to nest in one of the boxes first while allowing the second box of the pair for a bluebird. This strategy is all based on bird behavior because many bird species will not allow another member of the same species to nest in close proximity to their own nest but will allow another species like the bluebird to nest.

Nest boxes should be attached to steel posts if possible. Seven foot smooth steel fence posts work extremely well and allow easy attachment. Wooden posts allow predators to climb and access nest boxes more easily. If you do use wooden posts, predator guards can be attached.

Don't attach nest boxes to dead or dying trees within a forested area unless you are attempting to attract house wrens, chickadees, or nuthatches.

The recommended height for bluebird houses is four to six feet from the ground. Bluebirds may nest in higher locations but monitoring, viewing and maintenance will be much more difficult.

Face the front of the nest boxes away from the prevailing wind and in an easterly direction to avoid the hot afternoon sun from shining into the access hole. More important than this, face the box in a direction in which the young fledgling birds can reach a perch within about 100 feet. If you are attaching boxes to existing fence posts within a cattle pasture, put the boxes on the side of the fence opposite that of the cattle so they cannot be broken off by the cattle.

If you don't have adequate habitat on your own property, consider approaching a landowner with your idea. Also, be sure to obtain permission before you attach any nest boxes to utility poles or other private structures.

Monitoring and Maintaining Bluebird Trails
Simply putting out bluebird boxes without checking progress throughout the nesting season can be doing more harm than good for bluebird populations. One of the most important reasons for monitoring is to prevent house sparrows from using the nest boxes. Monitoring also allows you to keep track of nesting results which are important for contribution to the local wildlife agency.

Begin checking bluebird boxes in mid-March and continue checking each box weekly. If you cannot find the time weekly, insure you check them at least once a month. The note card shown below is a good guideline and can be duplicated to provide one for each nest box.


Record your results of monitoring as you move around the trail, keeping the cards for reporting overall information at the end of the nesting season. Approach nest boxes and gently tap on the outside of the box. Many times the bird will fly off as you approach or when the box is disturbed. This is normal and the bird will return after you have checked the nest.

Females may also sit quietly on the nest as the door is opened. In this case, close the door and return later. Bluebirds are very tolerable of humans. All birds have a poorly developed sense of smell and touching around the box, eggs or birds will not cause the bird to abandon the nest. All of this is part of the enjoyment and learning associated with a bluebird trail.

There is one time that nest boxes should not be opened. This is the time period about ten to twelve days after the eggs have hatched. Young birds will have partially developed flight feathers at this time and opening the box may cause them to prematurely flutter to the ground and become food for predators.

If you are not quite sure of the exact age of the birds, it is best to play it safe and observe from a distance or open the door only a crack to peer in. Some folks have even gone as far as using a small dental instrument mirror to view inside the next box without ever opening the door.

On the fifteenth day after egg hatching, the birds should have fledged and the nest should be removed. Take the old nest out, as well as any dead birds, and move the material away from the area as this can attract predators.

Remove all house sparrow nests immediately. Be sure that any of these nests are, in fact, house sparrow nests.

House sparrows and starlings are not protected by law and should be disposed of. All other songbirds are protected and it is illegal to tamper with or harm their nests in any way.

After the nesting season is over, clean out the boxes and then recheck again in the following spring. Some people simply leave the doors open on the boxes to prevent small mammals from using them as nesting areas.

Controlling Competitors and Predators
Competitors
The goal of establishing a bluebird trail is to attract as many bluebirds as possible. There are obstacles that you will encounter with this goal in mind and an understanding of the threat should assist you in maximizing your bluebird return.

Some people consider tree swallows and house wrens as nuisance birds. In actuality, these birds are beneficial for insect control and they are protected by law. As discussed earlier, avoid placing boxes in habitat areas favored by these species. Generally, the closer to wooded habitat, the more likely you will attract these two birds.

House sparrows are the largest competitor of bluebirds and concern over their competition is justified. House sparrows are aggressive and out compete bluebirds for nesting space. They will actually destroy and dump eggs from a bluebird nest and kill both young and adult birds when encountered. The best method of preventing this from happening is to avoid placing boxes in areas close to known sparrow habitat-usually urban areas, farmyards and any other location close to human dwellings.

Next, monitor nest boxes closely and remove sparrow nests immediately upon initiation. If you observe house sparrows beginning to build a nest in a particular nest box, there are devices which can be attached to the entrance of the nest box which trap the live bird inside. Once caught, they can be destroyed. There are also large live traps available on the commercial market which will trap numerous birds at once and can be successful in removing local house sparrow populations.

Predators
In addition to damages that may be caused by other songbirds, a number of other wildlife species, domestic cats, and insects can be potentially harmful to bluebird production.

Even though predation is part of nature, steps can be taken to lessen the amount, especially in the case of domestic cats which are not part of nature and can be controlled. Raccoons, snakes and cats all must enter the nest box by climbing unless they can reach nest boxes by jumping from tree limbs or other objects that are located too close. By wrapping an apron guard made of sheet metal around the post about a foot under the nest box or by placing a four inch piece of PVC around the post, these species will not be able to access the nest box at all.

Hawks such as the cooper's and sharp-shinned and falcons like the kestrel eat songbirds including bluebirds. Again, this is entirely natural and should not alarm you. Hawks and falcons are only doing what they do to survive and this must be accepted. Bluebird losses can be limited by avoiding the placement of nest boxes underneath perches such as high line wires or in known raptor nesting areas.

Blowflies are a type of fly that lay their eggs in bird nests. The larvae that hatch from these eggs will feed by sucking blood from the young birds. Larvae will feed during the night and crawl back into nesting material during the day. To check for larvae, lift up the bottom of the nest and tap it gently. If you find any larvae, brush them out. If larvae are in extremely high numbers, discard all the old nesting materials, brush out the box, and fashion a new nest with fine grasses. Replace the nest and return the eggs.

Paper wasps and yellow jackets may also decide to take up residency in a nest box. Check on the bottom side of the roof when the temperature is cool in the evenings.

Insect nests can be scraped out with a putty knife or knocked out with a stick. Do not use commercial sprays.


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