by Myrna Pearman, Biologist, Ellis Bird Farm, Lacombe AB
sponsored by Audubon Workshop, The Wild Bird Specialists.
Few sights in nature are more beautiful to the eye than the flash of its iridescent blue, few sounds to the ear more delightful than its soft, melodious warble. Little wonder so many songs, stories and poems pay tribute the bluebird. Little wonder it has become the bird that universally symbolizes peace, happiness and all that is good.
Three species of bluebirds grace the North American continent. The Eastern and Western species are aptly named, with the Eastern Bluebird found in the southeastern part of Canada and through the eastern US. Its counterpart, the Western Bluebird, is found along the western edge of North America. Home for the Mountain Bluebird, whose range overlaps with the other two species, is a large swath through the west-central regions. Although it will nest at high elevations, the Mountain Bluebird is at home in a prairie coulee as it is in a high alpine meadow. While all three species of bluebirds can be easily recognized by their beautiful azure coloration, only the Mountain Bluebird is completely blue. Both the Eastern and Western Bluebirds are additionally adorned with bright red breasts. The females of all three species wear a more muted attire than the males, showing bright blue in their wing and tail feathers only when they fly.
In addition to their interesting coloration, bluebirds also have rather peculiar nesting habits. Unlike most birds, which are content to face the elements from an open nest, bluebirds will only complete their nesting cycle if they have a roof over their heads. In the wild, the forests’ most industrious carpenters, the woodpeckers, provide this accommodation requirement. Since woodpeckers prefer to make new homes each year, their old houses stand empty after only one season. The following spring, other birds - including bluebirds, tree swallows, house wrens and a host of other secondary cavity-nesting species - scout out and lay claim to these secondhand houses.
The bluebirds’ penchant for utilizing old woodpecker cavities is why they will so readily accept a human-built abode; a nesting box, in the eyes of a bluebird, is as perfect a home as one left behind by a woodpecker.
Bluebirds make ideal tenants - their needs are fairly simple, they will accept the most basic of housing, and they barter fairly for their rent by providing their landlords with insect-eating services, and by delighting all with their interesting antics, beautiful song and fabulous color.
Bluebirds aren’t big city birds. Rather, they prefer the quiet of suburb fringes, country pastures, golf courses, cemeteries and parks. Bluebirds are insectivorous during their nesting cycle, dining almost exclusively on ground-dwelling insects. They will readily accept human handouts of mealworms and bird grubs, often becoming so tame that they can be hand-fed. In addition to residing where there are plenty of insects, bluebirds also like to be provided with a perching spot-a sentinel from which they can survey their kingdom.
While the ideal habitat for bluebirds is an open area dominated by short grass and dotted with a few scattered trees, they will also take up residence in wooded areas. Unfortunately, these brushy habitats are the haunt of the House Wren, a boisterous little songster with the nasty habit of pecking the eggs and usurping the nests of other birds. Bluebirds may also choose to nest in farmyards, feed lots and other areas where humans and cattle are found together. Unfortunately, these areas are the almost exclusive domains of the belligerent and prolific House Sparrow. This aggressive exotic, which was introduced into North America from Europe in the mid-1800s, out-competes the gentler bluebird for nesting sites and often takes over the bluebirds’ homes by killing them.
In the northern parts of their ranges, bluebirds migrate south for the winter. In the southern regions, they are resident throughout the year. When the weather turns cold, bluebirds readily switch to a diet of berries.
Bluebird Nesting Box Basics
The ideal materials to use for nesting box construction include cedar, cypress, redwood or exterior grade plywood. The wood can be left natural, or the exterior can be painted or stained. In southern climes, the boxes should be painted a light color to minimize overheating. The actual design of a bluebird box matters little to the birds. However, every effort should be made to ensure that the box is well designed and constructed. At least one panel (top, side or front) should open for easy monitoring and clean out. The floor size should be at least 16 square inches (4 x 4) for Eastern and Western Bluebirds, and 25 square inches (5 x 5) for the slightly larger Mountain Bluebird. The roof should extend over the entrance hole to provide adequate shade and protection from the sun, the floor should have drainage holes, and each sidewall should have ventilation holes to provide a cross draft. The inside of the front wall should be roughened up so the young birds can successfully exit the box. A bluebird box should never have a perch.
Boxes for Eastern and Mountain Bluebirds should have an entrance hole of exactly 1 ½ in.; for Mountains, the size should be 1 9/16 in. In areas where the range of the Mountain overlaps with the other two, the larger size should be used. An entrance hole size of 1 5/8 or larger should never be used, as this may allow entry by another introduced pest, the European Starling. Excellent nesting box plans are available from the North American Bluebird Society.
Attracting Birds, Butterflies and Other Backyard Wildlife
This National Wildlife Federation book provides over a dozen step-by-step projects for families to do together, making getting back to nature easy, educational, and fun.
Bluebird boxes should be mounted to a tall support post, such as a piece of electrical conduit or water pipe. Wooden fence posts and single trees can be used in areas where there are no raccoons, snakes or other climbing predators. If further protection is required against predators, baffles or carnauba wax can be used on the mounting post. The ideal height for mounting a bluebird box is about 5 ft. off the ground. The entrance hole should face away from the prevailing wind and towards a single tree or shrub.
Setting Up A Bluebird Trail
While a lone nest box in a backyard may provide accommodation for a single family of bluebirds, a bluebird trail (a line of five or more boxes placed along a prescribed route) is an even more effective approach to appreciating and helping these delightful birds. Most importantly, a bluebird trail provides additional housing for the bluebirds. Thus, it can increase the local population of bluebirds and therefore contribute to a continent-wide conservation effort. Also important, however, is the fact that a bluebird trail can provide individuals and families with a fun, hands-on wildlife project. From box construction and mounting, to regular monitoring and maintenance, a bluebird trail can provide a wonderful window through which can be glimpsed the intricate workings of nature.
Setting up a bluebird trail is not a difficult task, as long as an area of proper habitat is chosen. As we mentioned earlier, bluebirds prefer open rural areas with scattered trees and sparse ground cover. Take the time to choose the trail area carefully, and plan to be rewarded with many happy tenants. Before establishing a trail on someone else’s property, be sure to obtain permission first.
Most bluebirders set their boxes out in tandem, placing two boxes 5 to 25 ft. apart. The reason for this practice is because of another delightful, native cavity nester, the Tree Swallow. Tree Swallows, which can be extremely determined when it comes to utilizing a box, will often chase the bluebird away from a box to which it has already laid claim. Since both species will tolerate each other nesting close by, the provision of two boxes will allow them to nest peaceably, side by side.
Bluebirds have fairly large territories, so will rarely nest closer together than 300 feet. To minimize vacancy rates, boxes (or pairs of boxes) should be set at least this distance apart. Bluebirds are true harbingers of spring because, even in the northern parts of their range, they return to their nesting grounds early in the season-often by mid-March, when snow still blankets the ground. Upon his arrival, each male sets about to find suitable housing. When consensus is reached with his later-arriving mate, the pair commences with the demanding task of building the nest and raising their young. Boxes placed up in time for their arrival are more likely to be used than those set up later in the nesting season.
Nest box monitoring is interesting, educational and rewarding. It is also the key to operating a successful bluebird trail. Most bluebirders try to check their boxes weekly during the nesting season. Armed with a sense of curiosity and a pen and notepad, they carefully and quietly open each box to observe the goings-on inside. Notes are taken and the box quickly closed again. Most bluebirders keep records of such information as the species using the box, the number of eggs, number of young hatched and the number of young that successfully take wing (fledge). Records taken by thousands of monitors have established that it takes about a week for the female to build her tidy cup nest of grass or pine needles. She lays her clutch of 4 to 6 sky-blue eggs at a rate of about one per day, and spends 14 days incubating them. Both parents work tirelessly to keep their hungry, fast-growing brood fed. Although it takes about 17 to 21 days before the young actually fledge, box checks cease after the young are about 12 days old. This practice ensures that the older nestlings are not disturbed, since any untoward excitement will cause them to exit the box before they are ready. A prematurely fledged bluebird is unable to fend for itself, and is thus an easy target for any passing predator.
In addition to Tree Swallows, other species may also take up residence in a bluebird box. In the south, Carolina Wrens or Tufted Titmice may move in; in the north, Boreal Chickadees or Red-breasted Nuthatches might take up occupancy. With a bit of experience, it is easy to determine each occupant simply by the style and composition of its nest. All native cavity-nesters are welcomed tenants, but vigilance is often required to ensure that House Sparrows do not become established.
From time to time, problems and challenges may arise: a clutch of eggs may fall to prey to predators; the nest may become infested with parasites; or the young may succumb during bad weather. As bluebird landlords, every effort should be made to ensure that the nest boxes are constructed, mounted and maintained properly. No matter how diligent and dedicated a bluebirder might be, however, it is inevitable that some events are beyond human control. Boxes can be cleaned out as soon as the young fledge. They should be given a final inspection just before the bluebirds are expected to arrive back in the early spring.