A flash of blue whizzes past, and you wonder if you really saw it, so fleeting is its presence. The outdoors is full of the sights and sounds of countless birds in spring, so what is it about the bluebird that holds us spellbound?
In last month's column we explored a little about the biology of the Eastern bluebird, and I related the story of my own close encounter with a pair of them on a recent sunny day. The sky blue on its back, the rufous orange breast and white belly delight us and cause the bird to speak of springtime as no other bird can. The species is common in east-central Illinois, yet is at the same time elusive and cannot be found just anywhere.
Bluebirds feed most often on insects on the ground and they prefer wide open spaces with grassy meadows, scattered trees, fence lines and overhead wires for perching. It is from these varied vantage points that they can easily spot their prey. They seem to prefer locations that back up against a woodland and face out onto wide open fields. They take insects from wherever they can find them, and rely heavily on crickets, beetles, grasshoppers, and caterpillars. The softer bodies of spiders, moths and butterfly larvae are preferred for feeding the young nestlings. But the Eastern bluebirds will also add fruits to their diet, especially those of many berry-producing trees and shrubs.
Building their nests in cavities, the bluebird is considered a secondary cavity nester because it does not have the ability to create its own nesting space. The beak of the bluebird is not strong enough to withstand the constant hammering required to penetrate and excavate the wood of dead trees, as is accomplished by many primary cavity nesters such as woodpeckers. The bluebird therefore must rely on pre-existing holes, and will often find it hard to locate suitable nesting sites. Not only are they sometimes hard to come by, but there is often fierce competition for available nesting locations from other cavity nesting birds such as swallows, tree sparrows, and other bluebirds. One solution to this problem is for humans to provide and promote the use of artificial nest sites, called nest boxes or birdhouses. For many years wildlife biologists, ornithologists, and birdwatchers have successfully addressed this habitat shortage by mounting series of bluebird houses, called bluebird trails, in suitable locations throughout an area. Though the populations of bluebirds suffered severe declines in the 1940's and 50's due to habitat destruction and pesticide use, the use of nest boxes in their recovery is a true conservation success story. In just a few years, bluebirds have rebounded beautifully to healthy populations in many parts of the country.
How do we attract this springtime beauty to our own homes and gardens? Setting up bluebird boxes in late February and early March may seem early, but the males often come back before the females during these months to scout around for possible nesting sites. here are several things to think about if we want to be successful landlords and adequately address the needs of the bluebird families. Following are important points to consider:
Is my site suitable for nesting and feeding? Bluebirds prefer wide open areas with many fences or trees for perching. The location should be pesticide-free. Backyards in the middle of towns or urban areas are generally not attractive to bluebirds.
Where should I place the bluebird house or houses? The location of the house is extremely important for successfully attracting a mating pair. Place it at least 100 yards away from wooded areas, shrubbery, and treelines. Resist the temptation to mount the box on a tree or fencepost. Mounting it on an 8-foot length of 1/4 inch (inside diameter) galvanized pipe sunk about 2 feet or so into the ground will put it at eye-level and make it easy to check and clean. The free-standing pipe also lets you put it wherever you choose, in the best place for successful nesting. It won't rot, and the small diameter means that you can easily mount predator baffles if needed. Face the box away from prevailing winds, usually facing south. But if you must turn the front of the box a little to make it easier for you to see the hole, the birds won't mind too much.
How should I space the boxes if I put up more than one? Place the boxes at equal distances, about 125 to 150 yards apart. Bluebirds can be quite territorial and don't like to nest close to each other. An exception to this may be if a competitive species such as a tree swallow has set up housekeeping in one box, then a spare box set up 5 to 15 feet away can encourage a bluebird pair to nest without having to actively compete for the same nest box. They will often coexist peacefully alongside the swallows long enough to raise a brood of nestlings.
If I see bluebirds flying in and out, do I need to check inside the box or monitor it in any way? Bluebird boxes typically have a side that opens up so you can look inside the box without disturbing the nest, which is cup-shaped and made mostly of grass. Check on the box once a week during the nesting season—you may eventually find 4 or 5 light blue eggs that will hatch in 12 to 14 days. Once the baby bluebirds are 12 to 14 days old, stop monitoring the box. The babies will leave the nest when they reach 18 to 21 days old. Clean out the nest box as soon as the babies leave to encourage another brood, as the parents will often produce eggs twice in a season.
How can I attract bluebirds to my yard? Though not typically feeder birds, bluebirds can sometimes be attracted to our feeders with mealworms, suet, or suet nuggets. Some people have luck with chopped, soaked raisins, and sunflower or peanut hearts. Specially designed bluebird feeders are available that can exclude starlings or mockingbirds if they become a problem. Water in a bird bath or small pond is another attractant, as they will bathe often and with enthusiasm. They seem to prefer running or dripping water versus standing water, and flat rocks in the bottom help to gain a secure foothold.
Remember, bluebirds require little more than suitable nesting sites to maintain stable populations. We are enamored by them because they let us help them. They cheer us with their gorgeous coloring, and they embrace our efforts to bring them closer. And sometimes, all it takes is a moment of pure blue in the blink of an eye to make the world seem a brighter place.