A male eastern bluebird perches on an eastern redbud tree. Bluebirds are unique to North America, and at least one of the three American bluebird species graces every state except Hawaii and every Canadian province except Newfoundland.
PHOTO: RICHARD DAY/DAYBREAK IMAGERY
Everybody loves a bluebird. No other bird is featured more often in our prose, poetry, and song. The bluebird is the cheery little guy on your shoulder as you sing zip-a-dee-doo-dah. Bluebirds fly somewhere over the rainbow. “The bluebird carries the sky on his back,” wrote Henry David Thoreau. But there is substance, not just lyrical literature, behind our fondness for bluebirds. They have earned their place in our hearts.
Bluebirds occur only in North America. European settlers called them “blue robins,” because the birds’ size and rusty breast reminded them of English robins. Comparatively scarce in pre-colonial days, the American bluebird thrived as pioneers cleared forests and plowed fields, creating the open, woodland-edged habitat they favor. Orchards and field crops served up concentrations of tasty insects. Bluebirds nest in tree cavities, and farmers furnished housing by surrounding their fields with cavity-prone wood fence posts. At the turn of the 20th century, bluebirds were common in much of rural America, and even nested in urban residential areas.
The story changed soon after, however, when bluebirds were hit with a double whammy: House sparrows and starlings — aggressive European imports whose populations had burgeoned since their arrival on our shores — robbed bluebirds of their traditional nest sites, destroyed eggs and killed fledglings. At the same time, modern orchard pruning practices, routine removal of dead trees, and replacement of wood fence posts with metal drastically diminished the number of nesting cavities available to bluebirds. The use of DDT and other pesticides also harmed bluebirds. Their numbers nose-dived. “During the past 40 years,” wrote bluebird expert Lawrence Zeleny in the June 1977 National Geographic, “the population of the eastern bluebird may have plummeted by as much as 90 percent.” The birds, Zeleny said, had become “so scarce that most people under 30 have never seen one.” Extinction, he wrote, was “a real possibility.”
Zeleny’s alarming article, as well as his 1976 book pointedly titled The Bluebird: How You Can Help Its Fight for Survival, were wake-up calls to the public, and a movement was born. In 1978, Zeleny founded the North American Bluebird Society (NABS) to provide information on building and siting nest boxes, dealing with competing species, and nurturing bluebirds and other cavity-nesters. To this day, NABS and many similar state organizations continue to help people in the United States and Canada help bluebirds. Thanks to the organization’s advice and the efforts of countless people, bluebird populations are bouncing back in most areas.
The Blues Trio
Three bluebird species live in North America: the eastern (Sialia sialis), the western (Sialia mexicana) and the mountain (Sialia currucoides). At least one kind graces every state except Hawaii and every Canadian province except Newfoundland. The birds’ names pretty much tell you where they live. The eastern bluebird occupies the eastern two-thirds of the United States (except for extreme southern Florida) and southern Canada. The western bluebird’s range picks up where the eastern bluebird’s leaves off and extends westward to the Pacific Coast and south into Mexico. The two overlap in southern Arizona and, in winter, the Great Plains and west Texas, where they sometimes seasonally mingle.
The mountain bluebird shares much of the western bluebird’s summer range, but occupies high, open habitat — mountain meadows, high hills, and plains — while the western avoids exposed meadows and prefers open woods and forest edges at lower elevations. The mountain bluebird’s nesting range also extends farther north, through much of the western third of Canada (where it shares territory with the eastern bluebird) and north through inland Alaska.
Even in places shared by two or more species, there’s no problem telling bluebirds apart — at least not the distinctly colored males (in general, female bluebirds are paler and more subtly colored than males). Eastern and western male bluebirds both sport a rusty breast and a blue back, head, wings, and tail: the bird most of us probably picture when we think of bluebirds. The western male’s blue is deeper and richer than the eastern’s bright blue, but the birds’ bellies and throats really tell the tale. The eastern bluebird’s belly is white, and the rust color of its breast extends up over its throat, like a turtleneck. The western’s belly is light blue or gray, and the blue of its head extends down over its throat, like a ski mask. And the male mountain bluebird? It looks unlike either of the others: Its entire body is strikingly sky blue.
All three bluebirds are closely related members of the thrush family and share similar habits. In summer they eat mostly worms and insects, including many garden pests. The birds seem to relish a munch with crunch; grasshoppers are a favorite food. Perched on a post or branch, a bluebird will spot an insect on the ground, flutter-glide and land momentarily to grab it, then return to its perch — a behavior known as ground sallying. Eastern species do this less often, and mountain bluebirds most often — they hover-hunt nearly as much as a kestrel, North America’s smallest raptor.
Bluebirds also eat wild fruit, such as berries from cedar, juniper and sumac. Their diet shifts almost exclusively to fruit in winter. Only partially migratory, bluebirds in the northernmost parts of their range move south to reach a dependable food supply, while their southern cousins generally stay put.
Come spring, bluebirds that migrated south return to their nesting grounds, earning their reputations among Northerners as the trumpets of spring. Spring is also when bluebirds commence courting and homemaking. Males, which in the North arrive first, find suitable nesting sites and stake out territories. Perched in the highest branches, the male proclaims its presence in song — in the eastern bluebird’s case, sweet warbles, whistles, and chirps in varying combinations comprising a repertoire of about 50 different song phrases. Western and mountain bluebirds’ songs are somewhat less melodious — throaty churr notes in halting series — but the purpose is the same.
With luck, the male’s performances will gain a female’s attention. But it’s not just song that woos a mate. Studies show that the brightest, bluest males are quickest to catch the eyes of females. Even then, a male must convince an interested prospect that he and his nest site are worthy. For up to a week, depending on how coy the female is, he flits and flirts, warbling to her atop the nest site or perched nearby, bringing her choice morsels to eat, popping in and out of the cavity as if to say, “See? Try it!” She watches passively until the magic moment: She enters the hole and accepts his invitation.
Nest-building begins, with the female doing most of the work while the male looks on, warbling encouragement and flying in to intervene should a predator — or a stray Lothario looking to tempt his mate — come by. The nest is a tight cup woven mostly of grass, plant stems or pine needles. After completing it, the female lays her eggs one per day. To ensure her young will hatch at the same time, she starts incubating only after she has laid the entire clutch, which is usually four to six eggs. For the next two weeks, she leaves the eggs only often enough to feed herself.
Chicks hatch naked, blind and hungry. Atop each tiny, pink, fuzzy-downed body is an upturned, bright yellow mouth, gaping wide — imploring, “Feed me!” And so begins the parents’ marathon feeding frenzy, in which they take turns bringing food — caterpillars, grasshoppers, spiders and worms — to the babies roughly every 15 minutes from dawn to dusk. Not surprisingly, the baby birds grow rapidly. After a week and a half, their eyes are open and they have feathers. Within three weeks, they’re able to fly from the nest, though the parents continue to feed them until they’re 4 to 6 weeks old, when they can forage on their own.
Even before the fledglings have gained independence, the mother turns her attention to building a new nest for her next brood. Western and mountain bluebirds typically produce two broods per year, while eastern bluebirds have two, three or, rarely, four.
Attracting and Caring for Bluebirds
If you’re interested in attracting and housing bluebirds, you’ll not suffer for lack of advice. There is a flock of books, websites, and organizations dedicated to helping humans help bluebirds (see “Resources,” below).
Providing nest boxes is the first step. Not all “birdhouses” offer the essentials: protection from predators and weather, and dimensions that welcome bluebirds but discourage non-native bird species. The basics include sturdy, untreated wood, an overhanging roof to provide shade and shed rain, a top or side that opens, and a circular hole 1 1⁄2 inches in diameter for eastern bluebirds or 1 9⁄16 inches for western and mountain bluebirds (the hole size keeps out starlings). The box should be watertight, with drainage holes and air vents.
Properly locating a nest box is critical. An open area with low grass — such as a pasture or a large lawn — is ideal. Mount the box on a post or pole facing away from prevailing winds. If cats or raccoons prowl the area, use a baffle or some other predator guard that prevents animals from reaching the nest box. If you’re putting up more than one box, space them at least a football field’s length apart to provide sufficient territory.
Monitoring each nest box (opening it and examining the nest and eggs or chicks) is important during the nesting period. Once a week is recommended. Bluebirds tolerate humans — the parents won’t abandon the nest or kill their young as a result of your presence. Open the box carefully on a calm, mild day. You’re looking mainly for two problems: 1) the small larvae of blowflies, which parasitize and weaken the birds (you’ll need to remove the larvae and nest and replace it with a similar cup of dried grass) and 2) the tall, coarse-grass nest or cream-colored, brown-splotched eggs of house sparrows. As invasive, non-native birds, house sparrows aren’t protected by law (disturbing any native bird’s active nest is illegal) and their eggs should be removed to stifle further population growth. Be aware, however, that chickadees, house wrens, and tree swallows — which are native and beneficial — also favor bluebird nest boxes. Consult a field guide or an online resource to learn how to recognize their distinctive nests and eggs, and consider them welcome inhabitants.
When bluebird babies are 12 to 13 days old and almost ready to fledge, stop opening the nest box to avoid prompting them to leave prematurely. After all the chicks have left the nest on their own, remove the nest. This encourages the female to use the same nest box for another brood.
Spread the Love
Bluebirds are beautiful, pleasant to our eyes and to our ears. Their continuing rebound is thanks largely to the collective impact of countless human admirers taking steps to assure their survival. But bluebirds aren’t the only species that needs our help, of course. Some may not be as charismatic, and others may not be as tolerant of or responsive to human intervention, but all could benefit from the heartfelt caring we’ve shown bluebirds. You can start in your own backyard: Avoid using pesticides, protect the water supply, and plant native trees and shrubs that provide food and shelter for wildlife.
By spreading our affection beyond the beloved Mr. Bluebird, perhaps all species now threatened or endangered could someday bounce back. My, oh my, that would be a wonderful day.
Are Bluebirds Really Blue?
Scientifically speaking, the answer is no — bluebirds aren’t really blue, at least not in the sense that they get their color from chemical pigments. Nor are blue jays or indigo buntings or most other blue-feathered birds really blue. If you were to grind a bluebird feather to a powder, its color would be ashen gray.
The bluebird’s blue is called a “structural color,” caused when light is scattered and reflected by tiny structures within each feather’s myriad microscopic barbules. In the bluebird’s case, the feathers reflect short-wavelength blue light, creating the lovely hue that inspired Thoreau to say bluebirds carry the sky on their backs.
In nature, the color blue among vertebrates — birds and lizards, for example — is almost always structural. Oranges, yellows and reds, on the other hand, are generally pigment-based. There are some exceptions. A ruby-throated hummingbird’s iridescent greens and reds are structural colors. If you’ve ever watched a hummingbird, you may have noticed its color disappears at some angles.
For more information on bluebirds and how to attract and care for them, head to your local library or research online. Here’s a starter listing of helpful books and organizations.
The Bluebird Book: The Complete Guide to Attracting Bluebirds
by Donald and Lillian Stokes (Little, Brown and Co.)
The Bluebird Monitor’s Guide to Bluebirds and Other Small Cavity Nesters
by Cynthia Berger, Jack Griggs and Keith Kridler (Collins Reference)
North American Bluebird Society
To find a bluebird organization in your state, visit The Bluebird Box, or do an online search for “bluebirds” and the name of your state.