During the past several decades, ornithologists have studied and studied reasons for the decline of all three species of bluebird indigenous to the United States. Generally, research agrees on three primary causes for the drastic drop in numbers of Eastern Bluebirds and for the less precipitous, yet noticeable, decline of the Western and Mountain Bluebirds. First, the loss of habitat has diminished numbers of birds from their former ranges as man has replaced bluebird territory with farm and city. Second, competition from two introduced birds, the European Starling and the English or House Sparrow, has favored the visitors. Finally, the use of insecticides hits both their intended targets as well as ones wholly accidental, among them all of America’s bluebirds.
All three species of bluebird are secondary cavity-dwellers: they build nests in cavities hollowed out by other creatures or by nature’s own decay. As more trees are felled by a growing human population, as fewer dead trees and limbs remain, and as our forests are being replaced by human habitation, fewer cavities are available to bluebirds. Some writers have even suggested that replacing old wooden fence posts with steel ones has reduced wood, thus cavities, for nests.
Added to this ever-shrinking habitat are the imported European Starling and the House Sparrow, both fiercer competitors than the gentler bluebirds and both very happy to build nests where bluebirds do. Further, the European Starling has often decimated berries the bluebird depends on for food. Thus, the bluebird suffers from imported competition as well as dwindling habitat.
Finally, bluebirds, along with the Bald Eagle and the Peregrine Falcon, have suffered from the unforeseen effects of DDT and other insecticides used so widely after World War II. These chemicals affect the bluebirds’ food supplies, insects and berries, or kill the birds directly.
Luckily, we can help alleviate some of these problems. The use of insecticides is more controlled and under more careful scrutiny each year. By leaving decaying trees and dead limbs where bluebirds need them, we can enhance their natural nesting places. Finally, the careful and dependable placement of nesting boxes in bluebird trails, rows of nesting boxes at set intervals, is helping these birds make a comeback. The Eastern Bluebird has, for example, begun to increase its numbers greatly, returning each year to man-made bluebird trails.
The State of Montana has systematically built, maintained, and monitored hundreds of miles of bluebird trails for all three species of these birds that occur in that state.
The plan of the Colorado Division of Wildlife and the Audubon Society of Greater Denver is precisely this. We want to know of bluebird trails statewide, to monitor these each year, and to build and place more of them, compiling reliable data which will direct further efforts to help these elegant little birds. Our program will be run by volunteers who will build boxes or explain how, direct their placement, monitor their success, and track changes year by year. Our boxes are suitable to Mountain and Western bluebirds, both indigenous to Colorado.
For the past several decades, much thoughtful and thorough research has been done by scientists whose studies are truly needed. It is, perhaps, as true, however, to conclude that one reason for this careful research is an aesthetic one, the delight we take from seeing the bird in its natural environment. This delight is, no doubt, akin to the happy shock one experiences upon seeing an electric blue Morpho Butterfly etched against the verdant Amazonian rain forest. In his fine book, The Bluebird, author Lawrence Zeleny quotes Frank M. Chapman, "one of America’s foremost ornithologists,...moved to express his feelings poetically in his classic Birds of Eastern North America:
The Bluebird’s disposition is typical of all that is sweet and amiable. His song wreathes of love, even his fall call-note — tur-wee, tur wee — is soft and gentle. So associated is his voice with the birth and death of the seasons that to me his song is freighted with all the gladness of springtime, while the sad notes of the birds passing southward tell me more plainly than the falling leaves that the year is dying."
As the advent of winter in Colorado is preceded each autumn by the fall of golden leaves, it also anticipates the rebirth of another year, greeted in spring by new, green aspen leaves and returning birds, some of them blue. It seems the bluebird, a part of this natural cycle, could use some help from us.
Following are more details designed to increase the blue among the green.