Wild Bird Center of Boulder March '09 eNewsletter

Some of my most memorable natural history experiences have occurred while I'm in the car. (Perhaps I spend too much time in there?) For example, a few months ago a mountain lion bounded across the road about 40 feet in front of my car. I will always remember the graceful stride and expression on the cat's face. Events like these are recorded on mental videotapes that I can play back anytime--pleasant memories. One such memory, which I always play back at this time of year comes from four years ago.

The morning after a big upslope snow in March I was driving on Foothills Highway near Neva Road. By chance, I glanced over into a ravine to the scene I shall always remember-snow-covered yucca with bluebirds. There were about 25 male mountain bluebirds perched on the snow and in two yucca plants near an old fence. With the sun on the new snow, all the birds were reflecting the intense cerulean blue of the morning sky. A scene for sunglasses. I wish everyone could have the experience of seeing a flock of male mountain bluebirds on freshly fallen snow. I really can't do the scene justice. I always think that mountain bluebirds must come with batteries, otherwise how could they be that blue? They seem to be lit internally.

The scene I stumbled across that morning is not unique. Bluebirds are known for their early returns from the south. Some may even spend the winter here in the relative shelter of the Foothills. Males migrate back before the females so they can establish territories and identify possible nesting sites for the females to review. It is possible to see all three bluebird species within the county, but mountain bluebirds are most common. In Boulder County, they nest in meadow habitats from 6000 feet to timber line.

Bluebirds are secondary cavity nesters which means they rely on other birds to produce holes. Bluebirds are dependent on nuthatches, woodpeckers, and sapsuckers for initially excavating holes and later leaving them for the bluebirds to use in subsequent years. These excavations are themselves dependent on other natural processes to produce dead trees and limbs in which they can make holes without tremendous effort. For example, primary and secondary cavity nesters are found in greater numbers within Colorado forests where mistletoe is present. The mistletoe often kills weakened trees and limbs. These dead trees and limbs are called snags.

Declines in bluebird populations have been a concern to many backyard bird watchers. These declines are a result of many factors, including loss of nesting opportunities. Humans tend to harvest or "clean up" dead trees and limbs, and this practice has led to a decline in the number of nest sites available to cavity-nesting birds. The switch from wood to metal fence posts on most farms and ranches has also reduced the supply of potential nest sites. Competition for nest sites is always high among secondary cavity nesters. And it has become increasingly intense. Aggressive non-native species, such as the house sparrow and European Starling, often drive bluebirds out of sites they have chosen. Backyard birders have tried to combat this loss of nesting opportunities by providing nest boxes for the bluebirds. Happily, their effort has been an important factor in the rebounding of Eastern Bluebird populations.

In Colorado, mountain bluebirds are regarded as a species of concern, meaning their population is in decline, but they are still common enough not to warrant extensive research or recovery efforts. The decline is attributed primarily to loss of snags. People living in the mountains and foothills can help reduce these declines by leaving dead trees and snags on their property when possible and by erecting nest boxes. With a little effort now, we can reverse the decline of the mountain bluebird population and remove it from the special concern list. I would hate to think of a future where people could not shoot their own mental "video-bites" of mountain bluebirds. For one it may be a memory of a female hovering over a meadow and then pouncing on a beetle, for another it may be a memory of bluebirds perched on a yucca in the snow.