March 2008

On the Bluebird Trail

Give these little blue gems a good place to nest, and they'll entertain you for years to come.

By Mark Klym

Many urban Texans, and even much of our rural population, have never experienced the thrill of seeing the beautiful bluebird in its natural setting. The introduction of the house sparrow and European starling, the industrial revolution with the resulting migration of our human population into larger cities, and the shift from wood rail fencing to chain-link fencing combined to reduce bluebird numbers significantly in most states. Texas also experienced a decline, though the bird, thankfully, never really disappeared.

Bluebirds can be seen all over Texas, but in some regions they are more common than in others. Three species of bluebird occur in the state. The eastern bluebird (Sialia sialis), which is the common bluebird in most of North America, is also the common bluebird here, being found in good numbers almost everywhere. The western bluebird (Sialia mexicana), which is seen more commonly in the mountains of the Trans-Pecos, also experienced declines across most of its range. The mountain bluebird (Sialia currucoides), a species that does not nest in Texas, winters in West Texas but can be found in Central Texas some years.

By the early 1920s, conservation-minded individuals realized the bird was in trouble and began looking for a way to improve the outlook for the bluebird. Since nest cavities seemed to be the primary, though not the exclusive, cause of the decline, some landowners began using artificial cavities in the form of nest boxes or birdhouses to provide the birds with a place to nest. Thomas E. Mussleman and William G. Dunlap are credited with developing the concept of the bluebird trail, or a series of nest boxes strategically located to attract bluebirds but easily monitored to reduce predation. Bluebird trails are an increasingly popular way to attract and maintain bluebirds not only in rural settings, but also in some urban locations.

"The bluebirds were there, but we did not know it," says Dan Hanan, a bluebird enthusiast who created a bluebird trail on his blackland prairie property near Bastrop. "We became aware of the bluebirds when they promptly built two nests in our original 10 nest boxes."

In 2000, he received a wildlife tax valuation on his property in Bastrop County and managed for Neotropical songbirds as one of his targeted sets of species. He installed 10 nest boxes for bluebirds and began keeping a paper record of the birds' activities. The first year, eight nestlings fledged from those 10 boxes. Five years later, in 2006, 104 nestling songbirds fledged from his growing trail.

Pauline Tom, a bluebird trail monitor in Mountain City (southwest of Austin) and founder and president of the Texas Bluebird Society, says, "I started talking about bluebirds to my family and friends after I read (and reread) Dr. Lawrence Zeleny's article in National Geographic in 1977. For many years I thought eastern bluebirds only nested in the east. I knew of no one in Texas with bluebirds. I managed for bluebirds for years before I saw a bluebird on my property." She installed a small bluebird trail in Mountain City – including neighboring gardens, church parking lots and other sites that seemed bluebird-friendly. When she started the project, the only bluebirds she had seen were a pair 45 miles away and one lone bird 5 miles away.

At Bluebird Hill Bed and Breakfast near Utopia, LeAnn Sharp says she inherited her affection for bluebirds from her parents. "Since bluebirds had been such a big part of the ranch and my parents' lives, I wanted the trail to continue. If the bluebird trail was going to survive, we would have to take over," she says. Having a history of bluebirds on the property, Sharp was looking only for advice on how to manage the trail when she became involved with the Texas Bluebird Society. "What luck, to find an organization to help us make nest boxes better suited to our climate."

And the climate is a big factor when it comes to bluebird nests. A 6-inch square, 14-inch deep box sitting in the hot Texas sun can quickly overheat, devastating a clutch of precious blue eggs. When she took over her father's trail, Sharp replaced the old boxes with new cedar boxes with a 4-inch overhang around the roof – creating shade for the birds. All successful Texas bluebird trails use boxes that help dissipate the scorching heat. David Shield, who lives in the Dallas area, has made a name for himself with his "heat shield" boxes – essentially a box in a box, which allows for a layer of air insulation around the birds.

"Contrary to pictures on greeting cards, bluebirds do not build nests on a tree branch. Rather, they need a hole," says Tom. But selecting the right setting is critical. Hanan says, "Make sure that the bluebirds have access to open grassy areas that have not been sprayed for insects since that is where they will hunt for food." Bluebird boxes are best set around the edge of large openings over short grass.

To facilitate this, Hanan began a pattern of controlled burning as part of his songbird habitat restoration. "I am sure the combination of nest boxes and brush management has had a significant impact on the number of songbirds on the property," says Len Polasek. At the time, Polasek was the regulatory biologist for Bastrop County, and he says, "The numbers speak for themselves. Fledging 104 young on the property last year has got to have an impact."

Easy access to water is another critical factor. In an environment where the temperature hovers above 90 degrees for months, a place to cool off and refresh is particularly significant. Running water from a fountain, dripper or stream is best for bluebirds since it is fresh and the sound of the water tends to attract them.

The third basic element of any wildlife habitat, after shelter and water, is food. Locating the nest boxes near a large open field of short to medium height grasses allows the bluebirds to hunt their favored food, flying insects, with ease. In the winter, though, insect numbers are low at a time when our bluebird numbers are increasing due to an influx of migrants. Some birds are mistakenly lumped into categories such as insect eaters, fruit eaters or nectar specialists, but seldom is the diet of these animals that specialized – and bluebirds are no exception.

During the winter months, and at other times of low insect numbers, bluebirds will switch to convenient fruit for nourishment. Berry-producing shrubs like yaupon, American beautyberry and pigeonberry help create an environment that will support the birds through the lean times. These sunlight-dependent shrubs normally occupy a transition zone between a clearing and a forested area. They will be most effective if placed on the edge of large, grassy areas.

Creating the habitat is an important part of effective management for bluebirds. Effective record keeping is another. Most successful bluebird trail managers follow a similar pattern of record keeping that allows them to observe and manage changes with the habitat. Once a nest box is occupied, they begin monitoring it twice weekly, opening the box to observe any updated events (beginning of nesting, eggs, young, fledging, etc.). Such updates are noted and the records are kept both for their own use and to share with others through organizations like the Texas Bluebird Society. Monitoring the boxes also allows for control of the non-native and aggressive house sparrow.

While it may sound like a lot of work, enthusiasts say they reap the rewards every time they see a flash of blue and hear the bluebird's cheerful song.

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