Bluebird numbers in the eastern United States have decreased 90 percent in the last 60 years. There are several reasons for this decline:
• Food supply: In the landscapes and around the garden, bluebirds munch on grasshoppers, flying insects, beetles, caterpillars and other insects. Widespread use of broad spectrum insecticides has targeted many of these insects depleting the Eastern Bluebirds’ food supply. (They also eat berries and fruits found near their nests, especially during the winter when insects are scarce.)
• Climate: The bluebird population is usually pretty stable in winter. However, Eastern Bluebirds cannot tolerate severely cold weather, which increase their mortality rate.
• Nesting places: Our agricultural practices affect the population as well. In our landscape maintenance, we often prune or remove trees with open cavities — a perfect place for bluebirds to nest. Like the robin, bluebirds prefer open areas with little or no groundcover. Eastern Bluebirds are spotted in orchards, open woodlands, clear-cuts, parks, and in suburban and rural areas roadsides. Non-native species of birds like the House Sparrow and European Starling come in and compete with Eastern Bluebirds for nesting sites in these areas making it even more difficult for them to find a home.
Bluebirds in Alabama may produce two to three broods a year. The female begins the first nest in mid-April, then lays one light-blue egg per day for 4 to 6 days incubating the eggs for about 12 days.
About 15 days later the young Eastern Bluebirds start to leave the nest. Juvenile bluebirds have a gray back and spotted white breast, with only a hint of blue on their wings and tail, not the rust-colored breast and blue back and tail that we see on adults.
The male is in charge of the young birds, feeding them and teaching them how to feed themselves, and continues to do so days after they have leave the nest.
While it may look like the male bluebird is doing all the work, the female is no lazy bird. She immediately starts cleaning up and remodeling the nest for yet another brood.
Lucky for us, bluebirds will use manmade nesting cavities or boxes. The boxes are not difficult to make. The Alabama Cooperative Extension System has a set of box plans available online at www.aces.edu — search “Eastern Bluebirds, ANR 687.” Or drop by the local county extension office and pick up a copy.
Nesting boxes should not be made from treated wood. You may wish to paint the outside of the box with a light colored paint. It is important to make the houses, including entrance holes, the correct size. You may notice the plans do not have a perch. That’s because Eastern Bluebirds do not need a perch, which otherwise might invite other species such as sparrows.
Nesting boxes should be up no later than the end of February. Look for areas with open fields or pastures where insects will be plentiful, and place boxes 4 to 6 feet above the ground and 50 to 100 yards apart. If possible face the boxes south or southeast. Try to select places where trees, shrubs, utility wires or fences are within 25 to 100 feet of the boxes. This will provide a perch for bluebirds to feed and will eventually help the young fledglings in flight.
Starting in early March, check the boxes once a week and continue to do so until July. To check a box, carefully open it up and look for signs of nesting or eggs. You can even have a little fun and record this data each year to keep up with populations in your area. In late summer, after the brood has left, clean out the old nest material so re-nesting can occur.