A DOZEN BLUEBIRDING MYTHS, by E.A. Zimmerman
MYTH: You can put up a nestbox and forget about it.
REALITY: Bluebird boxes should be monitored at weekly during nesting season, to check on progress and control House Sparrows, blow flies, paper wasps, and to remove unhatched eggs, etc. Boxes should be cleaned out after nesting (see next myth). At least annually, you should also replace any split, rotten, or broken pieces on boxes that could let rain in and chill nestlings.
MYTH: Bluebirds will remove old nests from a nestbox.
REALITY: Bluebirds will not typically clean out old nests by themselves. They may build a nest on top of another nest, but this may promote disease and parasite infestation, and may increase the likelihood that a predator will be able to reach in and nab eggs/nestlings that are closer to the entrance hole. The detritus can also attract fire ants. It is best to remove nests as soon as the young fledge (birds in the North begin another clutch an average of 17 days later, in the South 26 days),or if nesting fails (since they may try again in 1-7 days), to encourage another brood. Put nests in the trash to avoid attracting predators. If mice nest in the boxes over the winter, clean the box out before bluebird nesting season starts.
MYTH: If you open the bluebird box, or touch the nest or babies, the parents will abandon the nest.
REALITY: Don’t worry that monitoring will make the parents desert the nest. Bluebirds are quite tolerant of human presence. Touching the nest or birds will not make the birds leave–your mother just told you that to keep you from harassing them.
MYTH: House Sparrows won’t bother bluebirds or their nests.
REALITY: House Sparrows are probably the number one enemy of bluebird. Unlike starlings, they are capable of entering the 1.5″ round hole of a nestbox. You might think they’re cute (some bluebirders refer to them as “rats with wings”),but they will attack and kill adult bluebirds (sometimes trapping them in the nestbox), and destroy eggs and nestlings. House Sparrows are non-native invasive pests not protected by U.S. federal law. House Sparrow nests, eggs, young, and adults may be legally removed or destroyed. It is better to have no box at all than to allow House Sparrows to reproduce in one.
MYTH: If you don’t have problems with predators on the trail the first year, you never will.
REALITY: It may take time for raccoons, cats, and other predators to discover nesting areas. Unless you don’t mind finding broken eggs, abandoned/dead babies, or a pile of blue feathers, install guards to keep predators from raiding nests (e.g., a 2 ft. long, 8″ diameter capped stovepipe or PVC pipe sleeve on the pole, mounted loosely just under the box).
MYTH: If you don’t get bluebirds in your nestbox/trail the first year, you never will.
REALITY: It may take several years for bluebirds to find your nestboxes and choose to use them. Don’t get discouraged if bluebirds don’t nest in your boxes the first year. In the meantime, your nestbox can provide a home for other delightful, cavity-nesting native birds, such as Tree Swallows, chickadees, and titmice.
MYTH: It’s too late in the year to install a nestbox because bluebirds have already started laying eggs.
REALITY: It’s never too late to install a nestbox. In some areas, bluebirds will raise two to three broods. If a nesting attempt fails, they may move to another box. Bluebirds and other birds like downy woodpeckers may also roost in nestboxes during the winter.
MYTH: Bluebirds prefer to nest in boxes mounted at eye-level.
REALITY: Eye-level is convenient placement for human monitors. Bluebirds will nest in, and may even prefer, boxes that are 8-20 feet off the ground. However, it is perfectly fine to mount a box at eyelevel (as long as you use a predator guard) – it won’t deter bluebirds, and will facilitate routine monitoring.
MYTH: You should collect earthworms and put them in a feeder for bluebirds.
REALITY: Bluebirds love mealworms, but should not be fed earthworms. The baby birds’ undeveloped stomachs apparently can’t handle earthworms because of the dirt castings in the worms’ gut. Eating earthworms (sometimes used as a source of food by bluebird parents during bad weather, when little else is available) can cause severe diarrhea, which can result in dehydration and starvation. Also, bluebirds rarely, if ever eat, bird seed – ~68% of their diet is made up of insects: grasshoppers, crickets, beetles, spiders, and caterpillars. They also like fruit from plants like flowering dogwood, holly, mulberry, wild grape, Virginia creeper, pokeweed, and viburnum.
MYTH: Plexiglas roofs / holes in the roof/extra light in boxes will keep House Sparrows out of boxes.
REALITY: Unfortunately, this is not so. A change may deter House Sparrows temporarily, but they will nest in these boxes, and in gourds suspended on wires, evergreens, barn rafters, etc. An open-topped box (Bauldry) is no longer recommended due to concerns about wet nests and hypothermia. A box with a Plexiglas on top can fry contents.
MYTH: Bluebirds were on the brink of extinction, but now they are back and don’t need your help anymore.
REALITY: Bluebird populations declined by an estimated 90% from1920-1970, threatened by competition from introduced species(House Sparrows and starlings), loss of open space and nesting cavities (bluebirds can’t excavate their own holes), increased pesticide use, and climatic events. While Eastern Bluebird populations are now increasing (probably due to conservation efforts), Western Bluebird populations are not. And none of the issues that caused the decline has really gone away. Without assistance from people like you, bluebirds will continue to have difficulty surviving and thriving.
MYTH: Bluebirds behave the same way, all the time, everywhere.
REALITY: Eastern, Mountain, and Western Bluebirds in different areas behave differently and show different preferences. Even the same birds may behave differently as they age; as seasons, climate, and conditions change; and from one year to the next. Some people who aren’t following any of the “rules” still successfully fledge amazing numbers of bluebirds year after year. Avoid “never” and “always” and do whatever works in your area!
Special thanks to the members of the Bluebird_L for their help in compiling this list.
Note: An August 2004 version of this article was printed in the NABS Bluebird Journal Fall 2004, Vol.26, No.4