With bluebirds now nesting across the state, I am often asked, “Should I check my bluebird boxes?” When this question is posed I always tell folks that, if it done properly, checking bluebird nesting boxes can actually be beneficial to the birds. Let me explain.
Unlike many birds, the eastern bluebird is more tolerant of human activity around their nests than many other birds. This tolerance allows the close monitoring of the success of the birds’ nesting efforts. By so doing we can help thwart situations that can lead to the failure of a nesting attempt.
For example, we can keep house sparrows from taking over a box by tossing out the sparrow’s bulky nesting materials. If this is done enough times, the aggressive, unprotected, invasive house sparrows will finally give up and leave the box alone.
(Never remove the nest of a native cavity-nesting bird.)
Also, wasps will occasionally attempt to build a nest on the underside of the top of a box. If wasps are allowed to build a nest inside a box, bluebirds will abandon it. With that in mind, if you find a small wasp nest, remove it.
If you plan to monitor a box, make sure the box can be easily opened. Too often boxes are made in such a way that the box cannot be opened from the top or side.
Make every effort to make nest box checks as brief as possible. In addition, it is always best to check boxes when temperatures are mild, winds are calm, and it is not raining.
Checks can be safely performed weekly up until the hatchlings are 12 or 13 days old. Checks made after that time can result in the youngsters prematurely bailing out of their nests.
If you monitor you boxes on a weekly basis, you will know when a nest is built, when a female lays all of her eggs (females lay one egg a day until the clutch is complete), incubation has begun, the approximate age of the hatchlings, and how many young bluebirds successfully fledge.
Here are some facts that will help you understand what you will be observing. Typical clutch size is 4-5 eggs; Incubation lasts 12-14 days; Time of fledging: anywhere from 17-21 days.
The North American Bluebird Society recommends the nest be removed after the young fledge. If a bluebird wants to use the box later, a new nest will be constructed in short order.
However, dispose of the old nesting materials some distance from the nest site. This will help keep potential predators from discovering the location of the nest.
Keep in mind, eastern bluebirds will nest up the three times a year.
If you have additional questions about checking, please let me know.