If you haven’t done so already, check for old nests in bluebird houses (and other nest boxes too). Best to wear gloves for this chore, and dispose of the nest away from the birdhouse as old nests will attract predators. Clean the box with a mild bleach/water solution (1:10). Scrub, rinse well with water, and let dry in the sun.
The NABS reference above? It stands for the North American Bluebird Society, who gives their approval on certain bluebird houses. The houses must meet specific criteria that’s beneficial to hosting successful bluebird broods and fledges. This is elementary stuff for serious blue-birders, but so many of us are novices and we all have to start somewhere! If you’ve been unsuccessful in enticing bluebirds to your yard, there are lots of great suggestions, and some fantastic information at www.sialis.org. We would strongly recommend this well organized and informative site for anyone interested in hosting bluebirds.
Bluebird houses will differ for the Eastern and Mountain/Western Bluebird, although Eastern Bluebirds may use a Mountain Bluebird House. Eastern Blues require a 1-1/2 inch diameter hole, where as Mountain/Western Blues require a 1-9/16 inch entrance. This is where some of NABS Approval comes into play because an entrance that is 1-5/8 inch, will allow Starlings to enter the box, but Starlings can not enter through a 1-9/16 inch hole. Now who would know that? Floor size (4×4 for Eastern Blues, and 5×5 for Western/Mountain Blues) and ventilation are some other criteria for approval by NABS. A predator guard at the entrance of your bluebird house always helps to ensure successful fledges, as does a baffle if the house is pole or post-mounted.
Water, food, and potential nesting spots are key to enticing these fantastic birds! Bluebirds prefer open area for their hunting style (swooping to catch insets), so if your yard is heavily wooded, chance are Bluebirds won’t find it suitable… but other birds will. Chickadees and Nuthatches are already scouting nest boxes and building nests too. We just tried put up one of those side-entry houses supposedly meant for Nuthatches… we’ll see how that goes soon enough.
Spring has sprung early this year, so get in the yard and help local birds thrive!