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Caring for Bluebird Nesting Boxes

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By Tommy McCarthy, Environmental Educator

This year WNC installed two new bluebird nesting boxes as part of a grant from the Connecticut Ornithological Society! We had a pair of bluebirds successfully raise young in one, and tree swallows in another. As the nesting season comes to a close, we thought we would share our tips for anyone who owns a nesting box currently or is interested in setting one up for next year! Since the beginning of fall marks the end of the breeding season, I’ll speak first about how to reset used nesting boxes for the winter, and afterwards get into how to install new nesting boxes before spring. Lastly, I’ll share some species you might expect to see using your boxes and go over how to safely and respectfully monitor activity!


The end of the breeding season is here, and each of our bluebird boxes ended up providing a home for nesting pairs, it’s time to clean them out! Late September - November is the ideal time to do this This process is fairly simple, and consists of removing the nest and thoroughly rinsing the box out with a hose so that no droppings or insects remain. Scrubbing the inside of debris with gloves and water is also fine if you can’t take the house down to hose it off. One insect that sometimes is found are blowflies, which parasitize bird nests by laying their eggs in nesting material. After blowfly eggs hatch, their larvae attach themselves to nestlings to feed on their blood. They usually don't cause major issues for the birds, but in combination with other stressors they can cause broods to fail, so it’s important to give the box a thorough rinse at the end of the season to ensure that none remain. Once your box is clean and dry, you can winterize it. Bluebirds and other cavity nesters sometimes huddle up to sleep in boxes when the weather gets cold, and small mammals may also use them to hibernate if they can reach them. You can make your box suitable for this by preparing a cozy, clean nest of your own using dried grass; and using weather stripping to seal the gaps and cracks that are there to provide ventilation in the hotter months. Once all this is done, you can leave your box as is during the winter.

Once February rolls around and birds are preparing for spring, it is time to prepare your box for any prospective nesters! Eastern Bluebirds in Connecticut stick around through the winter, and will typically start building nests sometime during March. De-winterizing in February is important in order to make sure you don’t disturb birds by doing it after they have already chosen your box as a nesting site. All you need to do is remove any materials you may have added to insulate the box, check it for use, and clean out again with a hose if it seems like it was used. Once again, you can add a bed of dry grasses to provide a soft base when you remount it. If you are mounting your box for the first time or reconsidering the location, keep in mind that Eastern Bluebirds prefer semi-open areas like meadows or mowed grass with sparse trees. They usually hunt for insects from a perch, watching for movement and swooping down to the ground to pick them up - so make sure there’s something nearby they can use as a perch like a low tree branch, a snag, or a fence! It’s also ideal to have your nesting box facing south so that sunlight warms the entrance through most of the day. 


During the breeding season, typically March through August, monitoring your bird box for activity can be exciting and educational! You can learn a lot about birds just by watching them go about their business. Once you have a pair using your box and you’ve seen them collecting nesting material, you can start to check the box for eggs on a weekly basis. Be sure to minimize your presence as much as possible when approaching the box. It’s best to check when you know there is no bird currently inside, but sometimes it’s not possible to be sure. Before opening, you can gently tap on the side of the box and they will probably fly out to a nearby branch. Once you see eggs, you can look forward to observing new behaviors and future fledglings, but it is important to stop opening the box as the birds should be left to care for their brood without disturbance. 


Once again, nesting boxes are a great way to improve habitat for birds and learn a lot about them in the process! At Woodcock, we are looking forward to another year of caring for our new boxes and observing the charming little critters that use them. We hope all these tips help any current or prospective nesting box owners!

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