Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters


Bats in Bluebird Nestboxes

Bat in nestbox. Photo by Bet Zimmerman.

Female bats may use bat houses to raise and shelter their young. Male bats do not live in colonies - they sleep singly in trees, etc. If you find a bat in your nestbox, it is very likely a young, inexperienced male. It is not living in the nestbox, it is just temporarily sheltering there. A fair number of bats will borrow bluebird boxes for a nap either early or late in the season. It will probably be gone the next time you check the box.

  • I found this small bat on the right in a Peterson box in August 2008 in CT. Note shiny black fecal material shaped like rice on floor. From the photo, Jenny Dickson of the CT DEP thinks this is a Big Brown Bat (Eptesicus fuscus). The rich, chesnut brown fur and bare muzzle are two keys.
  • A woman in South Central Indiana found a bat in a NABS style box with a round (1.5") hole, gabled roof, rough cedar, on a pole with a stovepipe baffle. She said Tree Swallows were interested in the box, and then went away and she thought it might have paper wasps. When she opened it up a brown fuzzy bat dropped to the floor. (She closed it up and let it be, and plans to put up a bathouse.)
  • Bob Peak of Henderson, KY reports that on trails at Land Between the Lakes (western KY/TN-165 nest boxes in a 170,000-acre National Recreation Area), they usually have at least one bat occupancy per year. It’s usually in the same area, and it’s usually a single bat. (However, they have had at least two or three together in the same box.) The species is unknown. They have shown up after birds have fledged, or in an empty nest box, so there is no nesting interference. They allow the bats to remain in the box, and, on the occasions when they ’ve checked, they are gone the next day.

As a first-time bluebird monitor, I am alternately mesmerized, mystified, and petrified. Until now, I never gave much thought about how the day-to-day existence of wildlife is so perilous and fragile. What an education!
- Donna Spray, Bluebird_L, 2006

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Photo in header by Wendell Long.
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Last updated March 24, 2016. Design by Chimalis.