The Neighbors Upstairs...

I've been learning an awful lot about bats over the past couple of weeks.  I have a sneaking suspicion that my attic has turned into a maternal roost this year, and I have to admit that I'm not too excited to have neighbors upstairs.  I'd like to encourage them to leave on good terms, though, for two reasons. The first is simply that bats are pretty darn cool and are incredibly beneficial to the ecosystem.  The second is more serious- little brown bats may soon be added to the Federal endangered species list due to concern about white-nose syndrome, a fungus which has killed over a million bats in the eastern United States over the past four or five years.  (White-nose syndrome was confirmed in Maine earlier this year; previously, the state appeared to be fending it off better than other New England states.)  The little guys need as much help as they can get.

So I did a little research and purchased a bat house from the Organization for Bat Conservation. The house is basically a box that's open on the bottom and has two baffles inside to create three vertical nesting chambers.  This particular house claims to handle 300 bats, which is hopefully enough.  (BCI also makes a 500-bat version, which we may look at next year.)  They're pretty easy to make, but with all of the activity we have going on this year, I figured it would be easier to purchase a finished house instead.

Once we stain it a dark walnut or black (to keep things warm the weather turns cold), we'll mount it on the south-facing wall of the workshop.  Then comes the fun part: we somehow have to convince the bats to move out of our house and into their house.  That's when we add some caulk, PVC pipe, duct tape, and clear plastic to the equation.

Getting bats to move out of your house is (apparently) most easily done by excluding them from the house altogether. That means sealing off any entrance bats could use.  That means sealing off any hole or crack greater than 3/8ths of an inch. Bring on the caulk.

Unfortunately, if you seal off every entrance point, you'll probably seal some bats in instead of out.  Cue the PVC, duct tape, and plastic.  Bats initiate flight by dropping from a height and swooping.  When they come home to roost, they swoop below the opening and crawl inside.  What we need, then, is a one-way door that they can swoop out of but can't crawl back into.  (A bat check-valve, if you would.)  A PVC elbow plus a short length of pipe aimed downward works great for this because bats can drop from it as they're used to, but it's slick enough that they can't find any purchase for crawling back inside again.  Extending the PVC with a tube of clear plastic makes the door even more effective.

So that's my bat story for today.  It'll be interesting to see how all of this research actually works in practice.  I do know that it's nearly impossible to seal all of the cracks in a house in the woods, so hopefully the bat house is enticing!

More bat information can be found at Bat Conservation International.