I have had little Brown bats living in my house wall behind the brick chimney for at least three years. The location is southeastern pennsylvania, 20 miles north of Philadelphia Pa. (USA)
At dusk, observing the two holes in use, I counted 70 bats last year, I counted 157 bats on July 15 2008, I was going to attempt a count two nights ago, and was surprised to see only one bat. I am disappointed that the bats have completely left my area, I can't even see any flying tonight. The living space may be filled with guano now, and I imagine the colony has found a better site. Is this a sound theory? Should I attempt to erect some Bat houses to get them back? I will miss them if they have moved far away. Should I investigate the hole and see if they died or were trapped inside somehow??? It was a drastic change, a large colony just disappeared on me, and aren't even flying in this neighborhood tonight.
Don't worry! Little brown pups have just recently started flying and the whole colonies will just up and leave. The mothers teach them how to hunt and they explore other roosts. From my observations, their behavior seems very much like birds after the young have fledged. They might come back this summer and they might not. Or a few may come back. I am very certain they will be back behind your chimney next year early in April.
You are a little bit south of me, so your bats may have been born earlier, and therefore your colony may head south earlier.
This year my little browns started flying on about July 20th. Counting pups and mothers I had about 70 - 80. I went down to count another colony about 2 miles away at my cousins and strangely his colony had grown by about 70 - 80! I went back up to my house and sure enough..........my entire maternity colony was gone! I'm about 90% sure they were the same bats.
They were gone about a week and then came back. I did a count 2 nights ago and there were only 38. This is typical of other years. My little brown bat maternity colonies seem to break up and disperse starting in early August.
You should have a few little brown bachelors into October. Keep us posted on when they come back!
