Bat House Forum

[Rick]

Around the first 2 weeks of April ,I noticed lots of bat activity around my nieghborhood. Just as it got dark they would appear. Little browns and Big browns. I would see them for at least an hour then nothing or very little activity. about a month later first 2 weeks of May, all of a sudden I dont notice them anymore. I see one here and there come evening but not like it was the month of April. I did notice more bats with favorable weather. Im just wondering whats with this? I suspect their absence had to do with them giving birth and not venturing far from their colony.I also suspect it may be a availability of prey issue. I live in the western suburbs of Chicago in a wetland area. Any thoughts on this behavior would be appreciated.

[LarryH]

I don't think it is unusual for the bats to move around to different roosting places, unless they have pups that they are taking care of.  There was an excellent article on this in the BCI magazine a few months ago, where they did research on the roosting habits of bats. They found that they moved frequently, but always seemed to stay with the same group as they moved.

I've noticed the same thing, but to a lesser extent.  The bats arrived about 2 weeks earlier this spring, and arrived in heavier numbers.  Then, in mid-May I noticed that there were about half as many as there were in April.  But, when they started having their pups in the first couple weeks of June, the population was back up about what it was in April.  I watched them emerge last evening, and there were even more of them than there were in April. 

One thing that has been concerning me this year, is the heavy rain season we have had.  We've had rain nightly for several weeks and I'm not sure how the bats can fly enough to get the insects they need.  Every week when I mow, I check for guano under the bat houses, and the amount increases every week.  So, they must be eating.  And, I haven't seen a mosquito yet this year.

[Terry Lobdell]

My bats move around a lot also. Seems like they roost in one spot for about 3 days then move. I've been keeping notes in a journal to see if there is a correlation with weather conditions but so far I see no pattern. Last week I had 29 little browns exit one of my houses that faces north. The high temp. that day had only been 75 degrees. I would have thought they would have chosen a south facing house on such a mild day.

I've had very rainy weather here in nw pa as well. My bats seem to exit earlier, maybe to get some feeding in before it starts to rain again.