Bat House Forum

[Terry Lobdell]

I stopped by to check this box on 6/22/08 and the ground was covered with guano underneath........I'm guessing a good 100 little browns are using it. I got an exit count of 92 bats after pups were flying last year. I mounted it in June of 2005 and later excluded the bats in late August of that year. No observed usage until 2007. It is a few yards away from the 2nd largest natural lake in PA. Judging by the guano underneath I am going to have a higher exit count this year!

[Terry Lobdell]

Here is a closer view........the box has 3 crevices approx. 22" wide and maybe 24" high. The baffles are one inch white pine boards saw kerfed about every half inch.

It is vented on the sides with the back crevice having the most venting to provide a cooler roosting option. The back crevice also has an opening all the way across which helps ventilate and provides another entrance/exit point.

The box is mounted on one inch boards which hold it out away from the building to help reduce guano splatter and allow space for the back vent/access.

The front and sides are covered with aluminum painted flat black for low maintenance. It faces south.

When I stopped today to look there were maybe 10 or 15 bats roosting behind between the box and the log siding.

 

 

[IowaNate]

Just given the approximate measurements of the house it should be able to hold about 400 little browns. Being so close to the lake and the fact that it is finally occupied I bet you will get close to that number within the next few years Terry. I am very surprised though that it took almost two seasons for it to be occupied. Just when we think bats can be fairly predictable, they go and surprise us with something.

  You've got me wanting to see Pennsylvania for myself with some of your great photographs. Perhaps a short vacation might be in order for me!

[Terry Lobdell]

Nate, I was suprised it took that long also........but then it was consistent with little browns in this area seeming to prefer pole mounted bat houses. Which is strange considering there were 50-60 in the attic according to the cottage owner.

If you are ever in the area, I could give you a lot of nice lumber at no charge to build more bat houses. I have a lot of ideas about things I want to try but limited time to do actual projects. That was one reason I donated lumber to the game commission for the condo........

We are going to build another condo next year at a nearby state gameland and now the DCNR is talking about building one at Oil Creek State Park too. I was hoping to get some high school or college students interested in building/monitoring bat houses but have yet to find anyone interested. But hopefully in time I will.

The nice thing about the internet is we can all network together........I would have had no where near the success with my bat houses without advice from Kent, Joe you and others on here.......

[IowaNate]

 I agree about the internet letting us share ideas and experiements more freely. My slanted baffle/standard house and wrap-around chamber nursery house wouldn't  even have been an idea in my mind without you and all the great people on this forum. And to think, I wouldn't be a member or have found this site at all if it wasn't for hearing big browns chattering in my bat houses in late October of 2007 and getting laid-off for a short period at the same time.

  In my opinion this is the best bat house forum on the internet, and it can only get better with more members and new ideas.

[Terry Lobdell]

Here is a view of the lake I took last winter. I will try to get a better picture soon when I go over to do an exit count. This picture is towards the west.

[Joe Spencer]

A fantastic spot indeed.  Looks like another bat house mounted to the left of the current would be great too!  Terry, do you think the homeowner would welcome another bat house? ;)

[Terry Lobdell]

Joe, possibly..........I've thought about putting one on a pole in his yard, but he doesn't have a very big yard.........some friends of mine not far away from here along the same shoreline are interested in a bat house.........they said they have plenty of sunlight. That may be where I put the 2nd house at........

[Terry Lobdell]

I did an exit count here on 6/27/08. It was hard to get an accurate count because they were really swarming. I'll bet 20 flew back up in after exiting. My estimate was 80 little brown mothers +/- 10.

It was very humid with lots of insects flying. I wonder if that was a factor in all the swarming?

After they left, I shined the light up and there only appeared to be about 20 pups. Would the other pups have been out with the mothers going for a ride? 

[Joe Spencer]

Could be but from what I understand, once July hits most young are approaching weights too heavy for mothers to accomodate them and taxing their fat reserves which would somewhat impact milk production which is paramount.  I also thought I read somewhere that there is another reason baby bats accompany their mothers prior to their first solo flights:  pups which are mature enough may be starting to learn and hone their echolocation skills on the backs of their mothers prior to first flight.  Please don't take the latter for being exact, since I can't remember where I read this on the net but some deep researching may confirm or deny. 

[Terry Lobdell]

Thanks Joe! I would say that these pups were about 1/4 to 1/3 the size of the mothers. I would be interesting to know how often the pups go with the mothers in flight.

[Terry Lobdell]

I did an exit count here July 24th. I counted 108 exit and about 15 were still up in the box when I shined a light up.

Based on other counts in previous years, this was what I expected. I got a count of approx. 80 adults before pups were flying. So I expected around 120 bats total after pups started flying.

Every little brown bat maternity colony I get accurate counts on I have pups numbering half the number of adults. No one has been able to give me an answer on this. All the literature I've read says each little brown mother gives birth to one pup. It seems strange that only half the females would be giving birth.

[cloudman75]

One thing could be that some of last years females had not reached maturity at breeding time. They probably still come with their mothers to the place where they were born. I read this on the internet somewhere from what appeared to be a reliable source. Perhaps you could find the information about when they are ready to have pups. If I run across it I will post it. I don't recall where I read it.

[Erik]

Hi Terry,
For my research on forest bats (tree-dwelling) near my hometown I captured some emerging Daubenton bats (Myotis daubentonii) at a maternity colony. I only captured the first three emerging bats, one nursing female  (swollen and bald nipples) and also two young males (from last year). It seem, and I read that as well, that also immature males can roost in a maternity colony.

Based on the counts so far it seems that of the pipistrelles in my nursery house in Tilburg (Netherlands) only about 30% got pups. But I must admit that I couldn't count for 4 weeks so maybe a part of the colony has already moved to elsewhere.

We like to think of bats using a single roost, but almost all bats use a network of roosts and move every couple of weeks. Even mothers and pups do not necessarily have to to roost in the same bat house. Numbers of bats can go up en down throughout the whole nursery period.

Every year I experience at exit counts that the first bat that shows up is flying into the bat house, so coming from elsewhere. I also once found a big nursery colony of daubenton bats in a woodpecker hole, with three noctule bat pups (Nyctalus noctula) between the daubenton bats pups. There where no adult noctule bats in that tree. At the exit count we observed two noctule bats flying into the tree roost and leaving again after approx 5 minutes.

What I want to say is that there are many factors that influence fluctuations in exit counts. It is very difficult to say how many mothers gave birth to pups.

Erik

[Terry Lobdell]

Erik, Thank you for that information! I too have maternity colonies that move around a lot..........One of my big brown maternities has used 10 different boxes this summer!

I wondered if there was a possibility that some males may be roosting with the mothers........I feel better now..........I was worried that maybe there was a problem with my bats. 

I have had 4 different little brown maternity colonies where the number of pups has been about half the number of adults.

Each year I am involved with bats, I do exit counts more often. In the last 3 years, everytime I am able to get an accurate count, these are the ratios I am getting: Two little brown adults for every pup.

Thanks again!