I used to think that things around the bat house fell into a simple pattern — drop down and fly off at dusk, chase some bugs all night, and then swoop back into the bat house just before dawn. I soon found out this view of the bat life was way too simple.
This particular video shows a peak time for activity around the bat house, just before dawn. Rather than straggling in one-by-one and disappearing quickly into the bat house, these bats like to circle around, en masse for a while. Notice all the times when an individual almost disappears into the bat house, but then quickly turns and buzzes off. In a few minutes, when it gets a bit lighter everyone will eventually land and enter, and things will be quiet, except for a few squeaks and chirps.
Looking at the data from the various sensors along the bat house entrance I could see that bats were coming and going not just near dusk and dawn, but on and off during the night. A typical evening might have the bats leaving around 8:30, with everything quiet until maybe 10:30, when all of a sudden, bats swooping in and out once again. Then quiet, then maybe a burst of activity around midnight, and so on until, near dawn, maybe 6:30, a whole lot of buzzing, touch-and-goes, and finally quiet as the Sun came up.
As you can see from some of the other posts here, I got really interested in capturing images of these bats during their nighttime routines. With the plummeting prices of video cameras intended for the security market, I was able to put up a camera to watch the area around the bat house 24 by 7.
Actually, I found this rather neat camera from SuperCircuits. It’s color in the daytime, not that there’s much to see around the bat house then. And at night it switches to monochrome and turns on a built-in Near Infra-red illuminator. That yields bright night time images in a light that we mammals, including bats, can’t normally see.
The camera says it’s weather resistant, but that’s assuming it under some sort of over-hang. So I built a little wooden roof attached the camera to it, and put the whole assembly up on a pole higher than the bat house.
Here’s the camera, on its side as it’s being installed in the cover. Note my attempts at camouflage paint on the box – since the camera will be on a pole in a tree, might as well try a little subtlety for the benefit of the neighbors. The lens is in the center of the circular array of IR LEDs that supply the illumination once night falls.
A closeup of the camera installed on the pole, and extended into the tree beside the bat house.
Actually, the corny-looking camo doesn’t do too badly in making the camera at least a little less obtrusive. Here it is from a distance:
This video at the top of this post was shot using this camera, and another little monochrome camera mounted at the base of the bat house. Both shots, the one from atop the pole camera and the one looking up at the opening of the bat house are illuminated by the Infra-Red LEDs on the pole camera. Invisible to both the bats and us, they provide plenty of light for these scenes.
Hopefully the video clip provides a feel for just how fast these creatures are. Although they look like bright blurs in the video from the pole camera, that’s an IR effect and they’re basically dark brown, almost black in visible light. Maybe this is why lots of folks have never even noticed that bats probably fly over their backyard every night – it’s dark, they’re dark, and they’re passing by really quickly.