Rain

Here's a rain effect on bat emergence. Compare this graph with the one from 5/16, posted below.

It started raining hard here last night, just around sunset. You can see the temperature drop during the rain, and then level off again afterward. Notice the peak in calls when the bats first emerge. Usually it is around 8:00 PM, just when it's starting to get dark. But, and I'm presuming this is because of the rain, the big peak in calls signifying leaving the bat house is delayed until about 10:00 PM, after the rain lets up.

This coincides with what I heard in listening for the counter that tracks bats emerging from, or entering into the bat house. No counts until about 10, but then almost 200 transitions during the rest of the evening. It seems the bats got a late start because of the rain, but made up for it with a really active night later. Rain probably means more insects for food, too.

In future posts I'll talk about how I count the bats entering and leaving the bat house, and show some data about how this indicator of activity changes over time.