Bat Invasion

In 3 years, I have found just 2 bats in bluebird nest boxes. During this (not yet finished) 2015 season, I have recorded 6 bats in 13 days. Five boxes in 3 different areas were used by these roosting bats that always choose the door (of the 3 non-holed walls) to hang on. All chosen nest boxes but one were located on the edge of a wooded area and within 100 m of a pond.

Without gloves and a permit to band and measure these bats, I am unable to tell if the same individual has been caught more than once, and I also cannot identify the species. Every time, it was either an evening bat or big brown bat. These species look very much alike. The only difference is that big brown bats are bigger than evening bats.

Below are pictures of 4 of the 6 observations