It was fortunate that the first two nest boxes I checked didn’t have any animals in them. Today I did the preseason check of 4 pairs of bluebird nest boxes for the DuPage County Forest Preserve that I’m tasked with monitoring to encourage bluebird nesting this season. (Learn more here: bluebird monitors.) The first box had slid down it’s post and was leaning at a 45 degree angle. I repositioned it and then opened it to clean it. It was empty. The second nest box was also leaning a bit, so I repositioned it, too, and then opened it. I cleaned out the remnants of last seasons’ tree swallow nest and prepared it for a new nest. This is when it occurred to me that maybe I should check inside the box before I learn against it and hoist it out of the ground. I walked around the side of the next box and saw a field mouse peering at me through a ventilation hole! I carefully opened the front of the box to reveal the mouse atop his nest of grass. I told him he needed to find another place to live and moved on to the next pair of boxes. I thought I’d come back to this one when I was done to see if the mouse, now so exposed, had taken advantage of the opportunity to leave on his own.
I gently knocked on the next box. No nose appeared in the ventilation hole, so I opened the box. There was a big nest of grass inside, which I grabbed to remove and clean the box. Three field mice came flying out of the box with it! Startled, I quickly dropped my handful of grass. Apparently, they were hiding under their grassy nest, not on top of it as the bold first mouse had been. Two if them hit the ground and disappeared. The third one clung to a sapling that it landed on in front of the box. After I took a picture and stepped back, it promptly ran back into the empty box. A new strategy is in order. I left this box, and 4 of the next 5 nest boxes which also had three mice each, open. I removed most of their nesting material and left them fairly exposed, crouched in the back of the boxes.
I hope they take advantage of their time over the next few days to find a more suitable home. I will be back next week to clean and close up the boxes and I’d rather not have to evict them.