Looking for food or a new nesting site?

This little wren intermittently checks out the hole in our apple tree. He / she darts in, stays a few seconds and then flies off again. I've tried many times to get a picture and this is the best I have obtained. A bit blurry, but no second chances with this nippy little soul!

It would be fantastic if it nested in there this summer.....but I think that would be too much to hope for!!!

It was this blip or another idea that came to mind today.....but not enough time as I'm busy organising things for our trip to Worcestershire tomorrow