I watched one morning as over a dozen blue tits emerged from one of our nest boxes. They also go looking for spiders etc. in them.
In an ideal world I would leave the tops on perennials over Winter, but as it takes from now until Spring to clear them all off that is not a choice.
By the way what do you folks do with the removed top growth? A lot of the stuff we have will not rot and believe me I have tried. It is very difficult to shred, except when very dry and ditto for burning. Be nice to be able to put it in the Council compost bin, but I filled both of ours witrh the Clematis I cut down. Only another 60 or so of those to do too.