We've had some swifts nesting firstly in the eaves and now slightly further into the loft (I presume they've used some of the membrane as nesting material and made the hole larger), plus some sparrows I think at another point.
What time of year is a good time to repair / block these holes so as not to interfere with nesting? And how thorough should I be about cleaning up behind them?
Cheers!
Matt