Walking across Higher Hodder Bridge, I noticed a lot of activity from Blue Tits, and it soon became obvious that they were going into nests built inside cracks in the bridge itself. I thought at the time that what they had in their beaks was nesting material, which struck me as a bit odd, as they should have finished their nests a few weeks ago. It wasn't until I could look at the photographs back home that it was obvious that the blue tits had caught flies that they were feeding to their young.
