It was really interesting to watch, for a bit, but actually, once you've seen a few birds being ringed and measured, it quickly loses its edge, so after they'd done a couple of nests, we came away. Sadly, I didn't check the photographs I'd taken immediately, something I almost always do, and when I came to download them onto the PC, I found them rather disappointing. This is the least bad of them.
I did expect them to be carrying a parasite load, but had no idea that the lousefly is so big - it's easily 5mm long, and each bird can carry several of them. Revolting!