A couple of the sites are quite new to the project, so it wasn't surprising they weren't occupied, but three sites we'd expect to be occupied were empty. There were also two sites with birds present but not breeding, so this does seem quite a high number.
This did leave several sites with birds in residence, but even some of these sites had new, unringed birds present. In fact we ringed nine birds at six sites, with just one recapture and even this was a bird ringed as a chick nearby the previous year. So although many of these birds had clutches of five or six eggs it may be that many new birds have been recruited, so it'll be interesting to see how the season progresses.