Today a visit to the top floor revealed that both Black-headed Gulls Chroicocephalus ridibundus and Common terns Sterna hirundo have large young. A small number of Black-headed gull chicks has fledged by now (I ran into one in the street below a couple of days ago). The solar panels seem to provide a useful shelter to the chicks. The Herring gull pair from the previous post (no solar panels present) lost all its chicks shortly after hatching.
