I’ve just been told this is a common diving petrel (thanks Stu) so there we are, mystery solved. I’d thought it was a storm petrel because of its size but its markings didn’t seem to fit. It turned up yesterday when I spent the morning giving a walk/talk at Shakespear Park to a great group of kids from Monte Cecilia school. As always kids find things and while investigating a “log shark” on the beach someone found this dead petrel. This birds back is all black, the tail is forked and the legs a powder blue.The feather colouring didn’t seem to fit the white-faced (which is the common storm petrel of the area) or any other storm petrel in the field guide. Because its feathers are waterlogged I thought I was just missing something but it turns out I was just wrong. Thanks Monte Cecilia for your interesting find.