Adult gannets are large and bright white with black wingtips. They are distinctively shaped with a long neck and long pointed beak, long pointed tail, and long pointed wings. At sea they flap and then glide low over the water, often travelling in small groups. They feed by flying high and circling before plunging into the sea. They breed in significant numbers at only a few localities and so is an Amber List species.
Gannets do not breed in Scilly; they are present all year round however as they travel huge distances every day for food.  The nearest Gannet colony to Scilly is Les Etacs off Alderney in the Channel Islands, so we presume that Scilly gannets are in fact from Alderney, at least those seen in the summer.

With thanks to Joe Pender for the above photo