An all-white gannet looks so weird. I googled this, because I didn't realise that Northern Gannets only get the yellow head while in breeding plumage - there are very few photos of all-white gannets on Google Images so I'm guessing they are mostly photographed around breeding colonies. The Cape and Australasian Gannets have yellow heads all year round.
I know what you mean about the all white being unusual, and must admit that I didn’t know the fact about the yellow head either. We are off to see them at one of their breeding colonies in the UK (Bempton Cliffs) at the end of May, so will expect them all to have the normal yellow head I guess?
Like most European seabirds, gannets spend the winter at sea, so they are much harder to see than they are at nesting time. Most records are from the western Atlantic, including the Bay of Biscay and off the coast of the Iberian peninsula. Some reach the coast of West Africa and the western Mediterranean.