WHITE- BILLED DIVER

There’s actually a fourth diver species to be seen in the UK, and we’re learning more about it all the time.

The White-billed Diver (also known as the Yellow-billed Loon on the other side of the Atlantic), is the largest member of the family, and breeds in Russia, Canada and the USA, generally wintering in the north Pacific and off north-west Norway.

It was only identified as a species in the early 19th Century, as it looks very similar to the Great Northern Diver, especially in breeding plumage (the bird in the photograph above is a juvenile), the main differences being the invariably very pale bill, held above the horizontal, and a slightly larger, chunkier build. In its winter plumages, the White-billed Diver’s upperparts also appear darker.

It was previously thought to be a rare vagrant to the UK, and indeed may well have been, with just 39 British records by 1973, most of them post-World War II. Most birds were seen in winter or early spring, and were thought to have drifted south from the population wintering off Norway.

In the early 2000s, though, two discoveries were made. One (as a result of a Red-throated Diver survey) was that significant numbers of White-billeds were present off Lewis and Harris, in the Outer Hebrides, in spring, where they moult on their way back to Russia.

The other was that small groups were also appearing in spring in the Moray Firth, especially off Portsoy, Aberdeenshire, generally being further out from shore and in deeper waters than Great Northerns (which is where the White-billed’s heavier build comes in).

Their partial moult is generally completed by mid-April, after which the birds continue north and east to their breeding areas.

But questions remain. For one thing, had the White-billeds always been using UK waters in such numbers, and remaining unnoticed, perhaps because of that habit of using deeper waters not easily watched by birders? Or have their habits changed, perhaps in response to food availability, climate change, or linked factors such as these?

Perhaps more excitingly, are there any other spring ‘staging’ areas still to be found? It’s possible, if not necessarily likely. And where do these spring birds spend their winters? Again, there are exciting discoveries waiting to be made.

The lesson for us birders? Take a very long, hard look at every Great Northern Diver you see (as if you wouldn’t anyway), just in case…