Page 19 - Out Birding Issue 111 Summer 2023

been seen in the UK in a single place at one 􏰀me and soon got the birding communi- ty excited. Many of these birds were at the edge of viewing range for our telescopes, so we organised two boat trips to try to see how many we thought were there. I ended up organising the first of these and we amassed evidence for there being at least 13 different individuals in this flock, the second trip managed to up this to 15 for their trip. There were likely to be many more in the waters we were unable to visit.
These birds have been turning up here and nearby off Burghead Harbour for several years now each spring, first appearing in March and disappearing by mid-May. When they first appear at the start of their stay, they are in their rela􏰀vely drab winter plumage, but the latest stragglers are pre􏰁y much in full breeding plumage; with bright pale-yellow beaks and bold black and white plumage, they are strikingly hand- some. There have been many observa􏰀ons of individuals with wings in full feather moult as well, and it is likely that, during the spring period, White-billed Divers become completely flightless for a while, making it a cri􏰀cal period for this species.
We have some􏰀mes managed to see these White-billed Divers off Portsoy during Highland Flings, although our record has been of more misses than hits. They can be tricky to separate from their near rela􏰀ves Great Northern Diver. The key features are the larger size, the longer, upturned beak, paler head and steeper forehead of White-billed. The key difference is that the 􏰀p and final third of the beak is always pure or translucent white to pale yellow and there is never a dark line down the top of the beak in this area, which pale-billed Great Northerns will have.
So we have seen White-billed Diver move from a genuine rarity in the UK to a rather splendid but s􏰀ll uncommon visitor to our shores in the non-breeding season.
Andy Webb andy@andywebb.org.uk
White-billed Diver (Gavia-adamsii): Fred Derks 19