Fantasy of Light- an interesting loon

Local CT birder Keith Mueller kindly allowed me to post a few images of a loon seen recently off a Rhode Island pelagic, November 2011. I noticed the bird on his blog and it’s appearance  immediately caught my eye. In the photos, it’s obviously a large loon with a thick neck, heavy, pale bill, (which appears slightly upturned), predominantly ‘frosty’ above with pale feather markings and a very pale head – lacking the clear divide of black and white seen on Common Loons.  It seems to be a juvenile Yellow-billed Loon! Or is it? (CLICK FOR LARGER IMAGES)

Yellow-billed Loon is a high Arctic species, an extreme vagrant  rarely recorded in the east. The two most recent records, both adults, were seen in PA in May 2007, http://home.earthlink.net/~pomarine/id73.html  and in Maine in October 2010 http://www.mainebirdingtrail.com/Odyssey10.htm  It is definitely a species that should be looked for in New England waters.

While it does look unusual, dissecting the bird, thanks to digital technology, reveals some clues, that together, identify it to species. YBLO is a large, thick-set loon with a powerful, upturned bill, large feet and a thick neck. In juvenile plumage the upperpart feathers are quite pale-fringed and give a frosty appearance to the upperparts, moreso than on Common Loon, whereby the fringes are duller and not as contrasting. The bill is ivory-yellow, though at a distance exact colors may not be evident. The sides of the head on the RI bird are very pale, isolating a dark eye in a plain face, quite unlike Common Loon which is typically blackish and well delineated from the white neck. All these features are somewhat close to the above bird, but we need to look closer and take into account the vagaries of light on dark and light tones when assessing loon plumages.

The bird is in fact a Common Loon and an educational individual. The one main feature I left out is that YBLO show pale primary shafts at all ages, a feature hard to see in flight but lacking in Keith’s photos and point to Common Loon (which has brownish primary shafts). But still, the other features superficially recalling YBLO need some explanation. I had initially thought the bird to be a juvenile due to the pale feather fringing and asked an acquaintance of mine, expert Irish birder Killian Mullarney to comment on the identity. He kindly replied as follows, confirming the bird as a Common Loon rather than the rarer alternative:

“The  liberally white-spotted wing coverts establish that it is an adult, not a juv. The uniformly light greyish colour of the bill is strongly indicative of Common Loon. Even in opportunistic shots such as these, I’d expect to see some hint of a more ivory-coloured or pale yellowish tip to the bill, as well perhaps as a bluish-grey shade toward the bill base, especially the lower mandible and the nasal groove of the upper mandible. The dark culmen of Common Loon is often very difficult to make out in photos like this, it can so easily be ‘lost’ against the background colour. The extent and shade of winter head pattern does look unusual for a Common Loon, reminding me of how they often look when they are in transition from basic to alternate plumage in spring, when the head and neck can appear much lighter and mealier in texture than a typical winter adult.

The bill pattern is hard to make out, especially the extent of dark on the culmen, but any dark on the cutting edges of the bill aren’t obvious, but still, as Killian notes, some darkening at the base of the bill and a more ivory-tinge to the bill perhaps should be evident.

 

Deceased adult Common Loon, Plymouth, Mass. Feb. Note white upperpart spotting, extent and darkness of black on head and neck and darker culmen and cutting edges to bill. Not much compensation for dipping an adult Ivory Gull!

I saw my first Yellow-billed Loon (also known as White-billed Diver) in the UK in 1987 when I was 18 and include a scan of my journal which notes in detail, the features typical of Yellow-billed Loon noted above. Enjoy!

 

Yellow-billed Loon, Filey Brigg, UK (from field journal, J.R. Hough)

 

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