Before I launch into the DBQ answers, it’s time to revisit an old quiz. Edward wrote in to say that our conclusion on a bird we featured a while back in this DBQ may have been erroneous. He writes that the bird more closely resembles a Brown Booby than the juvenile cormorant we deemed it to be. Edward is right in pointing out that that species is hardly unheard of off the South Carolina coast, so I wanted to bring the debate to your attention and see what you think upon considering this idea.
Now to the current quiz. There was no debate on this one; Bird A was universally recognized as a Northern Fulmar (NOFU), and Bird B as a Mute Swan. Indeed, this one was not intended to be very tricky, but more to pull out a couple species we see dead only rarely on SEANET beaches. The reasons for that most likely do not reflect the overall commonness of each species. The Mute Swan, in particular, is a non-native species that has risen to nuisance status in many regions on the United States, and we have several volunteers who report dozens of live swans every time they survey their beaches. Yet, we don’t get them reported dead very often. In fact, the last time we had a Mute Swan reported was back in 2011 in Rhode Island. Whenever a bird is uncommon in our database, we wonder why. Is the species rare overall? Is it found so far offshore that a carcass is unlikely to wash up on a beach? Do the birds go elsewhere when sick or dying (like a sheltered bay or estuary, rather than the open water near a SEANET beach)? I don’t know the answer in the case of Mute Swans. But at least making the i.d. is simple–a very large (see index card in photo for reference), all white bird with an exceedingly long neck. I suppose egrets partly meet that list of characteristics, but they are far less massive and they have long legs with unwebbed feet: far different from our Bird B. In Bird B, we have the additional benefit of an intact skull. Edward pointed out that the skull shows the knobby projection at the base of the bill that marks the Mute Swan. Compare the bill profiles of Mute Swans with two native North American swan species:
Bird A, the Northern Fulmar, is another species that has not turned up on a SEANET beach since 2011 when Frank Kenny found on in New Jersey. Here is a side-by-side of that bird and Sarah Porter’s find:
In both cases, after the initial glance that often makes one think of a gull, closer inspection reveals the thick, stocky bill that makes both these birds unmistakably Northern Fulmars. What is interesting is the substantial difference in plumage coloration. Frank’s NOFU is almost white overall, while Sarah’s is a mix of grays and some interspersed brown feathers over the mantle and upper wing. What’s going on there? The answer is twofold.
First off, what’s with the light bird and the dark bird? Are they different subspecies? Different sexes? It’s a bit complicated, so let’s start with the basics.
Northern Fulmars are aptly named on both counts. “Fulmar” derives from “foul gull” (and I know many will argue that gulls are foul enough) due to their charming habit of projectile regurgitating stomach oils as a defense. The “northern” refers to their range. The species is circumpolar and nests from the high Arctic down as far south as Newfoundland and France in the Atlantic and the Aleutians in the Pacific. They winter from the limit of the pack ice down to the mid-Atlantic states and sometimes occur as far as Florida or even (very rarely) Mexico. Given this, it is not unusual to have NOFU anywhere along the SEANET territory during the non-breeding season, approximately September through April. After that, they mostly head north to breed, though in some years substantial numbers persist as far south as North Carolina as late as May or June.
The species is divided into two subspecies: Pacific (Fulmarus glacialis rodgersii) and Atlantic (P.g. glacialis). Our Atlantic subspecies is larger overall, though within the subspecies, the high Arctic breeders are smaller than birds breeding in boreal regions (farther south). Also within the Atlantic subspecies, there are what we call two “morphs” or color varieties: light and dark. That gets us to the main difference between Sarah’s NOFU and Frank’s. In the Atlantic, the light morph is more common, except for a few pockets in the high Arctic where the dark morph prevails. Even though Sarah and Frank’s birds look rather different in their coloration, both of these would be classified as light morphs since both have all white bellies, breasts and heads. This gives the birds a coloration pattern similar to a Herring Gull overall.
Dark morphs are harder to find in the Atlantic, so most pictures of them come from the Pacific where they are more common, but do check out these photos at neseabirds.com to see some very nice comparisons between the two.
Finally, that gray/brown mottling on Sarah’s bird. That is evidence of molting going on in this bird, where new feathers are coming in amongst the old. Edward points out that that makes this a bird older than 1 year since it is now replacing those older, worn feathers.