PHOTO GALLERY
NOTE: The following responses were received after a small photo was posted at the bottom of the 'mystery gulls' webpage.
RESPONDENT 1
Lastly, I should note that I probably would not have called the first-winter bird at the bottom of the series a Lesser Black-backed Gull. The shade of the upperparts looks both too pale (not contrasting with the head and underparts), and the pattern does not seem scaly enough.
RESPONDENT 2: Alvaro Jaramillo <[email protected]>
Perhaps the more interesting observation I have is of the first winter bird photographed in March. If this photo is from March it can't be a Lesser Black-backed Gull. At that time the feathering would have had about 8-9 months of wearing and bleaching and would not look this fresh and uniform. The bird pictured is a juvenile based on how fresh and crisp this bird it. Given that its a juvenile in March, it has to be a southern hemisphere breeder and therefore a Kelp Gull. In March its typical to see this plumage stage in Chile/Argentina for example. Please pass on these opinions to whoever you want. I will keep thinking about the right "second year" bird some more.
NOTE: The following responses were received after a set of larger photos of both sides of the bird, including zoomed-in images of head, wings and tertials, were posted.
RESPONDENT 3
Concerning the age of this bird (and the visible wingcoverts, tertials and scapulars) :
I consider the wingcoverts and scapulars of the gull depicted at the mentioned link to be in its second calendar year and is showing a largely second generation scapular, tertial and upperwingcovert area. The tertials for instance show a blackish brown base with a subterminal bar on a whitish base. This pattern is rather typical for a second generation feather. The same applies to the upperwingcoverts and scapulars: these are not dark-centred with only creme tips and edges (as in juvenile plumage), but contain pale internal markings creating either a barred effect or anchor patterns. Moreover, the beyond the tertial protruding (juvenile) primaries are worn and bleached, suggesting that they are rather old and are most probably attained during the preceding calendar year.
RESPONDENT 4: Bruce Mactavish <[email protected]>
A 1st winter Lesser Black-backed Gull-like gull with juvenile scapulars in March could be a Lesser Black-backed Gull. There is a 1st year Lesser Black-backed Gull in St. John's, Newfoundland that arrived October 2001 and is still present at the time of this writing. It retained 100% juvenile scapulars well into March and probably through March. On April 3O 80% of the scaps were still juvenile. The bird was easily followed through the winter because it lived at city pond stealing bread thrown out to tame ducks. Perhaps the diet was nutrient deficient enough to prevent moulting of scapulars. However, 1st winter Lesser Black-backed Gulls, even the ones with a rich diet of human garbage, retain many juvenile scapular into mid and late winter - much like smithsonianus.
Juvenile scapulars of Lesser Black-backed Gulls are normally fairly uniform dark with a narrow, sharply defined pale fringe. The bird in question shows pale internal markings on the scapulars. This contrast could show up on 1st winter LBBG scapulars if the paler internal markings encompassed by the darker anchor shape mark were bleached by sunlight.
The head shape, the bill shape and colour, the lower neck streaking, the primary projection - the over all jizz, is dead on for Lesser Black-backed Gull.
RESPONDENT 5: Dick Newell <[email protected]>
I think the problem here is to decide between graellsii and atlantis. I don't think the bird is a juvenile - many of its scapulars have obvious 2nd generation double anchors. The pattern of these feathers is very unusual for graellsii - they rarely have that much pale cream. Juvenile atlantis is (to my eye) practically indistinguishable from graellsi, and I guess the problem doesn't get much easier with 1st winters.
Structurally, I really don't see this bird as a Kelp Gull. It's shape is very like a graellsii and probably atlantis too.
RESPONDENT 3
As I have already made clear to Floyd , I am sure that this bird shows obviously fresh second generation scapulars, upperwingcoverts and tertials (note pattern of all these feathertracts). Moreover, a combination of worn and bleached primaries and fresh juvenile scapulars and wingcoverts would be very strange.
Atlantis attains second generation scapulars and also wingcoverts during the post-juvenile moult from August of their first cy. At least the feathers acquired during late summer and autumn of their 1cy should be should be worn by March (2cy).
The gull concerned seems to have acquired all second generation coverts, tertials and scapulars recently (given their freshness) and these feathertracts seems to be renewed in one wave (no significant differences in wear between single feathers and/or feathertracts). This timing and sequence of the moult fits a LBBG well.
RESPONDENT 6
I took a peek at the bird. Although some feathers do look fresh, the primaries for instance do appear to be rather worn and bleached (they should be blackish on a fresh juvenile). Also, although the fresh feathers look juvenile type, they most probably are not. In some of the enlargements you can see some greater coverts next to the tertials to be rather worn. The inner middle coverts have been replaced and all scapulars are second generation. Superficially they are reminescent of juvenile feathers, but their patterning and slightly warn tone exclude this possibility. Overall it looks like a rather normal graellsii-type Lesser Black-backed Gull. But, as I'm not familiar with American Gulls, I cannot rule out those possibilities.
RESPONDENT 7: Martin Reid <[email protected]>
I want to endorse the comments of Bruce, Dick, and Peter , in that in almost all respects this bird looks good for an LBBG-type (bill proportions, head shape and streaking, very short tail/long primaries). I feel that structurally it is far from a typical Kelp Gull (esp. bill shape, tail length, and while closer to Atlantis YLGU, the very short tail and rather slender bill is a perfect match for LBBG-types and rather atypical of all the YLGU forms.
Note that the primaries are extremely faded and worn (they are usually very black, and apparently resistant to such wear/fading in LBBGs) - I feel that this rules out any notion that the bird is a recently-fledged juvenile. The only thing at all odd for 1B LBBG on this bird is its apparent stage of molt: many (but not quite all) of the scaps/mantle feathers seem to be 2nd-gen., and while their pattern is on the pale side for LBBG, I don't think it is out of range; we are not used to seeing 2nd-gen wing-covert feathers on 1B LBBGs, as we expect this tract to be molted in the "summertime" along with other tracts that create the first-summer" appearance. Thanks to the pioneering work of the Muusses, we now know that a few juv LBBGs seems to replace some wing coverts even while still being attended by their parents; a quick look at these mega-early replacement 2nd-gen coverts shows a pattern fairly similar to that of the Caribbean mystery bird. Clearly the mystery bird's coverts feathers look too fresh to have been replaced at the nesting grounds - but assuming there is a physiological reason for this individual to have replaced them in, say Feb, then their pattern looks pretty good for LBBG.
Lastly, let's not forget that there is a LBBG-type that regularly replaces many of its 1st-gen wing-coverts in Feb/March: heuglini. I'm not saying that the mystery bird is a heuglini - I'm just pointing out that a strategy of Feb-March covert replacement is evident in a LBBG-type that winters in different environment than most graellsii, so it is not much of a stretch to conclude that as graellsii/intermedius invades a similar wintering environment to that of heuglini (Caribbean/NE South America), it will also adopt this molt strategy.
RESPONDENT 8: Nick Rossiter <[email protected]>
I would be slightly worried if I were the recorder for Trinidad, building up a collection of LBBG, a number of which are far from classical. In the first-year bird under debate, the problems of early moult are resolved if the gull is considered to be atlantis. The bill might be rather thin for a southern atlantis but northern atlantis can show such bills. Northern atlantis moult a bit later than southern ones but are still ahead of LBBG.
I thought a second-winter in December shown earlier on the Trinidad site (recorded 2 December 2001) which was identified as an LBBG, looked much more like southern atlantis with its chunky bill with steep culmen angle and prominent gonydal angle. The chest is also bold and, with the usual caveats about mantle colour in photographs, the mantle shade and colour (blue-grey) also appear right for atlantis. The pale head with a pronounced eye patch is also spot-on.
The likelihood of atlantis occurring in Trinidad at some time must be fairly high because the NE trade winds flow straight from the Canaries to the West Indies.
Interestingly some recent DNA studies have differentiated southern atlantis from northern atlantis, atlantis (particularly the southern form) from michahellis and indicated that atlantis pre-dates michahellis (Liebers, Helbig and de Knijff, Molecular Ecology 10 2447-2462, 2001).
RESPONDENT 2: Alvaro Jaramillo <[email protected]>
I have been away doing tours and have not gotten back to this issue of the gull which I stated was a juvenile in March. I have read the comments by others and looked at the larger photos posted by Floyd and of course you are all correct. This is NOT a juvenile bird, the primaries are indeed worn. So my previous comments that this must be a Kelp based on plumage age is incorrect. Thanks a lot for taking a close look and making me look twice. That's the beauty of refutable hypotheses - the only way we can move forward with some of these problem gulls.
