Hi Tweets,

Here's an interesting item from ID-Frontiers about California Gulls Larus
californicus on the separation of its subspecies, nominate L.c. californicus
and L.c. albertaensis. Given that, regionally, we're up to the labonza in
CAGU's of various ages 'n stages for much if not all of the year, depending
on location, Cascadian birders are in a position to make a contribution
here. I'd just ask that if you do make worthwhile observations, and reply
directly to Jon King &/or Frontiers, that you 'CC' them to Tweeters as well,
as this is one of our 'wallpaper' birds, often a backdrop against which we
search for the more unusual species. Thanks.

Michael Price A brave world, Sir,
Vancouver BC Canada full of religion, knavery, and change;
mprice at mindlink.net we shall shortly see better days.
Aphra Behn (1640-1689)

The original remarks were from Alvaro Jaramillo during his recent work in
Alberta:

AJ:

>1) _albertaensis_ California Gull. Some of you know that there is a
>subspecies described for the northern breeding California Gulls, these are
>supposed to be larger and paler than the southern populations. Presumably
>both winter in California but only the nominate summers and breeds in
>California. I assume that the one I know best is the nominate form. In any
>case, if anything stands out on the Alberta subpecies is that they average
>larger. Some of the Alberta birds are noticeably larger than the typical
>California Gulls I see here, particularly when compared to Ring-billed
>Gulls. The difference between the two species appears to be greater in
>Alberta than in summer here in California. However, they still are
>substantially darker on the upperparts than Ring-billed Gulls. It is my
>personal opinion that the darkness of the mantle is not substantially
>different between nominate and Alberta California Gulls. I have yet to read
>the paper that describes the subspecies, so I don't know how different they
>are supposed to be, but it is my guess that one cannot have any real
>confidence in field identification of this subspecies away from the
>breeding areas.

And Jon King replied:

>I am grateful to Alvaro for raising the spectre of albertaensis California
>Gull; I have been tempted to discuss this before on IDF, but now he can take
>the blame for opening this can of worms! My experience is that there is
>little or no awareness among birders that there are two recognised
>subspecies of California Gull (probably because the key reference appeared
>after the second edition of Grant's 'Gulls'). The reference is: Jehl, J. R.
>1987. Geographic variation and evolution in the California Gull (Larus
>californicus). The Auk 104: 421-428.
>
>As some of you will know, Steve Howell and I have been working intensively
>on gulls (primarily here in CA) for a couple of years, and albertaensis has
>been one topic of particular interest. The race albertaensis is poorly
>known, especially from an ID standpoint. On current knowledge, subspecific
>identification in the field is normally possible only when both California
>Gull taxa are side-by-side in excellent lighting. Albertaensis does indeed
>average larger and paler than californicus, and although the former tends to
>show the characteristic California Gull 'facial' features of dark eye,
>relatively long bill (with red/black spots in adults) and slim head, in many
>ways albertaensis can often appear intermediate in size and structure
>between californicus and smithsonianus Herring Gull. Indeed, separating
>albertaensis from Herring Gull can at times be as problematic as its
>separation from californicus.
>
>At Bolinas Lagoon (near Point Reyes, CA), I have found (with Steve and
>others) that albertaensis is at least a scarce spring migrant in north
>coastal CA. In March and April, we have occasionally found them amongst
>californicus. Although we have identified only 'grey mantled' birds (i.e.
>3rd calendar year plus) birds to our satisfaction, we have suspected some
>large, pale 2nd cal year birds to be albertaensis also.
>
>Although the difference in the shade of grey is slight, it is discernable.
>On average, the difference perhaps represents 'half a shade' of grey, and is
>greyer, less blue toned, than californicus. The following are, however,
>critical to determining shades of grey: (a) very thorough study of
>californicus, in order to be familiar with the extent of upperpart color
>variation in that taxon, and (b) cloud cover. On more than one occasion, we
>have watched a large flock of California Gulls in the sun unable to detect
>any albertaensis, then some cloud rolls in and suddenly a couple of
>albertaensis 'jump out' at us.
>
>Size is helpful also, but again familiarity with californicus is essential.
>There is probably as much (or more) intra-taxon variation in size as there
>is inter-taxon variation, due to sexual dimorphism and individual variation.
>In addition to being larger (circa 5-10% in linear measures), albertaensis
>averages bulkier (more Herring like), with a deeper bill and heavier chest
>than californicus (according to Jehl, albertaensis averages 27% heavier than
>californicus). As would be expected of a longer distance migrant,
>albertaensis appears to show a slightly longer primary projection than
>californicus (pers. obs.). I have seen some slight (though apparently
>inconsistent) differences in primary pattern between the two taxa,
>albertaensis averaging more white on outer primaries (but this is VERY
>provisional, and I am still working on the details).
>
>In addition to the apparent status of albertaensis at Bolinas, Steve Howell
>believes this taxon to be the principal California Gull taxon in winter in
>Baja. I saw a second cal year albertaensis in Louisiana in April 98, and
>Steve Cardiff and Donna Dittmann have amassed an invaluable collection of
>that taxon from the state in the LSU Museum of Natural Science (which also,
>intriguingly, includes at least one apparent californicus from Cameron
>Parish, Louisiana). Logic appears to suggest that albertaensis should winter
>to the south and east of californicus, and these (very limited) observations
>support this.
>
>The same logic implies that albertaensis is the taxon to be expected as a
>vagrant in the east. I suspect that most observers 'mental image' of
>California Gull is based upon the commonly occurring and easily seen west
>coast californicus, and that the greater similarity of albertaensis to
>smithsonianus may therefore be an underestimated problem. Given the current
>splitting trend, especially in large gulls (cf. the
>Herring/Yellow-legged/Lesser Black-backed group), there should be
>considerable interest in clarifying the characters of albertaensis.
>
>For an article in preparation on California Gull variation, I would be very
>interested in opinions on this (apparently overlooked) issue.
>
>Jon.
>
>==================================
>Jon R. King
>Point Reyes Bird Observatory
>4990 Shoreline Highway
>Stinson Beach
>CA 94970, U.S.A.
>
>E-mail: king at prbo.org
>Voice-mail: (415) 868-1221 x.42
>Fax: (415) 868-1946
>Tel. (June-August): (530) 595-3460
>Fax. (June-August): (530) 595-4423
>==================================
>