tirsdag 8. desember 2009

Smithsonianus lookalikes

Dark argentatus Øra, Fredrikstad, Dec 2006 - phoro: SEN

If you study gulls regularly, you will eventually come across individuals that show characteristics that challenges your own mentally accepted range of a species' variation. We will here present pictures of a number of such individuals showing a strong resemblance to american herring gull Larus smithsonianus. Some of these individuals were initially thought to be true yanks by the observer (and expert opinion seemed to support the ID), but as you will see later on, extreme caution should be excercised before claiming smithsonianus in Europe. The individuals presented will be ordered, starting with relatively easy individuals, ending with extreme birds..All the individuals were photographed in the southern parts of Norway, most of them near Mandal - the southernmost city in Norway.

We have chosen to publish this entry in english, since this subject is likely to be of more than just local interest. With gulls, one could probably write a book about every picture, and some readers may react to the brevity of the picture comments. So be it...Our intention is merely to present difficult individuals and maybe get some reaction from gull experts out there.

The paper to read on the identification of american herring gull: Lonergan, Pat and Mullarney, Killian (2004): Identification of American Herring Gull in a western European context Dutch Birding 26(1): 1-35

Click the photos for larger versions.

Individual #1

1w (2cy) "argsmith" Gismerøya, Mandal 21.03.2004 - photos: IFL

A relatively common type of dark argentatus. It is quite a bit darker than the average bird and has an almost all-dark tail, but otherwise the feather patterns fit argentatus.

Individual #2

1w (1cy) "argsmith" Lillehavn, Mandal 12.10.1998 - photos: IFL

This bird shows darker and more velvety brown breast, belly and lower neck than the average argentatus. It also has a rather strongly barred rump. The relatively large amount of white on the sides of the tail and too much white on the undertailcoverts (among other things) do, however, indicate that this individual is just a dark argentatus.

Individual #3
1w (1cy) "argsmith" Gismerøya, Mandal 28.10.2005 - photos: IFL

A bird with heavy barring on both rump and undertail-coverts. It also has an almost all-dark tail. Rather reminiscent of some pale smithsonianus, but argentatus cannot be excluded of course...

Individual #4
1w "argsmith" Sjøsanden, Mandal 16.10.2001 - photos: IFL

This bird is even more similar to smithsonianus than #3 with even heavier barring on the undertail coverts/rump and a darker appearance overall. It doesn't show the typical velvety brown underparts, however, but appears streaked, especially on the breast and neck. Notice also that the white margin of the outer tail feather reaches the tip of the feather. Most likely argentatus...

Individual #5

1w (2cy) "argsmith" mar 05, Øra, Fredrikstad - photos: SEN

Very plain brown (without streaking) especially on the lower breast/belly and lower hind-neck and whitish head, inviting confusion with smithsonianus, but too weakly barred undertail-coverts, "wrong" greater-coverts and lacks pale base to bill.

Individual #6

2w (2cy) "argsmith" Mandal havn 15.12.2002 - photos: IFL

A very heavy-set bird with nice, dark tail and contrasting chocolate brown axillaries and underwing-coverts. The rump was rather heavily barred for a 2nd winter bird (barely visible on the photos).

Individual #7

1w (2cy) "argsmith" Øra, Fredrikstad 10.01.2005 - photos: SEN

Very bad photos of a very striking gull with plain brown from the breast and all the way down to the vent. It also had an all dark tail, heavily barred rump and rather heavy/broad barring on the undertail coverts as well . The head is contrastingly pale and the bird also shows a greater covert bar and tertials compatible with smithsonianus. Too bad we didn't get any flight shots..

Individual #8
2s (3cy) "argsmith" Gismerøya, Mandal 11.06.2006 - photos: IFL

A 2nd summer bird with heavily barred undertail-coverts and broad tail-band. We cannot recall having seen anything similar on any published photo of argentatus/argenteus. Comments are very welcome!

Individual #9

3w/3s "argsmith" Gismerøya, Mandal mar/apr 2004 - photos IFL

Same bird may 2004 - photos IFl

Same bird jul/aug 2004 - photos: IFL

An individual with smithsonianus tail and the dark patterned secondaries with black restricted to the basal parts of the inner webs also fit well. Comments are very welcome here too..

Individual #10
1w "argsmith" Gismerøya, Mandal 29.12 and 08.11.2003 respectively - photos: IFL
Rather similar to #5 in plumage.

Same bird feb/mar 2004 - Looks rather nondescript in worn spring plumage...
Same bird nov 04 (2cy) - oh boy...
Same bird early spring 2005 (3cy)

A very good smithsonianus candidate. We sure would like to get some comments on this one..

Individual #11
2w (2cy) "argsmith" Gismerøya, Mandal late des 2005 - photos:IFl
Same bird jan/feb 2006 (3cy) - photos: IFL

Very similar to #10, and difficult to label argentatus with that tail/rump. But is argentatus excluded? Please comment!

Individual #12

A rather smithsonianus-like individual with heavily barred rump and undertail-coverts, dark tail, rather plain dark breast/belly etc. The main problem is that it is wearing a ring. This bird - Black J1118 - was ringed as a chick in a colony of (argentatus) herring gulls at Storøytåa, Mandal, Norway 25.06.2009.

Individual #13
Ahh! At last a true smithsonianus! But what is that blue thing on the birds' tarsus?
juv "argsmith" Gismerøya, Mandal 09.08.2006 - photos: IFL

This bird - Blue J6XN - shows almost all smithsonianus features to perfection: The dark tail, the heavily barred rump and undertail-coverts, dark based greater-coverts and tertials, restricted primary window and chocolate brown appearance of entire plumage. The only thing that separates this bird from a perfect smithsonianus is that it appears a bit too streaked on the breast/belly, a feature that would probably go unnoticed in less favourable light...
The ring also poses a problem, of course. This bird was ringed as a chick on Storøytåa, Mandal, (southernmost) Norway 23.06.2006 in a colony of argentatus herring gulls. The prescence of birds looking like this, evidently born in a norwegian population of (argentatus) herring gulls, makes positive identification of smithsonianus in Europe very difficult...For all we know, even previously accepted records may have to be reviewed...

It is of course a possibility that a smithsonianus has interbred with argentatus for years in the Storøytåa colony. This could explain the regular occurence of smithsonianus-lookalikes in the area, but it wouldn't make it easier to get smithsonianus records accepted...

Please don't hesitate to comment on this entry!

Inge og Stein, December 2009.