Sterne arctique (Sterna paradisaea, Arctic Tern)

syn. = Hirondelle de mer arctique, Sterne paradis, Sterna macrura

© Alain Fossé

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 juvénile/1er hiver, 19 octobre 2004, Saint-Mathurin-sur-Loire CoolPix seul

Sterne arctique Sterna paradisaea

 adulte, 1er novembre 2000, digue de Tarnos

ca 10-15 m, ISO80, F4, 1/241 à 261e s, non recadrées

ca 15-20 m, ISO100, F4, 1/276e s, non recadrée

 juvénile, 1er novembre 2000, digue de Tarnos

ca 10-20 m, ISO100, F4, 1/193e s, non recadrée

 1er hiver hirundo/Sterne arctique paradisaea ? (voir commentaires), 1er novembre 2000, digue de Tarnos

ca 15-20 m, ISO80, F4, 1/302e s, non recadrée ca 10-20 m, ISO100, F4, 1/193 à 573e s, non recadrées

Résumé d'une lettre de Klaus Malling Olsen, Danemark, 23·6·01 :

« It's an Arctic Tern:
evenly rounded head

all black, rather thin billseemingly very short legs1st-year: evenly fresh, pale-edged primaries, patterning of the mantle and covertsdark leading edge to the wing rather broad but within Arctic limits

mask fits both but only Arctic show black eyelids melting the eye with the mask »

Commentaires de Steve White, Royaume-Uni, 23·7·01 :

« Alain,

The bird is a juvenile/first-winter Common Tern.I've tried accessing your web page this morning to have another look but failed to connect. So, the remarks that follow are from memory - I sent the print out to Chris Kehoe for confirmation.Head pattern is wrong for juvenile or post-juvenile immature Arctic (I can't be more specific without a copy of the picture in front of me). It can't be an adult Arctic because it would not be in winter plumage and the tail streamers are far too short. Winter plumage Arctic would not show any orange/red at the base of the bill.So, it's a Common. And it's a juvenile because all the primaries appear to be of one generation; 8 primaries are exposed and there is no sign of moult (which any bird older than a juvenile should show at this time of year). There are some signs of brownish markings on (I believe} the tertials but these are worn off all the coverts, which are heavily abraded.

I hope this helps, Regards, Steve White. »

Commentaires de Klaus Malling Olsen, Danemark, 17·8·01 :

« Dear Alain

I have now had a new look at the tern, which still to me looks like an Arctic. I must stress, that to be 100% sure I would have liked to see how short the legs really were, but the had and bill shape, the lack of clear white eye-lids and the very weak juvenile pattern of mantle and scapulars looks right for an Atctic. Also, many Common shows broader pale edges to wing-coverts, highligtening the effect of a paler midwing area, which i cannot see on the actual bird.

If the birs was seen in flight, ID would have been much easier. Have anyone any impressione here? »

Commentaires de Steve White et Chris Kehoe, Royaume-Uni, 22·8·01 :

« Alain,

Thanks for you e-mail and the summary of Klaus Malling Olsen's comments. Chris Kehoe and I have looked again at the photographs and are more than ever convinced that the bird is a Common. 1. Head pattern: appears absolutely typical of Common with dark loral spot in front of eye isolated from both the crown and the ear-covert lobe. On Arctic a dark area below the ye joins the lores and dark ear-coverts. The dark crown has a very diffuse border with the white forehead with a large area of the forecrown showing a flecky or peppered pattern. Although this feature is shown to some extent by Arctics, our experience is that this border is usually more distinct. 2. Bill pattern: Juvenile Arctic usually has an all-black bill with any pale soon lost. For a bird to show such obvious pale (reddish) colouration on both mandibles (as the picture clearly shows) would be unusual in Arctic but expected in Common in transition to first-winter plumage in late autumn. 3. Carpal bar: even when worn we have never seen an Arctic with a carpal bar this black or nearly so extensive. Again, this feature is typical for Common. 4. Primary pattern: the underside of p10 (outermost primary) shows an extensive dark tip. Arctic shows less black with much grey or white extending almost to the tip and bordered there by a black fringe. Although some Commons may very roughly approximate this Arctic pattern (one was illustrated in our published article)we've never seen an Arctic approximating the Common pattern. We believe this is perhaps the strongest indication that the bird is a Common. 5.Innermost primaries on upperwing: these show narrow white edges on the inner webs - typical of Common. Arctic would normally show wider white edges. In one photograph the tertials are displaced to reveal p3, whose very weal white edges is even more indicative of Common.

6. Structure: it just looks like a young Common Tern! In particular, the head does not look neatly domed (rounded), the bill looks too long and downcurved, and leg length cannot be seen (only the foot is visible), being obscured by the drooping wing. »

Loire, Saint-Mathurin-sur-Loire, Maine-et-Loire (49), France, 47° 24' 47" N, 000° 20' 42" W

Tarnos, Landes (40), France, 43° 31' 51" N, 01° 31' 23" W 

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