Commentary on Philippe Dubois' Paper on Atlantic Yellow-legged Gulls


Dubois, P J, (2001), Atlantic Islands Yellow-legged Gulls, an Identification Gallery, Birding World 14(7) 293-304.

Yésou, P, (2002), Trends in Systematics, Systematics of Larus argentatus-cachinnans-fuscus Complex Revisited, Dutch Birding 24(5) 271-298.

Field work:

Canary Islands: September 1991 (author)

Azores: mid-August 2000 (author)

Canary Islands: late July 1997 (Jiguet)

Specimens: from Azores, Atlantic Morocco and Madeira.


While in both papers above the term atlantis is erroneously reserved for those from the Azores (see below), here the term is used as by Dwight (1925) extending to the Azores, Canaries, Madeira and Atlantic Morocco with extension to Atlantic Iberia by the studies of Rossiter (2002). The term michahellis is used here for the Mediterranean Yellow-legged Gull.

Claims by Dubois

Comments NR

p.293 General


Scanty treatment in the literature of Atlantic Yellow-legged Gull Larus michahellis atlantis

For birds of known origin atlantis is as well covered as michahellis in the printed and electronic literature. See for instance Dwight's Original Texts on atlantis, Home Page Yellow-legged Gulls and Norman van Swelm's ID paper . For wingtip patterns of michahellis in their breeding areas we are reliant on Isenmann (1973).

Dwight first described the form atlantis from the Azores and that the Azores form is the true atlantis.

Not true -- see Dwight's Original Texts on atlantis with commentary

Third-years from the Azores show dense streaking on the head, look completely grey-hooded at a distance -- a feature unique to Western Palearctic Gulls.

This is certainly a striking feature. However, some third-winters in the western Canaries can also show quite marked hoods.

Juveniles and first-winters from the Azores are quite variable but are still often identifiable.

Very doubtful - juveniles from Madeira and the western/central Canaries can be as dark

p.294 Structure and Jizz


atlantis are generally more compact, shorter-legged and shorter-winged than michahellis. Many atlantis also have a somewhat heavier and less 'hatchet-tipped' bill than michahellis. Sexual and individual variation, however, mean that structure is of little use for identifying a lone bird.

The biometric differences between atlantis and michahellis are well established -- see Available Statistics: Tables 1-2 and Norman van Swelm's ID paper . Some of the differences are very significant such as leg difference and could be used to support strongly the identification of a lone bird.



Juveniles from the Azores in mid-August are very dark (some recalling juvenile smithsonianus)

Agreed. Juvenile atlantis could be confused with smithsonianus

Dark chocolate upper mantle, those from Canaries often paler and more chequered

In July 95% of juvenile atlantis in Tenerife are a dark grey-brown and only 30% are chequered Statistics for First-years: Tables 6-8 . Therefore this claim is not accepted. Also not all the Azores examples shown appear to be uniform in texture.

Head colour is variable but usually like in Madeira birds show a darker head than birds from the Canaries where streaking is mainly around the eyes.

95% of Tenerife birds in late July show a very dusky head. See also plate 12 of Dubois' paper for a counter-example. Not accepted.

Fairly uniform scapulars

As in 70% of Tenerife birds in late July

Tertials are similar to michahellis with many having fine pale fringes or pale indentations or notches.

This is very interesting. Of five shown in Dubois' paper, three look to me like graellsii (narrow fringes) and two show notched fringes. 88% of southern atlantis show graellsii-type pattern Statistics for First-years: Tables 6-8 so if confirmed on a larger sample, Dubois' finding is significant. However, genetically it would suggest that Azorean atlantis is close to michahellis as suggested by Liebers et al (2001). Some northern atlantis also show more white on the tertials (Stats ibid).

In flight obvious dark secondary bar and dark greater coverts bar, many lack a pale window on inner primaries. Canary birds do usually show a faint pale window.

50-60% of juveniles in Tenerife show two bars on the inner-wing in July and August. 75-80% of juveniles in Tenerife in July and August have an indistinct pale primary window (often difficult to see) and 15-20% no window. Possibly some difference at the population level but we need statistics from the Azores.

Dark underwing coverts with slight contrast from the primaries.

Rather similar in the Canaries with 45% of juveniles in July and August showing some contrast and 20% no contrast

Broad dark tail band unlike typical michahellis

As in Canaries

Dark markings on front of tarsi and on the feet. Madeira birds are similar. In michahellis such markings are shown less commonly

An interesting observation but, if shown by Madeiran atlantis, is obviously not specific to the Azores. Slides at IGM6 showed this feature on juveniles from Fuerteventura in the first half of November (Andreas Buchheim).

p.298 First-summer


It is not always easy to distinguish between juveniles and first-summers in mid-August. The Canarian birds become much paler on head and underparts.

The difficulty of distinguishing juveniles and first-summers also applies in the western and central Canaries where primary moult is one of the criteria used. Birds in Fuerteventura have a greater tendency to become paler.

Uniform underwing

As in the Canaries

p.299 Immatures


Plates 21 and 22

Not accepted as typical Canary birds. A few % of first-years in flocks are large and strong with long legs and pale heads and bodies. But these untypical birds are either extreme atlantis or visiting michahellis. Some much darker birds could have been shown here with the typical structure of atlantis.

p.300 Second-summers/third-winters; plates 22-29


Head streaking

 See above

Moult in atlantis starts earlier than in michahellis and is perhaps more prolonged

Not sure that this can be inferred from studies only undertaken in late summer and autumn. However, Canary birds do seem to be slightly ahead of michahellis but the difference is small.

Iris is very pale whitish-yellow in Azores and Canaries while in michahellis it is a relatively dark yellow

Agreed that it is a very pale yellow in atlantis but michahellis from SW France and eastern Andalucia also seem to have very pale iris as do a number of adults and older immatures shown in various web pages. The bird in plate 29, alleged to be michahellis, is rather strange. Its head is quite streaked and its legs are rather short. Its origin is surely unknown.

p.302 Adults and near-adults


Iris colour

See above

Two types noted in late summer: white heads and obviously streaked heads, the latter possibly fourth-winters.

An important observation. Possibly the adults are closer to other atlantis than generally realised.

p.304 Discussion


Plate 30 (skin comparisons) indicates a clinal change in mantle colour from michahellis (palest) to Essaouira, Atlantic Morocco to Madeira to Azores (darkest)

The effect may be exaggerated as the Azores bird is in fresh September plumage and the michahellis and Morocco bird are in more worn April plumage (no month for Madeira bird). However, all three atlantis are significantly darker than the michahellis as expected.

No mtDNA difference between michahellis and atlantis by Helbig.

Differences now found -- see Liebers et al (2001) Review of recent genetic analyses and comparison with morphological work

Azores atlantis is distinct from michahellis


The Canarian form is close to the Moroccan one

Agreed -- they are both atlantis

The Canarian form is closer to michahellis than to Azorean atlantis

Not if you consider size, structure, wing-tip pattern in adults, mantle shade and juvenile plumage characteristics.




1) atlantis ... has been described from the Azores (Dwight, 1922). Some authors ... extended this name to the birds breeding in the Canary ... and Madeiran Islands ...

In reality Dwight (1925) defined atlantis as occupying the coasts and islands of north west Africa and used specimens from the Canaries in his 1922 paper.

2) More recently Dubois (2001) concluded from field and museum studies that Azorean birds differ from those breeding in the Canary and Madeira Islands in a number of aspects.

There may be some minor differences but there is as yet no phenotypic evidence for any separate taxonomic treatment.

3) It is wise to restrict the use of the name atlantis to the birds breeding on the Azores as Dwight initially did ...

We should certainly consider atlantis to occupy the range given by Dwight in his 1925 paper. Modifications using results from recent studies lead us to also include most of Atlantic Iberia within the atlantis range.

© Copyright Nick Rossiter 2002

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