graellsii

LBBG 12cyAH6, May 03 2003, Voorhaven, Zeebrugge, Belgium (51.21N, 03.11E).

AH6, born in the colony Maasvlakte, the Netherlands (51.59N, 04.02E). AH6 was ringed as pullus on July 20 1992, now in 12cy and believed to be a hybrid Yellow-legged Gull (michahellis) x Herring Gull (argenteus). 2002 and 2003 AH6 was paired with blue BWAD, probably ringed as pullus at Zeebrugge, Belgium, summer 1999. BWAD is a male, aggressive in defending its territory at the colony of Zeebrugge and this individual shows only very little black markings on both upper mandible and the cutting edge of the lower mandible. The iris is clear yellow. This couple nicely demonstrates the migration of LBBG from the Netherlands to the growing colony of Zeebrugge.

03 May 2003

AH6 was rediscovered on two occasions winter 2001-2002 and 2002-2003 in southern France, as the website of Alain Fossé shows:

date:	place of rediscovery:	coordinates	distance
24·12·01	la Courtrie/Le Louroux-Béconnais	47.30N, 00.54W	609 km
10·01·03	la Petite Guibarderie/La Chapelle-Hullin	47.45N, 01.05W	596 km

Alain questions if it is a "Goéland argenté x Goéland leucophée", a hybrid Larus argentatus x Larus michahellis? In his opinion, the mantle colour is darker than nearby YLG in southern France, as if there is a fuscus influence. But according to the ringer, Norman Van Swelm, the mother has been a michahellis YLG and was as dark as the birds of the West Iberian population. AH6 was identified on its breeding ground as a Yellow-legged Gull Larus michahellis! This doesn't match the current idea at the colony of Zeebrugge, where AH6 proofed to be much darker than michahellis, reminiscent of graellsii from western populations in the U.K. It's interesting to see if it really has been a male Herring Gull in stead of a male Lesser Black-backed Gull, who is the father.
AH6 was caught by Gérard Séjourné and released on 24th December 2001 on the rubbish dump of Le Louroux-Béconnais (Maine-et-Loire, France);
it was entangled in plastic bags and exhausted. Alain continues: it has nested, in at least 2001 at Zeebrugge (Belgium), by then already paired with a male Lesser Black-backed Gull Larus fuscus, colour-ringed blue BWAD.

10 January 2003

On January 10 2003, Alain Fossé and Franck Noël watched the bird at the La Chapelle-Hullin landfill, Maine-et-Loire, France (47.45N, 01.05W), some km's north of the original landfill it was found strangled. They were puzzled by the mantle colour of the bird, which was obvious darker than michahellis and made them think of a 'pale graellsii'. The head was immaculate white as in michahellis and the legs were pinkish-yellow. They wondered if this mantle colour could fit it a hybrid which parents are are both paler, i.e.: can this be a hybrid michahellis x argenteus?

Chris Kehoe (from Tynemouth, U.K.) responded on January 11 2003:
Thanks very much for posting this picture of a most interesting bird. Unfortunately the second link you provided does not seem to be working. Are there any images of the open wing of this bird available? (On which Alain responded: no, there are no other images).
The mantle tone is confusing and I cannot explain how a hybrid Herring X michahellis Yellow-legged Gull can have a mantle tone darker than either parent. I suspect that this bird might have been thought to be an Atlantic Yellow-legged Gull if it had not been ringed, although perhaps the white primary tips are a little too large and fresh looking.
Does anyone on this list have any recent information about the frequency of hybrid pairs of large gulls in W Europe. I do know that a bird originally identified as a Yellow-legged Gull was found breeding with a Herring Gull on the Farne Islands (NE England) recently. However, it was ringed and was found to have been reared on the Isle of May (SE Scotland) several years earlier so seems very unlikely to have been a pure Yellow-legged Gull and may actually have been a Herring X Lesser Black-backed Gull. I know too that hybrid pairs have been regularly reported in the Netherlands but I have no information about precise numbers. There are quite a number of images of suspected or known hybrids on the internet now but these do not really give a good indication of how frequently hybridisation is occurring .Does anyone know how frequent hybrid pairs of Herring X Lesser Black-backed Gulls are relative to hybrid pairs of either of these species with apparent Yellow-legged Gulls?
The hybrid issue is probably not a major identification problem in areas where Yellow-legged Gulls are of relatively frequent occurrence but in more northern areas where these birds are very scarce (and where hybrids may be more likely to occur - perhaps involving any combination of Herring. Lesser black-back and Yellow-legged Gull) the problem has perhaps been underestimated.

Nick Rossiter responded as well:
An interesting bird. But how do we know who its parents were? If it were ringed in a colony, surely it is difficult to know the parents of a particular gull. Even presumed parents may not be the actual parents, unless they are 100% faithful. So I would say this is a presumed hybrid unless Norman can persuade otherwise.
It's difficult to assess the leg length from the photo but they do look on the long side for atlantis. The bill is also rather long for atlantis. The head, bill and orbital ring look fine for michahellis as does the dull grey tone (grey-blue in atlantis). Even if it has got something else in it, michahellis looks to be the dominant component in the structure. How reliable is the mantle shade? The primary tips seem larger than those normally found in michahellis, even when fresh. Are there any comments on this from people in the michahellis breeding areas?

Rafael Saiz Elizondo can tell more about the situation in Basque Country: the only autochthonous large gull species was Larus michahellis, but in the last 20 years Larus fuscus graellsii has spread along some colonies. Here, hybridisation is quite common, but Rafael has no description on hybrids.

It indeed is very problematic to pin down the true parents in a colony like the one at Maasvlakte, with numerous possibilities for cross-breeding. There are over 35.000 breeding pairs with at least over ten mixed couples michahellis x argenteus and michahellis x graellsii. Further north, mixed breeding occurs in the colony of IJmuiden (michahellis x graellsii) and further south mixed pairs have been recorded at Neeltje Jans, Zeeland, the Netherlands (michahellis x argenteus) and several mixed pairs have been found recently at Zeebrugge (michahellis x graellsii). Last year, 2002, one pure couple of michahellis managed to raise chicks at Zeebrugge.

Links:

*YLG (L. michahellis michahellis) 13⁺cy CU9& adult LBBG,* Missouriweg - Maasvlakte, the Netherlands, May 12 2002 (51.59N,04.02E). One of the few mixed pairs at Maasvlakte.
possible hybrid Herring Gull x Lesser Black-backed Gull (2cy argentatus x fuscus), October-December 1999, Westkapelle, the Netherlands (51.33N-03.25E). Pictures by Pim Wolf.
*possible hybrid Herring Gull x Yellow-legged Gull EP29(4cy argenteus x michahellis), April 02 2000, Neeltje Jans, the Netherlands. Picture by Pim Wolf. Probably a known hybrid, born in the Netherlands in the colony of Neeltje Jans. EP29 was born in 1997 and ringed June 23, offspring of a true male michahellis, ringed orange EAY8 and a female argenteus*. However, remember that theoretically another male could be the father.
*possible hybrid Herring Gull x Yellow-legged Gull EP30(3cy argenteus x michahellis)*, November 07 1999, Westkapelle, the Netherlands (51.33N-03.25E). Picture by Pim Wolf. Probably a known hybrid, from the same nest as EP29. Remember that theoretically another male could be the father.
*possible hybrid Herring Gull x Yellow-legged Gull EV65 (4cy argenteus x michahellis),* April 02 2000, Neeltje Jans, the Netherlands. Picture by Pim Wolf. Probably a hybrid, born in the Netherlands in the colony of Neeltje Jans. As soon as data are available, more information about this bird will be added.
*possible hybrid Herring Gull x Yellow-legged Gull (3cy argenteus x michahellis),* November 28 1999, Westkapelle, the Netherlands (51.33N-03.25E). Pictures by Pim Wolf.
*possible hybrid Yellow-legged Gull x Lesser Black-backed Gull (adult michahellis x graellsii),* September 22 2002, Boulogne-sur-Mer, France. Note the short bill, the extensive bold streaking on the head and the delayed moult timing compared to michahellis.