The Strange World of Gull Identification Nick Rossiter


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The Strange World of Gull Identification

  • Nick Rossiter

  • October 2001


Great Advances

  • Moult much better understood

  • All ages considered

  • Seasonal changes dealt with

  • Much more information on Herring Gull/LBB complex world-wide:

    • accounts of Mediterranean YLG, Caspian Gull, Baraba Gull, Mongolian Gull, American Herring Gull


Problems

  • Later!!



















Grey-headed Gull Adults, Gambia, August 1999



Moult in Large Gulls

  • Juveniles: (first-generation)

    • scapulars, back, coverts (post-fledging)
  • First-winter: (second-generation)

    • scapulars, back, coverts (continuous)
    • primaries (spring, summer)
  • (First-summer -- fading, bleaching)

  • Second-winter (third-generation)



Timing is Very Variable

  • Northern forms (e.g. Scandinavian argentatus, Glaucous Gull) may retain juvenile feathers to late winter or spring

  • Southern forms (e.g. Mediterranean Yellow-legged Gull) moult many juvenile feathers in late summer/ early autumn

  • Primary moult seems more independent of latitude



Juvenile ‘Yellow-legged Gull’ La Linea August 2001



Juvenile ‘Yellow-legged Gull’ Estepona August 2001



‘Caspian Gull’ Norway, First-winter, February 2001 (Frode Falkenberg)



‘Caspian Gull’ Norway, First-winter, February 2001 (Frode Falkenberg)



First-winter ‘Yellow-legged Gull’ San Sebastian, February 2000 (Dick Newell)



Matosinhos, First-winter/1s ‘Yellow-legged Gull’, April 2001



First-winter/1s ‘Yellow-legged Gulls’ (with 2s LBBG), Porto, April 2001



First-winter/1s ‘Yellow-legged Gull’ Fuerteventura, April 1999



Four First-summer ‘Yellow-legged Gulls’ Fuerteventura, April 1999



Two first-summer/2w Yellow-legged Gulls michahellis Royan, August 1991



First-summer ‘Yellow-legged Gull’ Lanzarote, August 1992



First-summer/2w ‘Yellow-legged Gull’ Lanzarote, August 1992



First-summer/2w ‘Yellow-legged Gull’ Lanzarote, August 1992



First-summer ‘Yellow-legged Gull’, Tenerife, July 2000



First-summer/second-winter ‘Yellow-legged Gull’ Estepona August 2001



First-summer/second-winter ‘Yellow-legged Gull’ Estepona August 2001



Second-winter ‘Yellow-legged Gull’ Fuerteventura, September 2000



Second-summer ‘Yellow-legged Gull’ Porto, April 2001



Second-summer ‘Yellow-legged Gull’, Essaouira, April 2000



Second-summer ‘Yellow-legged Gull’, Essaouira, April 2000



Third-winter ‘Yellow-legged Gull’, Gran Canaria, September 2000



Fourth-summer ‘Yellow-legged Gull’, Matosinhos, April 2001



Adult summer ‘Yellow-legged Gull’, Agadir, April 2000



Part 2

  • Forms of Yellow-legged Gulls



Adult Mediterranean michahellis, Royan, August 1991



Adult Mediterranean michahellis, Royan, August 1991



Adult Mediterranean michahellis, Royan, August 1991



Adult/3s-4w Mediterranean michahellis, Royan, August 1991



Adult/3s-4w Mediterranean michahellis, Royan, August 1991



Two first-summer/2w Mediterranean michahellis Royan, August 1991



Map for Atlantic Forms





Adult ‘Yellow-legged Gull’ atlantis, Tenerife, August 1998



Adult ‘Yellow-legged Gull’ atlantis, Tenerife, December 1996



Adult ‘Yellow-legged Gull’ atlantis, Lanzarote, August 1992









Juvenile ‘Yellow-legged Gull’ atlantis, Tenerife, August 1998



Three Adult Atlantic Yellow-legged Gulls, Agadir, April 2000



Typical Adult Wingtip ‘Yellow-legged Gull’, Agadir, April 2000



Typical Adult Wingtip ‘Yellow-legged Gull’, Fuerteventura, April 2000





Comparative Wingtip Data

  • None available from core area of Mediterranean Yellow-legged Gull in western Mediterranean

  • Some data from putative michahellis in northern Europe.

  • Are northern European birds typical?

  • Birds of known origin are emphasis of current work (e.g. IGM V)



Adult ‘Yellow-legged Gull’, Faro, March 1999



Two Adult ‘Yellow-legged Gull’, Setubal, March 1999



First-winter/1s ‘Yellow-legged Gulls’ (with 2s LBBG), Porto, April 2001



Matosinhos, March 2001, smithsonianus, intermedius, graellsii, ‘YLG’



Matosinhos, March 2001, YLG’ adult, ‘Big Waters Gull’.



Part 3



Porto, March 2001, Pair YLG’ adults



Minho, April 2001, YLG’ adult



Noja (Santander), August 1990, 3s YLG’



San Sebastian, February 2000, ‘YLG’ adult (Dick Newell)



San Sebastian, February 2000, ‘YLG’ adult (Dick Newell)





Map showing Areas for Forms



‘YLG’: Mauritania, Azores; Kelp Gull (Birding World)



Separating dark form from michahellis



Intersection Area -- Atlantic / Mediterranean

  • Do they mix?

  • Do the breeding areas overlap?

  • Are there intermediate forms?





Tanger, August 2001, Adult ‘YLG’



Tarifa, August 2001, Adult ‘YLG’



Tarifa, August 2001, Two Adult Mediterranean YLG



Comparison Med/Atlantic YLG adults, Conil, August 2001



Conil, west Andalucia



Gibraltar from La Linea



Gibraltar, June 1994, Adult + chick ‘YLG’ (Tom Cadwallender)



Estepona, east Andalucia



Estepona, August 2001, Adult ‘YLG’



Estepona, August 2001, 2s/3w ‘YLG’



Estepona, August 2001, ad + imm ‘YLG’



Strange World?

  • Because too many id criteria rely on studies of migrants to northern Europe, rather than of populations in their native areas.

    • Such migrants are putative
    • Main forms described but variation cannot be determined reliably
    • Even marked/ringed individuals may not be typical of the ones that stay at home


Current situation

  • Difficult

  • Forthcoming BB paper based on studies of populations to the east rumoured to question id of Caspian Gull

  • Work to the west (as here) shows definition and id of Western Yellow-legged Gull to be far from settled



The End

  • of the Seagull Story




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