Great Black-backed Gull (Larus marinus)

(last update: July 12, 2015)

Great Black-backed Gull 4cy December

Plumage variation in 3CY and 4CY marinus for period September-December.

3CY BIRDS

Larus marinus 3CY JH617, October 04 2013, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Ringed as pullus in 2011 in Norway. Retarded looking bird with many barred coverts. Combined with adult-like central primaries with bold white tips on P5-P6.	Larus marinus 3CY, September 20 2015, IJmuiden, the Netherlands (Mars Muusse). Typical combination of adult-like new 3rd gen secondaries and many immature marked coverts and black in 3rd gen tail. In 2CY birds the new P10 has an indistinct mirror; here, in 3rd gen P10 the mirror is sharply borbered and normally with a full sub-terminal band (which will no longer be present in 4th gen P10).
Larus marinus NLA7105682 3CY, September 24 2014, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Ringed as pullus in 2012 in the Netherlands. Adult like pattern on central primaries indication too advanced for 2nd gen; small tips on P7-P9 far too small for 4CY birds. Several barred coverts.	Larus marinus 3CY, September 24 2015, IJmuiden, the Netherlands (Mars Muusse). Typical combination of adult-like new 3rd gen secondaries and many immature marked coverts and black in 3rd gen tail. 3rd gen P10 has the mirror sharply borbered and with a full sub-terminal band.
Larus marinus 1LC 3CY, November 02 2013, Dublin, Ireland (Graham Prole). Ringed as pullus in 2011 in Ireland. Bold white tips on all outer primaries and adult-like secondaries. Still faded brown hue on many coverts.	Larus marinus 3CY, December 20 2014, IJmuiden, the Netherlands (Mars Muusse). Adult-like secondaries, inner and central primaries. Still, many immature patterned coverts and less white in wing tip (P6-P10) than full adults have, e.g. this bird has full subterminal band on P10.
Larus marinus DKC3092175 3CY, September 24 2012, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Ringed as pullus in 2010 in Denmark. Advanced plumage, with very bold white tips on outer primaries and almost completely jet-black plumage very like 4CY birds. Much black on bill but this still may match 4CY birds.	Larus marinus 3CY, December 20 2014, IJmuiden, the Netherlands (Mars Muusse). Adult-like secondaries, adult-like inner and central primaries and mirror on P9 and P10. Still, many immature patterned coverts and less white in wing tip than full adults have.

4CY BIRDS

Larus marinus JZ84 4CY, September 10 2010, Westkapelle, the Netherlands (Theo Muusse). Ringed as pullus in 2007 in Norway. By September, old flight feathers are useful for ageing: adult-like old P9 and P10 should be 3rd gen, combined with black in the old tail and some brown coverts.	Larus marinus 4CY, September 20 2015, IJmuiden, the Netherlands (Mars Muusse). By September, old flight feathers are useful for ageing: old 3rd gen P10 with large white tip. Still some brown coverts. Black on bill.
Larus marinus DKC3092175 4CY, November 22 2013, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Adult-like with obvious black on the bill.	Larus marinus 4CY, December 20 2014, IJmuiden, the Netherlands (Mars Muusse). Adult-like with single brown coverts (see underwing).
Larus marinus JE580 4CY, October 04 2013, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Ringed as pullus in 2010 in Norway. Moult score: P7/-. Full band on the bill.	Larus marinus 4CY, December 20 2014, IJmuiden, the Netherlands (Mars Muusse). Large mirrors on P9 and P10. Several brown coverts and broad bill-band.
Larus marinus 76D 4CY, November 15 2012, Boulogne-sur-Mer, France (Jean-Michel Sauvage). Ringed as pullus in 2009 in France. Much adult-like in plumage. This limited black on the bill is no safe criterion for ageing, also occurs in mature birds.	Larus marinus 4CY, December 20 2014, IJmuiden, the Netherlands (Mars Muusse). Adult-like with single brown coverts (see underwing) and most obvious broad bill band. Immature birds have a tendency to develop more streaking on head and breast than wintering adults do.