Great Black-backed Gull (Larus marinus)
(last update: July 12, 2015)
Great Black-backed Gull 4cy April
Great Black-backed Gull (Larus marinus) 1LC 3CY-5CY, November 2013 - May 2015, Howth & Bullock Harbour, Dublin, Ireland. Picture: Graham Prole.
Great Black-backed Gull (Larus marinus) 1MC 3CY-4CY, April 2014 & 2015, Howth, Ireland. Picture: Graham Prole.
Great Black-backed Gull (Larus marinus) 1UK 3CY-4CY, April 2014 - July 2015, Howth, Ireland. Picture: Graham Prole.
Great Black-backed Gull (Larus marinus) 4CY, April 07 2017, IJmuiden, the Netherlands.
Great Black-backed Gull (Larus marinus) 4CY, April 08 2017, IJmuiden, the Netherlands.
Great Black-backed Gull (Larus marinus) 4CY, April 07 2017, IJmuiden, the Netherlands.
Great Black-backed Gull (Larus marinus) 4CY, April 29 2017, Katwijk, the Netherlands.
Great
Black-backed Gull (Larus marinus) sub-adult: April 2001, IJmuiden, the Netherlands (52.27
N, 4.33 E). An
individual much like an adult, but the black marking on the upper mandible
may be indicative for near-adultness. 
Great
Black-backed Gull (Larus marinus) sub-adult: May 17 2002, Le
Portel - Boulogne sur Mer, France (50.42 N - 01.34 E). The large white
tips on the dark centred secondaries and the conspicuous white mirror on
p10 rule out a 3cy bird in spring. The abraded brown greater coverts, the
black shaft in the outer tail-feathers, the black bill-band and the very
immature primary coverts make it very unlike to be in 5cy already.