Hybrid
1st winter hybrid Glaucous Gull x Glaucous-winged Gull or Vega Gull?
Choshi Chiba Japan, February 26th 1994
Another 1st winter hybrid, Glaucous Gull x Vega Gull? 

Left hand bird is  1st winter Slaty-backed Gull
Slaty-backedXGlaucous-winged Back