▁America . ▁It ▁was ▁previously ▁considered ▁cons pec ific ▁with ▁the ▁yellow - fo oted ▁g ull ▁( Lar us ▁liv ens ) ▁of ▁the ▁G ulf ▁of ▁California . ▁The ▁western ▁g ull ▁ranges ▁from ▁British ▁Columbia , ▁Canada ▁to ▁B aja ▁California , ▁Mexico . ▁ ▁Description ▁ ▁The ▁western ▁g ull ▁is ▁a ▁large ▁g ull ▁that ▁can ▁measure ▁ ▁in ▁total ▁length , ▁sp ans ▁ ▁across ▁the ▁wings , ▁and ▁we igh s ▁. ▁The ▁average ▁mass ▁among ▁a ▁survey ▁of ▁ 4 8 ▁g ull s ▁of ▁the ▁species ▁was ▁. ▁Among ▁standard ▁measurements , ▁the ▁wing ▁ch ord ▁is ▁, ▁the ▁bill ▁is ▁ ▁and ▁the ▁t ars us ▁is ▁. ▁The ▁western ▁g ull ▁has ▁a ▁white ▁head ▁and ▁body , ▁and ▁gray ▁wings . ▁It ▁has ▁a ▁yellow ▁bill ▁with ▁a ▁red ▁sub term inal ▁spot ▁( this ▁is ▁the ▁small ▁spot ▁near ▁the ▁end ▁of ▁the ▁bill ▁that ▁ch icks ▁pe ck ▁in ▁order ▁to ▁stim ulate ▁feed ing ). ▁It ▁closely ▁res emb les ▁the ▁sl aty - back ed ▁g ull ▁( Lar us ▁sch ist is ag us ). ▁In ▁the ▁north ▁of ▁its ▁range ▁it ▁forms ▁a ▁hy brid ▁zone ▁with ▁its ▁close ▁relative ▁the ▁gla uc ous - wing ed ▁g ull ▁( Lar us ▁gla u ces c ens ). ▁Western ▁g ull s ▁take ▁approximately ▁four ▁years ▁to ▁reach ▁their ▁full ▁pl um age , ▁their ▁layer ▁of ▁fe athers ▁and ▁the ▁patterns ▁and ▁colors ▁on