Birds in Bulgaria

L 54-60 cm, WS 123-148 cm. Very common near coasts; frequent inland, too, feeding on fields, rubbish dumps, etc. Roosts on harbour piers or secluded islands; flights to these at height, often in formation. Frequently soars high up. Nests, often colonially, on coastal islands, cliffs or at lakes.
IDENTIFICATION: Four age-groups (see p. 168). Told from all other common gulls by large size and pale grey upperparts (cf. much smaller Common Gull, p. 172), but see very similar Yellow-legged Gull. Grey on upperparts develops only from 2nd-winter onwards, so ‘all-brown’ 1st-years more difficult to tell from Lesser and Great Black-backed Gulls (p. 176). Head of adult white in summer, streaked in autumn. Bill colour develops gradually, from dark with variable pale base on juvenile/1st-winter to yellow with orange-red spot on adult; iris from brown of juvenile to yellow (with yellow or orange orbital ring) of adult. Legs pink at all ages. See Great Black-backed Gull (p. 176) for general comments on ageing large gulls. - Variation: Birds of W Europe and Iceland (ssp. argenteus) are relatively small and round-headed and have back pale grey. Breeders in Scandinavia and around the Baltic (argentatus), wintering partly in W Europe, average larger, slightly darker grey on back, extremes having little black and much white on wing-tip; birds of E Baltic and N Fenno-Scandia like argentatus, but locally some or most have legs yellowish or yellow (var. ‘omissus’).
VOICE: Calls include strident ‘kyow’, repeated and loud when used as alarm. In anxiety a distinctive ‘gag-ag-ag’. Familiar exalted ‘laughing’ display-call is a loud, deep and clanging ‘aau … kyyaa-kya-kya-kya-kya-kya kya … kyau’. Yellow-legged Gull