Great Black-backed Gull (Larus marinus) Science Article 1
Until now 59 Great Black-backed Gulls have been recorded on the territory of Bulgaria, mainly during the seasonal migrations and in winter. They prefer the sea coast, seldom they visit the inland reservoirs. The first autumn migrants reach the Black Sea after September 6th. A new wave of migration is observed in December due to spell of cold weather in the northern wintering grounds. The birds leave for their breeding grounds in March and April. Non-breeding individuals remain on the Bulgarian reservoirs in summer.
D.N. Nankinov, Berkut. 9 (1-2). 2000. P. 47-50