In 2007, the population of Feral Pigeons in Gdańsk City (almost 500,000 inhabitants) constituted 14 200 individuals. The population density in the built-up areas of Gdańsk (82.2 km²) was estimated at an average of 17.2 birds 10⁻¹ ha, however the highest density occurred in Gdańsk’s city centre area (5.7 km²) – 44 birds 10⁻¹ ha. Blue plumage type pigeons dominated in the population (93%), while black, red and albinotic types were rarely observed. Melanistic birds were more frequently found than blue-bar birds, whose plumage is inherited from the Rock Pigeon. However, blue-bars were more numerous in Gdańsk compared with other pigeon populations in central and northern Europe. Old pre-war buildings were not confirmed as influencing the plumage pattern of pigeons. Melanistic birds were more numerous in old district of Oliwa, whereas blue bars in old Gdańsk city centre. The plumage of pigeons in small flocks of up to 50 birds did not differ from that of pigeons in flocks of over 50 and 100 birds. Blue-bars, checkers and dark checkers did not differ in body mass or breeding parameters. Other causes of polymorphism variation among pigeons in a population are discussed.