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2 Polish Journal of Ecology

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Plumage polymorphism and breeding parametres of various Feral Pidgeon (Columbia livia Gm.) morphs in urban area (Gdańsk, North Poland)

Hetmański T., Jarosiewicz A.

Polish Journal of Ecology

2008

Vol. 56, nr 4

683-691

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 km[^2]) 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 km[^2]) . 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.

The effect of environmental factors and nesting conditions on clutch overlap in the Feral Pigeon Columba Livia f. urbana (Gm.)

Hetmański T., Wołk E.

Polish Journal of Ecology

2005

Vol. 53, nr 4

523-534

Clutch overlap is a reproductive strategy of the Feral Pigeon, which results in an increase in the number of clutches produced by a pair and, as follows, an increase in the number of young raised. It is dependent on the length of time the clutch is cared for and the length of the interval between clutches. Both these component elements of clutch overlap are directly affected by environmental conditions, such as the length of day and ambient temperature. The duration of clutch care and the clutch interval were distinctly shorter in the warmer part of the year with a longer day than during the fall and winter. We believe that ambient temperature has a significant effect on the length of the clutch interval, as it is a decisive factor in the achievement of thermoregulation ability in the nestlings. Earlier achievement of this ability by nestlings in higher ambient temperatures (at Ta = 21.5°C, normothermy appeared in the 6th to 7th post-embryonic day in the life of nestlings, while at Ta = 19.5°C - in 8-9 days) allows both parents to forage for longer periods of time and to start a new breeding cycle earlier. We confirmed that nesting conditions (the number of nests in a breeding pair's territory, brood size and location of the nest in the colony) also influenced the duration of clutch care and the length of clutch interval, and therefore, the degree of clutch overlap. The clutch interval was shorter when parents only cared for one young, than when two young were in the nest. Breeding pairs with large territories that included two nests had shorter clutch intervals than those pairs with only one nest. Young raised in nests located close to egresses left the colony more quickly than young in nests farther away.