Wyniki wyszukiwania - BazTech

1

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

EN

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.

2

The timing of fledging and annual post-fledging survival of juvenile Feral Pidgeons (Columbia livia) in a city area (NW Poland)

Hetmański T.

Polish Journal of Ecology

|

2007

|

Vol. 55, nr 2

367-375

EN

Research on the annual post-fledging survival of young Feral Pigeons Columba livia was conducted in 1998-2001 in five breeding colonies located in the city centre of Słupsk (NW Poland, area 43 km[^2]. Breeding pairs and their offspring were individually ringed. A total of 1016 clutches were studied, as was the fate of 809 fledglings. It was found that although fledglings were produced throughout the entire year, about 81-93% of young was leaving the nest in the period between April and September. The peak period of fledging occurred in May, August or June accordingly in successive study years. The dynamic of fledging in one year reflected the pairs. egg laying activity occurring two months earlier. Juvenile mortality was highest during the first month after fledging and was found to be 45% of young birds. The main cause of death was hunger, as the young, inexperienced individuals were unable to compete successfully with adults for food at foraging areas. Loss of young clearly decreased with every successive month. The annual survival rate of juveniles produced in a calendar year was 30%. Almost all the juveniles surviving their first year of life joined the breeding population. Young produced in winter and spring had better survival rates than did those leaving the nest in summer, and especially, in autumn. The differences in survival rates found among the seasons of the year most likely resulted from changes in the pressure of competition for food in foraging areas.

3

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

EN

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.