Urbanization mechanisms in bird species: population systems transformations or adaptations at the individual level?
Division of High Plants, Biological Faculty of Lomonosov Moscow State University
Leninskie Gory, 119992 Moscow
e-mail: wolfl7@list.ru
The present research deals with urbanization of wild bird and mammal species. Forms and mechanisms of population steadiness in the urban landscape have been examined. The urbanization process turned out to be a directed change of the population system forming de novo in the urbolandscape leading to a sustainable organization peculiar for the particular environment. The population organization of different types in urbolandscape is found to provide its stability under conditions of directed and fast changes accompanied with instability and heterogenous structure of habitats. It is shown that the same type of population organization meets the corresponding demands among different species settling in the urban environment. Its features are "openness" and "flowage" of the groups, far order of settlement levels and other units of population system, constant movements of the individuals between the groups as a respond to the signals of urboenvironment significant changes. The "urban" variant of the population system organization turns out to be opposite to that of the same species in the non-urban habitats. After formation of the urban types by the species and successful developing of the town, the urban population becomes separated from the maternal local population and begins to exist independently in the urban landscape. The variety of adaptation aberrations in ecology, behavior, and mode of life of urban birds is the population system stability function in the urban landscape and is not a result of individual selection. It is shown that the urbanization process of the species goes firstly on the population level being the system structure transformation developed by the species towards the most stable state in the town (city) territory. Only after the appearance of stable urban population, the urban individuals show the rapid growth of different changes in ecology, behavior, mode of life that was traditionally described by naturalists as species adaptation to the city conditions. The key features of urban population stability/instability are described. Their application to closely related species allows us to distinguish potential urbanists from unstable and vulnerable species that could be soon pushed out of the city. The application of corresponding criteria to the urban populations of such species constituting one guild allows us to predict if their developing in the given town would be successful or unsuccessful. The latter is very important since close species are, as a rule, ecologically indistinguishable in the urbanized landscapes. So one can not predict successful/unsuccessful urbanization taking into account the differences in the range of habitats, breeding success, and other external features.
