Dynamics of Habitat Distribution in Birds Differing in the Level of Site Tenacity

The dynamics of habitat distribution in two bird species differing in the level of site tenacity—willow warbler (relatively tenacious) and little bunting (more flexible)—were studied at the boundary of the northern taiga and forest–tundra zones over ten years. The distribution pattern proved to be more uniform in the willow warbler than in the little bunting. Both species occupied their habitats according to a well-known scheme: initially, the birds settled in their favorable floodplain habitats and later; when their abundance increased, in less preferable habitats (terraces above the floodplain, moss bogs, and the tundra). In the case of willow warbler, the process of occupying the floodplain was stepwise: bird density increased sharply, remained at the same level in the next year, then increased again, etc. In the case of little bunting, the degree of floodplain occupation by birds remained high, except for the years when high spring floods interfered with bird settling.     

Spatial differentiation of the total bird population in a definite area

The spatial structure of the total bird population at the level of communities has been studied in a definite area at the boundary between northern open forests and forest-tundra. The boundaries of communities have been delimited by mapping out areas with a homogeneous species composition. The pattern of communities is shown to be as follows: the species-richest part of a local species assemblage (characteristic of a given landscape type) forms the basic community, which is surrounded by poorer communities of increasingly variable composition and configuration, depending on distance from the basic community. The most distant communities consist almost exclusively of abundant and widespread species. A group of borderline communities of mixed composition is located at the boundary between two landscape complexes. Mechanisms accounting for such a pattern are discussed.     

Intraspecific Differentiation of the Oriental Cuckoo (Cuculus optatus) within the Range: Relationship with the Abundance of Host Species

Russian Journal of Ecology - The distribution of C. optatus host-specific races within the breeding range has been analyzed. It has been found that these races are geographically separated: their...     

Status and trends of tundra birds across the circumpolar Arctic

Tundra-breeding birds face diverse conservation challenges, from accelerated rates of Arctic climate change to threats associated with highly migratory life histories. Here we summarise the status and trends of Arctic terrestrial birds (88 species, 228 subspecies or distinct flyway populations) across guilds/regions, derived from published sources, raw data or, in rare cases, expert opinion. We report long-term trends in vital rates (survival, reproduction) for the handful of species and regions for which these are available. Over half of all circumpolar Arctic wader taxa are declining (51% of 91 taxa with known trends) and almost half of all waterfowl are increasing (49% of 61 taxa); these opposing trends have fostered a shift in community composition in some locations. Declines were least prevalent in the African-Eurasian Flyway (29%), but similarly prevalent in the remaining three global flyways (44–54%). Widespread, and in some cases accelerating, declines underscore the urgent conservation needs faced by many Arctic terrestrial bird species.     

Formation of the spatial structure of bird populations as exemplified by the willow warbler and little bunting,species differing in site fidelity

The formation of the spatial structure of the willow warbler (Phylloscopus trochilus) and little bunting (Emberiza pusilla) populations differing in the degree of site fidelity was studied. The area populated by each species was subdivided according to how regularly its parts had been populated over a 16-year period and how synchronous the population dynamics were. The validity of some hypotheses detailing the population formation was tested by comparing simulated population dynamic curves in segments differing in quality with actual curves.     

Anthrax in Yamal: An ecological view on traditional reindeer husbandry

The critical situation with traditional reindeer husbandry in the Yamal district of the Yamalo- Nenets Autonomous Area, indicated by an anthrax epizootic, is analyzed from an ecological viewpoint. The phenomenon of epizootic is regarded as an ecosystemic homeostatic mechanism operating to prevent excess population growth and maintain ecosystem integrity. The shutdown of this mechanism by means of vaccination, with the proportion of reindeer removed from slaughter remaining low, has resulted in an increased grazing load of rangelands and their consequent severe degradation. These events have been aggravated due to change in the type of ownership in reindeer husbandry during the reforms of the 1990s. The ecological situation is classified as critical, posing a real hazard to this particular ethnic form of economy. It is concluded that the period of extensive/expansive development of Yamal reindeer husbandry has come to an end. Sociopsychological attitudes of the Nenets, acquired when biological resources were abundant, contradict with the principles of ecosystem existence and functioning in the period of resource depletion. The maintenance of reindeer husbandry in the traditional form requires increasing material, labor, and financial investments, but positive results are unlikely to be obtained because of ecological constraints.