Arctic Geese (Anser) and Brants (Branta) of Eurasia: An Analysis of Factors That Control Population Dynamics and Geographical Ranges

摘要

Geese (Anser) and brants (Branta) are important elements of Arctic ecosystems, which attract the interest of biologists around the world. Due to this interest, a great amount of empirical data has been accumulated, including detailed descriptions of the morphology, nesting characteristics, trophic ecology, behavior, migrations, population geography, and other features of Arctic geese and brants. The extent of their range along the Arctic coast of Eurasia largely depends on population size. Therefore,all of the factors influencing population size also indirectly affect the range extent. Geese and brants species significantly differ in population size, range extent, and tendencies in their changes over time. We compared the available data in order tofind out what, in which way, and to what extent determines the population size and range extent in geese and brants. The main contribution to a reduction in population size is made by extermination at nesting sites and along the flyways and the lack offood at overwintering sites. The species that do not use cultivated plants in winter are small population size. The next most significant factor is the feeding type, which is determined by body size and the ratio between beak length and head length. Thepopulation size is influenced much less by all other factors related to patterns of feeding and nesting. The absence of a signifcant effect of these characteristics on the population size and range of geese and brants may be interpreted as the result ofanthropogenic impact, which does not yet seem to be able to be estimated quantitatively. The disappearance of geese and brants within considerable areas in the Arctic Region may cause serious ecological consequences.