THE IMPACT OF CHANGES IN BREEDING CONDITIONS IN THE ARCTIC ON THE EXPANSION OF THE RUSSIAN POPULATION OF THE BARNACLE GOOSE (BRANTA LEUCOPSIS)

摘要

In the 20th century, the breeding grounds of the Barnacle Goose over the territory of Russia included only the Novaya Zemlya Archipelago and the Vaygach Island. Until the middle of the century, the population did not exceed 20-30 thousand individuals. In the 1970's to 1980's, the numbers of the Barnacle Goose started increasing slowly. Shortly after that new colonies appeared in the coastal areas of the Barents Sea, ranging from the Kanin Peninsula to the Khaypudyr Bay, Kolguev Island. By 2017, the population numbers reached about 1.2 million individuals. The growth of the Barnacle goose population has coincided with the phase of a pronounced temperature increase and of climate warming in the Arctic. The mean annual temperatures have increased significantly in the Eastern European tundra. A simultaneous decrease in the ice cover in the Barents Sea has led to spreading the warm Atlantic waters much further to the east in modern conditions and thus rendering a heating effect extending as far as the Kara Sea. One of the consequences has become a steady decrease in weather differences between the western and eastern areas of the region. The climate in the eastern areas, the Vaygach Island and the Yugor Peninsula in particular, becomes milder and is changed relatively faster. This is believed to have been one of the reasons for the vast expansion of the Barnacle Goose to the east and the establishment on the Kolguev Island. In the spring period, in May and June, the average daily temperatures in the Eastern European tundra have undergone no significant change during the last 35 years, but taking into account the lack of a pronounced temperature increase, the transition of the mean daily temperature over 0 degrees C has shifted to a much earlier period. Throughout the territory of the Eastern European tundra, the cumulative temperature of the summer period has increased along with the length of the period with positive temperatures. These factors combined have led to a prolonged vegetation period and a phytomass growth. This trend is most pronounced in the post-hatching period, i.e. July and August. The prolongation of the active vegetation period offers young Barnacle geese additional advantages in one of the most crucial periods of their life, i.e. the fledging period and the preparation for migration. Currently, the geese leave their nesting areas later. This allows not only the fledglings to become strong enough for a lengthy flight, but also the geese, due to good food and a significant accumulation of fat reserves on the breeding grounds, for using fewer migration stops on the flyway in autumn and thus avoiding areas with strong autumn hunting pressure. All these factors combined seem to have allowed for new habitats on marshes and in the typical plain tundra to be used by Barnacle geese, leading to a significant increase in the numbers of the species. More detailed information obtained now fails to support the hypothesis stipulating the adverse impact of a phenological mismatch on the Barnacle Goose. The species continues demonstrating a steady population growth, the numbers increasing not only in the newly-established habitats and regions, but also in traditional nesting areas. There are 1069107 +/- 37655 Barnacle geese estimated to presently populate the Russian part of its range (excluding the Novaya Zemlya Archipelago).