Dynamics of distribution area, abundance, and breeding of common crane Grus grus in Eastern Siberia

The article deals with the features of distribution and ecology of the common crane in Eastern Siberia (Irkutsk Oblast, Buryatia, Zabaikalsky Krai). The data were obtained during 1968-2017. In the region of the study the common crane is a usual breeding species with a small population number and very uneven distribution. It nests in wetlands of river flood-plains and depressions of large lakes, or extensive systems of small lakes, often in close proximity to human settlements. Since there are a lot of territories suitable for the habitation of common cranes, they do not experience a shortage of nesting habitats and occupies only the most optimal ones. Wetland ecosystems are unevenly distributed throughout the territory, therefore, distribution of cranes is also uneven: they often form large breeding groups, separated from each other by low-productive habitats supporting only some separate pairs of species. On average, the density of the common cranes population is approximately 1.0-1.5 pairs/km2; in the relatively unfavorable for habitat northern part of the region - 0.3-0.5 pairs/km2; in the favorable western part of the region - 1.8-2.0 pairs/km2. The maximum density in some optimal habitats can reach 4.0-6.0 pairs/km2. Based on an approximate expert assessment of the area of nesting habits of this species and their average density, we have counted 9500-12000 nesting birds on the territory of Eastern Siberia (Irkutsk Oblast, the Republic of Buryatia and Zabaikalsky Krai). A typical clutch usually contains 2 eggs, on average 1.2-1.59 cranes begin flying. The diet is very diverse, it includes mainly vegetable food and, to a lesser extent, animal food. In spring, the cranes frequently eat flowers and buds of Eastern pasqueflower (Pulsatilla patens), as well as the needles of Larix sibirica. The distribution of the species is very variable. Long-term arid and wet climatic periods cause shifts in population ranges. In addition, since the mid-1990s there was also a general increase in its population size in Eastern Siberia.