Data on dynamics of the great cormorant (Phalacrocorax carbo) nesting abundance in the Torey lakes (Zabaikalsky krai) in 1990-2021

Steppe Torey Lakes in the Daurian Nature Reserve are one of the most important nesting places of the great cormorants Phalacrocorax carbo (Linnaeus, 1758) in Transbaikalia. Cormorants nest here on the ground of islands. Multiyear climatic cycles have a decisive influence on the dynamics of water level in the Torey Lakes, as well as on the breeding success and population dynamics of cormorants. During the wet climatic period in 1982-1998, the lakes were water-rich and the cormorant number had been increasing; the dry period began in 2000, and in 2020 and 2021 the lakes began filling up again. The significant depletion of the food supply associated with mass mortality of silver Prussian carp (Carassius auratus L., 1758) during the fall of water level in the lakes lead to rise in mortality of small birds from 2003, and by 2007-2008 it reached 90-95%. In spite of rapid decrease of food resources, the number of nesting cormorants continued to increase at the beginning of the dry period and reached 4,212 pairs in 2006. That was connected with migration of birds to the Torey Lakes from the more dry nesting places in Transbaikalia and Mongolia. Cormorant abundance on the Torey Lakes decreased rapidly starting from 2007. Cormorants stopped nesting in 2010 after the islands were connected with the shore in 2008-2009 and colonies were destroyed by fissipedes. During the dry period of 2000-2020, cormorants inhabited almost all relatively large non-dry rivers and lakes in the southern part of Za- baikalsky Krai, but only a small part of birds were able to nest there.