Migration strategy of young robin Erithacus rubecula in the east of the Russian plain

In 2015-2019, in the Sysola River valley, we estimated the parameters of the migration stopover of young robins in the taiga in the east of the Russian Plain. A total of 188 birds were captured using mist nets and analyzed. It was established that migratory young robins can be divided into two groups. The first group is transit individuals that leave the stopover without delay on the day of arrival. The other group includes individuals that make stopovers for a long time, on average 3.04 ± 0.57 days. For birds of both groups, a change in body weight and the rate of fat accumulation during the day and throughout the entire migration stopover were revealed. Birds from the first group have insignificant fat reserves that allow them to make migration flights lasting an average of 5.30 ± 0.20 hours. The robins from the second group, during the stopover period, only slightly increase their fat reserves at a rate of 0.33 g per day and by the time of departure are able to make non-stop flights with an average duration of 5.80 ± 0.74 hours. Individuals that decide to stop find themselves in optimal conditions in which they retain their energy reserves and with longer stopover can increase them and make longer migratory flights. As a result, during the autumn migration period over a significant part of the European range of distribution of the studied species, a unified strategy for the behavior of robins at migration stopovers was noted.