Ornis Hungarica. vol.10. (2000) p.123-127.
Fall migration of the Isabelline Shrike (Lanius isabellinus) in West Mongolia
Our study was carried out during 1 August - 4 October 1996 at Khovd, Western Mongolia. We banded 86 Isabelline shrikes (Lanius isabellinus) and recaptured 12 of them. Each bird was aged and weighed. We estimated the amount of the stored fat on a scale of 0 to 8. We separated 2 age groups as juveniles and adults. The adult Isabelline Shrikes began their autumn migration exactly at the same time as juveniles (6 August). There was a definite difference in the migratory speed of the two groups. Ten juveniles and 1 adult were recaptured. Juvenile birds spent less than 1 day in the area, while the adults seemed to have an even shorter stopover. The arrival period of birds consisted of 7 pentads. There was no significant difference in the amount of fat and body mass between the pentads in case of young birds. The adult birds got fatter and heavier with time. The adult birds were also heavier than the young ones. Based on these results, we propose that the migratory strategy of Isabelline shrike is similar to that of its close relative, the Red-backed Shrike (Lanius collurio).