A mathematical model of autumn migration of five raptor species in the «bottleneck» at the south of Lake Baikal was constructed. The model includes the next parameters: numbers and spatial distribution of birds in main zones in dependence from the bird density at the moment of migration beginning flight speed before coming into the migratory corridor and inside it cloud situation at the territory birds are collected into the corridor from, and affecting of cloud cover to speed of the birds time distribution of birds starting their migration inside its general time according a bi-normal distribution interspecific differences in migratory behavior with different types of cloud cover, and in dependence of energetic migratory status of birds. The model supports a leading role of the cloud cover, and shows a need to input additional factors, e.g. atmospheric precipitation, temperature, and wind. For species preferring to soar, the model shows higher flight speed during coming to the migratory corridor than initially presumed, and, controversially, it shows lower speed for the «flapping flight» species but Goshawk. Lower kurtosis in the modeling charts in comparison to factual migratory peaks let to presume birds, which are not yet wholly ready to migrate, are partially involved with birds being energetically ready for into the migration.