Age structure and movement of Capercaillie (Tetrao urogallus) males in NW Russia - A two-compartment model

Abstract

Capercaillie (Tetrao urogallus) males in the remnant unlogged forest of NW Russia have an unusual age structure, with more older than younger birds. In logged forest, the more normal opposite occurs. A possible explanation involves two-way movement in which youngsters disperse from unlogged to logged forest and older birds, up to their third spring, do the reverse. As Capercaillie cocks do not generally attain mating status until their third spring or later, both movements could be classed as natal dispersal. We develop a two-compartment population model that shows how this could happen and make a first approximation of the numbers and distances that would be involved. The model highlights gaps in knowledge that should be addressed by further fieldwork.