Territory strategy of the migratory Brown Shrike Lanius cristatus

Brown Shrikes Lrrinus cristntus are both transients and winter residents in Taiwan. Large numbers of birds crowd into the available habitat during the transient period, and the cost of maintaining territories changes greatly. depending on the number of shrikes pres-ent. This study examined how wintering Brown Shrikes adapt to the changing level of competition in territory establishment. About 24%) of autumn transients arrived before any wintering birds, while 73 % of wintering birds arrived during autumn transient time. The frequency of aggression recorded was significantly related to the number of birds seen along the transect line that day Among ringed birds that returned during transient time, 80 % returned directly to their previous territories, but some waited for the departure of transient birds before establishing territories. Territory compression occurred at high pop-ulation densities. Departure from and arrival at the study area were frequent during the winter. but no birds moved territories within the study area. On average, 25 % of ringed wintering shrikes returned to the study site in the subsequent years. while n o transients I returned. This low site tenacity may be. in the migration route. part, a result of a high persecution rate along The intensity of competition and the economics of resource defence determine the expression of territoriality for a given species in its habitat. Researchers have examined many as-pects of territoriality. including agressive advantages over newcomers (Krebs 1982. Waage 1988). the costs and ben