Philopatry and habitat selection were examined for migratory populations of the two sympatric shrike species, the Bull-headed (Lanius bucephalus) and Brown (L. cristatus) shrikes in northern Japan between 1992 and 1997. Although 18% of banded Bull-headed Shrike males returned to the previous breeding area, no female did. In Brown Shrikes, 43% and 13% of banded males and females, respectively, returned to the area. Brown Shrikes are significantly more philopatric than Bull-headed Shrikes. Even successful breeders in Bull-headed Shrikes did not always return to the area near their nesting site of the previous year. Successful breeders in Brown Shrikes were faithful to their past breeding site. Brown Shrikes decreased by 67% due to habitat loss over four years, while the population of Bull-headed Shrikes was stable. The degree of philopatry was inconsistent with the population trends of the two shrikes. While Bull-headed Shrikes did not have habitat preferences in the study area, Brown Shrikes bred mainly in natural grasslands with shrubs. Since available habitat for Brown Shrikes has decreased rapidly in and near the study area, the philopatry of Brown Shrikes may result from a scarcity of habitat that inhibits dispersal. Bull-headed Shrikes may have a higher tendency to disperse because they are habitat generalists. With its more narrow requirements, the Brown Shrike appears to have suffered significantly from habitat loss, while the Bull-headed Shrike has not been adversely affected.
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Vol. 74 • No. 1