摘要
Individuals which have invaded urbanized environments are reported to engage in riskier behav-iors,possibly influenced by the scarcity of predators in urbanized areas.Here,we studied the risk-taking behavior of birds which had invaded a new natural environment,rather than an artificial urban environment,using recently established populations of the bull-headed shrike Lanius bu-cephalus,which naturally colonized three subtropical islands in Japan.We compared flight initi-ation distance(FID),the distance at which an individual approached by a human initiates flight,be-tween the islands and the temperate mainland.FID was longer for the insular shrikes compared with the mainland shrikes after controlling for other factors,indicating that the individuals which had invaded a new natural environment had a lower propensity for risk-taking.A possible explan-ation for these results is that low risk-taking behavior might be adaptive on the islands due to predation by the black rat Rattus rattus,an unfamiliar predator not found in shrike habitats on the temperate mainland.Further studies are needed to examine the nest predation rate,predator species,and nest site selection of these insular shrike populations.
基金
This study was supported by the National Muscum of Nature and Scicnee,Tokyo(Nos 20183001 and 20193001 to S.H.).
