Birds and other animals are frequently killed by cars,causing the death of many million individuals per year.Why some species are killed more often than others has never been investigated.In this work hypothesized tha...Birds and other animals are frequently killed by cars,causing the death of many million individuals per year.Why some species are killed more often than others has never been investigated.In this work hypothesized that risk taking behavior may affect the probability of certain kinds of individuals being killed disproportionately often.Furthermore,behavior of individuals on roads,abundance,habitat preferences,breeding sociality,and health status may all potentially affect the risk of being killed on roads.We used information on the abundance of road kills and the abundance in the surrounding environment of 50 species of birds obtained during regular censuses in 2001 2006 in a rural site in Denmark to test these predictions.The frequency of road kills increased linearly with abundance,while the proportion of individuals sitting on the road or flying low across the road only explained little additional variation in frequency of road casualties.After having accounted for abundance,we found that species with a short flight distance and hence taking greater risks when approached by a potential cause of danger were killed disproportionately often.In addition,solitary species,species with a high prevalence of Plasmodium infection,and species with a large bursa of Fabricius for their body size had a high susceptibility to being killed by cars.These findings suggest that a range of different factors indicative of risk-taking behavior,visual acuity and health status cause certain bird species to be susceptible to casualties due to cars.展开更多
Generalist mammalian predators hunt for prey in different ways than raptors,often relying on ambush attack.Such differences in predator behavior can have profound effects on susceptibility of different species of prey...Generalist mammalian predators hunt for prey in different ways than raptors,often relying on ambush attack.Such differences in predator behavior can have profound effects on susceptibility of different species of prey to predation,but can also modify the behavior of prey.We investigated susceptibility of common birds to predation by domestic cats Felis catus,relying on an extensive data set on prey abundance and prey availability as determined by standardized bird counts.Susceptibility to cat predation for different species of birds was not significantly correlated with susceptibility to predation by sparrowhawk Accipiter nisus,but with susceptibility to goshawk Accipiter gentilis predation. Susceptibility to goshawk predation was independently predicted by susceptibility to cat and sparrowhawk predation.We cross-validated our estimate of susceptibilityto cat predation by showing that the frequency of birds with tail loss increased strongly with sus-ceptibility to cat predation.Male birds were disproportionately preyed upon,especially if havingsong posts low in the vegetation,and if having short flight distances when singing.Colonially breeding species were less susceptible to predation than solitary species.Bird species with high levels of innate immune defense against bacterial infections had high susceptibility to cat predation.These findings suggest that predation by cats has been an important selection pressure affecting anti-predation behavior,sexual display and immune function in common birds.展开更多
Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may prov...Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.展开更多
文摘Birds and other animals are frequently killed by cars,causing the death of many million individuals per year.Why some species are killed more often than others has never been investigated.In this work hypothesized that risk taking behavior may affect the probability of certain kinds of individuals being killed disproportionately often.Furthermore,behavior of individuals on roads,abundance,habitat preferences,breeding sociality,and health status may all potentially affect the risk of being killed on roads.We used information on the abundance of road kills and the abundance in the surrounding environment of 50 species of birds obtained during regular censuses in 2001 2006 in a rural site in Denmark to test these predictions.The frequency of road kills increased linearly with abundance,while the proportion of individuals sitting on the road or flying low across the road only explained little additional variation in frequency of road casualties.After having accounted for abundance,we found that species with a short flight distance and hence taking greater risks when approached by a potential cause of danger were killed disproportionately often.In addition,solitary species,species with a high prevalence of Plasmodium infection,and species with a large bursa of Fabricius for their body size had a high susceptibility to being killed by cars.These findings suggest that a range of different factors indicative of risk-taking behavior,visual acuity and health status cause certain bird species to be susceptible to casualties due to cars.
文摘Generalist mammalian predators hunt for prey in different ways than raptors,often relying on ambush attack.Such differences in predator behavior can have profound effects on susceptibility of different species of prey to predation,but can also modify the behavior of prey.We investigated susceptibility of common birds to predation by domestic cats Felis catus,relying on an extensive data set on prey abundance and prey availability as determined by standardized bird counts.Susceptibility to cat predation for different species of birds was not significantly correlated with susceptibility to predation by sparrowhawk Accipiter nisus,but with susceptibility to goshawk Accipiter gentilis predation. Susceptibility to goshawk predation was independently predicted by susceptibility to cat and sparrowhawk predation.We cross-validated our estimate of susceptibilityto cat predation by showing that the frequency of birds with tail loss increased strongly with sus-ceptibility to cat predation.Male birds were disproportionately preyed upon,especially if havingsong posts low in the vegetation,and if having short flight distances when singing.Colonially breeding species were less susceptible to predation than solitary species.Bird species with high levels of innate immune defense against bacterial infections had high susceptibility to cat predation.These findings suggest that predation by cats has been an important selection pressure affecting anti-predation behavior,sexual display and immune function in common birds.
文摘Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.
