Barn swallows Hirundo rustica have white spots on their tail feathers, and they have been hypothe-sized to be a handicap because white spots are prone to feather breakage, ectoparasites are dispro-portionately common ...Barn swallows Hirundo rustica have white spots on their tail feathers, and they have been hypothe-sized to be a handicap because white spots are prone to feather breakage, ectoparasites are dispro-portionately common in white spots, and size of white spots increases with tail length. Here I testfor attractiveness of narrow and long tail spots by manipulation of their shape while using com-plete painting of spots and an absence of treatment as a control. Female barn swallows are knownto differentially invest in reproduction when mated to attractive males. Spot manipulation tookplace during laying of the first clutch, and there were no effects of treatment on clutch size or broodsize of first or second broods. In contrast, the incidence of second clutches and the total number ofeggs and fledglings produced during the breeding season was larger in males with painting of theside of tail spots rather than painting of the tip of spots, painting of entire spots, or no treatment.These findings are consistent with the hypothesis that it is the shape rather than the size of tailspots that affects differential reproductive effort by female barn swallows.展开更多
The level of genetic variation among individuals may affect performance by reducing the ability of prey to detect and escape from predators if lack of genetic variation reduces flight ability directly or indirectly th...The level of genetic variation among individuals may affect performance by reducing the ability of prey to detect and escape from predators if lack of genetic variation reduces flight ability directly or indirectly through reduced parasite resistance. We investigated vulnerability of common avian prey species to predation by the sparrowhawk Accipiter nisus and the goshawk A. gentilis in relation to an index of genetic similarity among adults of potential prey species. We estimated a prey vulnerability in- dex that reflects the abundance of prey relative to the expected abundance according to local population density, and related this index to band sharing coefficients based on analyses of minisatellites for adults in local breeding populations. The prey vulnera- bility index was positively correlated with the band sharing coefficient in both predators, even when controlling for potentially confounding variables. These findings indicate that prey species with high band sharing coefficients, and hence low levels of genetic variation, are more readily caught by avian predators. Therefore, predation may constitute a major cost of low levels of genetic variation in extant populations of prey [Current Zoology 61（1）： 1-9, 2015].展开更多
文摘Barn swallows Hirundo rustica have white spots on their tail feathers, and they have been hypothe-sized to be a handicap because white spots are prone to feather breakage, ectoparasites are dispro-portionately common in white spots, and size of white spots increases with tail length. Here I testfor attractiveness of narrow and long tail spots by manipulation of their shape while using com-plete painting of spots and an absence of treatment as a control. Female barn swallows are knownto differentially invest in reproduction when mated to attractive males. Spot manipulation tookplace during laying of the first clutch, and there were no effects of treatment on clutch size or broodsize of first or second broods. In contrast, the incidence of second clutches and the total number ofeggs and fledglings produced during the breeding season was larger in males with painting of theside of tail spots rather than painting of the tip of spots, painting of entire spots, or no treatment.These findings are consistent with the hypothesis that it is the shape rather than the size of tailspots that affects differential reproductive effort by female barn swallows.
文摘The level of genetic variation among individuals may affect performance by reducing the ability of prey to detect and escape from predators if lack of genetic variation reduces flight ability directly or indirectly through reduced parasite resistance. We investigated vulnerability of common avian prey species to predation by the sparrowhawk Accipiter nisus and the goshawk A. gentilis in relation to an index of genetic similarity among adults of potential prey species. We estimated a prey vulnerability in- dex that reflects the abundance of prey relative to the expected abundance according to local population density, and related this index to band sharing coefficients based on analyses of minisatellites for adults in local breeding populations. The prey vulnera- bility index was positively correlated with the band sharing coefficient in both predators, even when controlling for potentially confounding variables. These findings indicate that prey species with high band sharing coefficients, and hence low levels of genetic variation, are more readily caught by avian predators. Therefore, predation may constitute a major cost of low levels of genetic variation in extant populations of prey [Current Zoology 61（1）： 1-9, 2015].
