Human landscape transformation, especially urbanization, strongly affects ecosystems worldwide. Both urban stressors and parasites have negative effects on organism health, however the potential synergy between those factors has been poorly investigated. We analysed the body condition (i.e. body mass after controlling for wing chord) of 2043 house sparrows (adults and yearlings) captured in 45 localities along an urbanization gradient in relation to Plasmodium, Haemoproteus and Leucocytozoon infection status. Body condition was negatively related to urbanization level and to urbanized land coverage but only in yearling birds from urban habitats. In addition, bird body condition tended to increase in rural habitats, significantly in the case of yearlings. Infected individuals by Plasmodium or Haemoproteus had higher body condition than un-infected birds, but this pattern could be due to a selective disappearance of infected individuals with lower body condition as suggested by the reduced variance in body condition in infected birds in urban habitats. These results provide support for a negative impact of urbanization on bird body condition, while Plasmodium and Haemoproteus may exert selection against individuals with lower body condition living in urban habitats, especially during earlier life stages, underlining the synergistic effects that urbanization and parasites may have on wild birds.

人类景观的转变，尤其是城市化，极大地影响着全世界的生态系统。城市压力源和寄生虫均对生物体健康产生负面影响，但是这些因素之间的潜在协同作用尚未得到充分研究。我们分析了在45个地区捕获的2043只麻雀（成年和一岁）的体况（即控制翼弦后的体重），沿城市化梯度与疟原虫，血红蛋白和白细胞增生症相关感染状态。身体状况与城市化水平和城市化土地覆盖率呈负相关，但仅与来自城市栖息地的一岁鸟有关。此外，在一岁的情况下，农村地区的鸟类身体状况趋于增加。疟原虫或变形杆菌感染的个体比未感染的鸟类具有更高的身体状况，但是这种模式可能是由于身体状况方差减少表明城市生活环境中的身体状况差异减小，提示身体状况较低的受感染个体选择性消失。这些结果为城市化对鸟类身体状况的负面影响提供了支持，而疟原虫和血红蛋白 可能会针对居住在城市栖息地（尤其是生命早期阶段）的身体状况较低的个体做出选择，从而突显了城市化和寄生虫对野生鸟类可能产生的协同效应。