house sparrow parasites from Avian malaria-mediated population decline of a widespread iconic bird species.

Parasites have the capacity to affect animal populations by modifying host survival, and it is increasingly recognized that infectious disease can negatively impact biodiversity. Populations of the house sparrow (<i>Passer domesticus</i>) have declined in many European towns and cities, but the causes of these declines remain unclear. We investigated associations between parasite infection and house sparrow demography across suburban London where sparrow abundance has declined by 71% since 1995. <i>Plasmodium relictum</i> infection was found at higher prevalences (averaging 74%) in suburban London house sparrows than previously recorded in any wild bird population in Northern Europe. Survival rates of juvenile and adult sparrows and population growth rate were negatively related to <i>Plasmodium relictum</i> infection intensity. Other parasites were much less prevalent and exhibited no relationship with sparrow survival and no negative relationship with population growth. Low rates of co-infection suggested sparrows were not immunocompromised. Our findings indicate that <i>P. relictum</i> infection may be influencing house sparrow population dynamics in suburban areas. The demographic sensitivity of the house sparrow to <i>P. relictum</i> infection in London might reflect a recent increase in exposure to this parasite.

寄生虫可通过改变宿主存活率对动物种群造成影响，学界亦日益认可传染病可对生物多样性造成负面影响。家麻雀（*Passer domesticus*）在欧洲诸多城镇的种群数量均出现下降，但其种群衰退的具体原因仍不明确。本研究针对伦敦郊区展开调查——该区域自1995年以来家麻雀种群数量已下降71%，旨在探究寄生虫感染与家麻雀种群动态之间的关联。研究发现，伦敦郊区家麻雀的禽疟原虫（*Plasmodium relictum*）感染率平均达74%，高于此前北欧地区所有野生鸟类种群的记录水平。幼鸟与成鸟的存活率以及种群增长率，均与禽疟原虫感染强度呈负相关关系。其余寄生虫的感染率则显著更低，且与家麻雀存活率、种群增长率均无关联，亦未表现出对种群增长的负面作用。低混合感染率表明，家麻雀并未出现免疫功能受损的情况。本研究结果显示，禽疟原虫（*P. relictum*）感染或可影响郊区家麻雀的种群动态。伦敦地区家麻雀对该寄生虫感染的种群动态敏感性，或反映出该种群近期接触禽疟原虫的概率有所上升。