St Barnabas_07_08_2ages 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影响动物种群，如今学界愈发认可传染病会对生物多样性产生负面影响。家麻雀（*Passer domesticus*）种群在欧洲诸多城镇均出现下降，但其种群衰退的具体原因仍不明晰。本研究针对1995年以来家麻雀种群数量已下降71%的伦敦郊区展开调查，旨在探究寄生虫感染与家麻雀种群统计学特征之间的关联。研究发现，伦敦郊区家麻雀的莱氏疟原虫（*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，均与莱氏疟原虫感染强度呈负相关关系。其他寄生虫的感染率则低得多，且与家麻雀存活率无显著关联，对种群增长率也未表现出负面影响。混合感染率较低，这表明家麻雀并未出现免疫功能受损的情况。本研究结果表明，莱氏疟原虫（*P. relictum*）感染或正影响着郊区家麻雀的种群动态。伦敦地区家麻雀对莱氏疟原虫感染的种群统计学敏感性，或反映出该区域近期接触该寄生虫的概率有所上升。