From pardal to etxe-txolarrea: An integrative review of the house sparrow Passer domesticus knowledge in the Iberian Peninsula

Abstract

House sparrows, native to the Middle and Near East, have expanded –naturally or with human assistance– to nearly every continent except Antarctica. As a highly anthropodependent species, they have been extensively studied, with over 7,000 research articles published worldwide. In the Iberian Peninsula, house sparrows have long been a familiar presence in cities and farmlands. However, there is a lack of integrative research that synthesizes the existing scientific knowledge on this species. Our review focuses on existing literature to identify spatio-temporal patterns, highlight knowledge gaps, and guide future directions on the research focused on the species. By the use of bibliometric and systematic search approaches, we analyzed 114 peer-reviewed articles conducted in the Iberian Peninsula and focused on house sparrows. Research in this region on this species began in the mid 1980s. Studies have focused mostly on its health (e.g., parasitism, infection rates, physiology), biology (e.g., reproduction, morphology, hybridization, adaptability), behavior (e.g., boldness, social signaling, dominance, infanticide, intraspecific brood parasitism, egg rejection), and ecology (e.g., population trends, habitat selection, abundance, density). Most studies, led by long-standing research groups, have been concentrated in Spain: Madrid, Barcelona, Seville, Huelva, and Badajoz, dominating the research of these topics, while only 5 studies were indentified for Portugal. Besides the geographic bias, we identified critical knowledge gaps, particularly regarding the species’ conservation. Future research may benefit from prioritizing large-scale population studies, distinguish urban and non-urban trends, enhance knowledge of other native sparrows for comparative analyses, and foster collaboration to develop standardized census methods to gain a comprehensive picture of the species' status.