Field Evidence of Erythrism and Partial Leucism in House Sparrow (Passer domesticus) Populations of Ajmer City, Rajasthan, India

Abstract

Background: The House Sparrow (Passer domesticus) is a widely distributed and well-studied urban passerine, adapted to a range of environments from rural farmlands to densely populated cities across the globe. Aims: The present study document and analyse the occurrence of plumage aberrations in House Sparrows (Passer domesticus) in Ajmer City, Rajasthan, and to assess the possibility of a localized, potentially genetically distinct population maintaining these rare traits. Study Design:  Observational, field-based study focusing on phenotypic variation within a free-living urban bird population. Place and Duration of Study: Urban and suburban areas of Ajmer City, Rajasthan, India, from January 2024 to April 2025. Methodology: Systematic field surveys were conducted across multiple sites within the Ajmer district using direct visual observation, supported by photography for documentation. Individual sparrows displaying atypical plumage were identified and compared against the standard plumage characteristics of Passer domesticus. Morphological parameters such as plumage coloration, body size, and apparent health status were recorded. Results: A total of three erythristic House Sparrows (one male and two females) were documented from three distinct locations within Ajmer City. These individuals consistently displayed reddish-brown pigmentation on the crown, nape, back, and ventral regions, distinctly different from standard plumage. In addition, a single case of partial leucism was recorded, characterized by localized patches of depigmented (whitish) feathers. Conclusion: The repeated sightings of erythristic and leucistic House Sparrows in Ajmer suggest the potential existence of a localized, genetically influenced anomaly within the population. Further genetic and ecological studies are necessary to confirm inheritance patterns and to explore the adaptive significance of these rare plumage traits in an urban environment.