Nicarbazin-Based Fertility Control for Urban Pigeon Management: A Review of Experimental, Regulatory and Operational Evidence.

High urban pigeon densities can generate conflicts related to building and heritage damage, public-health concerns, nuisance, and the need for socially acceptable population-management strategies. The management of feral pigeon (Columba livia) populations in urban environments requires approaches that are effective, sustainable, publicly acceptable, and legally compliant. Among available non-lethal options, fertility control based on nicarbazin, originally developed in the 1950s as a poultry anticoccidial before being adapted for urban bird management, has become one of the most extensively investigated strategies. This narrative review synthesizes the scientific literature and regulatory experience concerning nicarbazin-based fertility control, including products authorized as veterinary medicinal products in Europe (Ovistop®, ACME DRUGS Srl, Cavriago, Italy and R12®, ACME Srl, Cavriago, Italy) and as an EPA-registered pesticide product in the United States (OvoControl® P, Innolytics, LLC, CA, USA), covering its historical development, mechanism of action, regulatory frameworks, experimental evidence, long-term field studies, and post-marketing experience. The available evidence indicates that the effectiveness of nicarbazin is supported by multiple independent sources, including laboratory investigations, pharmacokinetic studies, long-term field evaluations, regulatory assessments, and more than two decades of operational use, although successful population management depends not only on biological efficacy but also on program implementation, monitoring, and long-term management. Based on the evidence reviewed, a Three-Pillar Framework integrating population monitoring, fertility control, and environmental and social management is proposed. Remaining evidence gaps concern the standardization of monitoring and outcome assessment, the influence of population connectivity, and the economic evaluation of long-term programs, identifying priorities for future research. Overall, nicarbazin-based fertility control emerges as a scientifically validated, reversible, and humane tool for the long-term management of urban pigeon populations within a structured, adaptive framework.