Evaluation of 8 years of fertility control (nicarbazin) to manage urban pigeon populations

Context: The common pigeon (Columba livia var. domestica) is a synurbic species widely distributed around the world. High local densities of pigeons have negative impacts on animal and public health. Urban pigeon fouling also damages buildings and infrastructures, resulting in increased maintenance costs. Although the reduction of food and shelter would be the most effective control method, it does not apply in most cases where the amount of shelter and food can be unlimited and control very difficult achieve. However, a reduction and control of the population by fertility control using nicarbazin (NCZ, Ovistop®) could be achieved without the need to capture and remove any specimens.

Aim and methods: The aims of this study were (1) to describe the experience of up to 8 years of use of fertility control by NCZ on pigeon numbers in 24 towns and cities in Catalonia (Spain), (2) to assess the potential for non-target species to be affected by NCZ, and (3) to quantify the costs of implementing local population control of urban pigeons via NCZ. Local number of pigeons was estimated via population censuses.

Key results: From the beginning of the treatment, a significant steady decreasing trend (average of −12% per year) in the pigeon abundance was registered. In very few instances, non-target birds species were observed to feed on NCZ.

Conclusions and implications: NZC was an effective and selective method of animal welfare to reduce the total number of pigeons in the municipalities included in this study, while not affecting other non-target species. The estimated cost of the annual treatment was €33.6 per pigeon; in 68% of the municipalities, the total annual cost was halved after 3 years of treatment. The findings of this study are in agreement with previous experiences controlling pigeon colonies by using NCZ in other countries.