Nicarbazin has no effect on reducing feral pigeon populations in Barcelona.
BACKGROUND: Nicarbazin is an anti-coccidial product sometimes used as a contraceptive to reduce the size of feral pigeon populations. However, its effectiveness in reducing pigeon population size in cities has caused some controversy. Here, we eval- uate its effectiveness in the city of Barcelona. RESULTS: In 2017, the Barcelona City Council set 23 feeding stations with nicarbazin and ten with placebo (untreated corn). Cen- suses were undertaken before and after one year of treatment, within a 200-m radius around each feeder. We also censused 28 circles of 200 m radius distributed randomly 200 m from the feeders and 28 circles > 500 m from the feeders, which acted as controls. Population size across the whole city was also evaluated pre- and post treatment. We found that feral pigeon den- sity did not change after one year of treatment, either in the circles around feeding stations with nicarbazin or in the areas around control stations at 200 and > 500 m from the feeders. Population size in placebo circles rose after a year by 10%. A pigeon census for the whole of Barcelona showed a 10% increase. CONCLUSION: Overall, our results indicate that the nicarbazin treatment had no effect on feral pigeon population size, and we advise against its use as a pigeon control method, at least in large cities.