Barcelona: Pigeons Receive Contraceptives

An excessive pigeon population can be a problem in many cities, causing suffering to the animals and health issues for the city. 

Many Barcelona residents are fed up with the pigeons. The birds also cause considerable damage to buildings and other structures. “Pigeon droppings are acidic and can corrode stone or metal over time”, according to one expert.

They also cause problems in grain storage facilities (e.g. in the port) and in gardens (they recognise recently planted seeds and feed on them).

Barcelona is estimated to have 1’200 pigeons per square kilometre. An unusual measure is now intended to keep the population under control.

The overpopulation of pigeons leads to a reduction in the quality of life and physical condition of the animals, mainly due to the constant stress of competing for food. Their immune systems are compromised, and this situation can pose a public health problem, as some birds may suffer from diseases or act as carriers of pathogens.

The authorities have long been trying to address this overpopulation through mass culling of pigeons — a method that is increasingly rejected by a citizenry conscious of animal rights. Furthermore, various international studies have demonstrated the lack of effectiveness of this method for controlling pigeon populations, as it triggers an increase in the fertility of the remaining pigeons and causes the situation to return to pre-cull levels within a few months. 

To combat the overpopulation of pigeons while ensuring animal welfare, the Barcelona City Council began in 2016 to design a management strategy that would include a method of fertility control. Corn coated with nicarbazine, a contraceptive that reduces egg production, is used. The experience was pioneering in implementing a city-wide strategy using contraceptive feed to control pigeon abundance in densely populated and therefore conflict-prone colonies.

In addition to providing the contraceptive feed, citizen surveys were conducted over two six-month periods, with the aim of expanding knowledge about the feeding habits of pigeons by the citizens of Barcelona, which is the main factor contributing to overpopulation. The results of the surveys made it possible to design specific awareness campaigns for each group of feeders (from citizens who feed the pigeons sporadically to “large feeders”, who provide up to 15 kg of food daily).

As a result of the implemented management strategy, after five years a decline of 2,278 individuals was recorded (from 3,801 in 2017 to 1,523 in 2021), representing a 60% reduction in the number of pigeons in those colonies treated with nicarbazine.

The method applied has proven effective not only in terms of the goal of reducing the number of pigeons in the nicarbazine-treated flocks, but also with regard to the welfare of the treated animals and non-target species. However, to increase the effectiveness of this method, greater cooperation from citizens is required, and this can be achieved through the awareness campaigns designed to reduce the food offered to pigeons daily in some areas of the city of Barcelona.

The «pill» from the vending machine

Since it proved impossible to dissuade tourists from feeding the pigeons, bird feeders have now been installed throughout Barcelona. The clever part? The grains are laced with the harmless contraceptive and are intended to bring the population back to a «healthy» guide the birds. However, it only makes sense if other cities follow suit, so that the birds don't simply move into other areas. If it works, it will certainly make sense in the long run from an animal welfare perspective as well.

Barcelona already celebrated a success in a field study regarding the ethical management of wild boar populations using a contraceptive vaccine.