Pigeon contraception instead of culling
How new studies expose the hunting lobby’s “there-is-no-alternative” mantra.
In many cities, pigeons continue to serve as a projection screen for everything that bothers people about urban wildlife.
And as so often when animals are in the way, authorities reflexively resort to the methods of hunting: trapping, poisoning, shooting. What is justified in the open countryside with deer, foxes or wild boar repeats itself in urban spaces with pigeons on a smaller scale.
At the same time, remarkably precise data are now on the table showing that things can be done very differently. Belgium, Spain and Italy have quietly built an alternative model over the years: birth control with nicarbazine pellets instead of bloodstains on the pavement.
Belgium: 40 percent fewer pigeons – and then the authorities turn off the tap
In the Brussels municipality of Ixelles, automatic feeders dispensing contraceptive pellets were installed from 2021 onwards. The goal: to reduce the pigeon population without killing animals. After three years, the number of pigeons had fallen by around 40 percent.
The municipality itself acknowledges “positive effects” from the programme, yet ended it in 2025, officially citing cost reasons. Animal welfare organisations on the ground report a marked increase in pigeon numbers just months after the halt, as the gains previously achieved are being squandered.
While Ixelles withdraws, the city of Brussels is expanding its contraceptive dispensers and publicly promoting the project as a humane alternative: at designated locations, pigeons receive a defined daily quantity of maize kernels treated with nicarbazine to limit reproduction, rather than periodically killing the animals.
Even more striking is the case of Zaventem, a municipality near Brussels. A contraception programme for urban pigeons was launched there in April 2024. After just seven months, the municipality reported a population decrease of 10 percent and described it as a “deliberately humane and animal-friendly solution.”
These figures are highly inconvenient for the hunting logic. They demonstrate:
- Shotgun cartridges are not needed to measurably reduce pigeon populations.
- Continuity is decisive, not violence.
- Short-term political decisions can undo functioning animal welfare projects within a matter of months.
Eight years of data from Catalonia: fewer pigeons, halved costs
Perhaps the most important new study comes from Catalonia. A 2024 study evaluated up to eight years of Nicarbazin bait use across 24 cities and municipalities.
The key findings:
- On average, the pigeon population declined by around 12 percent per year.
- In 68 percent of municipalities, total annual costs halved after three years, because fewer pigeons also means less bait and less effort.
- Non-target species were rarely observed feeding and in such small quantities that no relevant impact on reproduction was detected.
The authors conclude that Nicarbazin is an “effective and selective method in the spirit of animal welfare” for reducing pigeon populations — without trapping, without killing, and without the usual side effects of the hunting-based “problem solution.”
This brings the circle to a close: earlier studies from Genoa (eight years of Ovistop use) and Barcelona (three years of a contraception programme in conflict-prone pigeon colonies) had already demonstrated clear population declines and improved public acceptance when reproduction is limited rather than killing carried out.
Is Ovistop dangerous for pigeons?
Critics are fond of describing Ovistop as “poisoning” pigeons. A look at the specialist literature leaves little substance to this characterisation. Ovistop contains Nicarbazin at a dosage specifically targeting the reproductive system: the agent temporarily disrupts the formation of a stable eggshell, thereby reducing the hatch rate. It does not kill the animals; it renders them temporarily infertile.
Crucially:
- The effect only occurs if pigeons consume the intended quantity on several consecutive days. Individual grains are practically ineffective.
- Once the treatment is discontinued, reproduction returns to normal — the effects are therefore reversible.
- The large-scale evaluations from Spain and Italy reported no systematic health damage to the animals: the pigeons are not “treated as sick,” but simply reproduce less successfully.
Toxicological assessments also classify nicarbazin as practically non-toxic to birds and mammals; the relevant effects occur at the level of reproduction, not as classical poisoning with organ damage or fatalities.
Anyone who describes Ovistop as “dangerous” to pigeons is deliberately conflating two levels: yes, the product interferes with reproduction — that is precisely its purpose. But it does so without the severe suffering caused by trapping operations, neck-breaking, or shotgun fire. From an animal welfare perspective, it is difficult to justify why deliberately preventing the hatching of chicks should be considered more cruel than the routine killing of adult animals.
The Barcelona Controversy: How to Miscalculate a Method
Opponents of the method also like to cite a 2020 study from Barcelona that concluded nicarbazin had “no effect” on the pigeon population. This paper continues to be cited in hunting-adjacent circles to this day, in order to portray birth control as naive or ineffective.
What is almost always omitted from the public debate:
- The study essentially examined only one year of treatment. Population biology, however, operates across multiple reproductive cycles.
- At the same time, pigeon density in the control areas increased by approximately 10 percent, while it stagnated in the treatment area.
- More recent and considerably more comprehensive studies from Barcelona and across Catalonia do in fact demonstrate clear population declines over several years when the system is implemented consistently.
The supposed “refutation” of the contraceptive method thus proves to be a classic pseudo-debate of the kind familiar from hunting advocacy: an unfavourably designed study or one conducted over too short a period is seized upon to discredit an unwelcome alternative that does not fit the worldview of necessary culling.
Safety: Minimal Risk to Other Species and Birds of Prey
A frequently raised objection holds that nicarbazin could endanger other bird species or even birds of prey that feed on pigeons. Here too, the evidence base has grown more robust.
A 2023 review on the safety of nicarbazine in birds of prey concludes that secondary exposure through the consumption of treated pigeons poses neither acute nor chronic risks. Nicarbazine is classified as 'practically non-toxic' to birds and mammals; the only conceivable effect in non-target birds would be a temporary reduction in egg hatch rates under conditions of sustained high intake.
Furthermore, nicarbazine breaks down rapidly in the body into two compounds that individually no longer have any contraceptive effect. Experts therefore consider it highly unlikely that birds of prey occasionally consuming a treated pigeon would receive a relevant dose.
Practical experience with several hundred pigeon colonies across Europe now tells the same story:
- no documented cases of poisoning in birds of prey,
- no significant side effects in mammals,
- The effect on pigeons is fully reversible once the bait is discontinued.
To speak of 'poison', as is done in certain pro-hunting campaigns, is simply scientifically incorrect.
Hunting logic under stress test: What happens when the shooting stops
Perhaps the most important question from an animal welfare perspective is: what does all of this reveal about the fundamental assumptions of hobby hunters, which are so readily adopted even in urban contexts?
The classic hunting narrative goes like this:
- There are too many animals.
- The only effective solution is culling.
- All other methods are, at best, a supplement and, at worst, ideology.
Pigeon birth control demonstrates precisely the opposite in practice:
- Populations can be reduced in a measurable and predictable manner without killing a single animal.
- Animals suffer less because they are never born in the first place, rather than perishing after being mutilated by shotgun fire.
- Costs decrease in the medium term, rather than spiralling out of control in an endless cycle of trapping and killing operations.
What the pigeon demonstrates in the urban environment is directly transferable to other wildlife issues: where there is political will, alternatives to culling suddenly become possible — whether through birth control, habitat management, or the consistent adaptation of human behaviour.
The true constant is not 'too much wildlife', but a system that profits from culling and invests it with ideological significance.
What cities in Switzerland and the German-speaking world could learn from this
While Brussels, Zaventem, Barcelona, and Genoa work with concrete figures, many Swiss and German municipalities still rely on buzzwords. Talk of “exploding pigeon populations,” “hygiene weapons,” and “rats of the skies” abounds. Shooting squads and pest control companies are only too happy to supply the appropriate services.
International experience with Nicarbazin feed suggests a different strategy:
- Count first, rather than making claims. Reliable population assessments are the foundation of any measure.
- Then address the root cause: regulate human feeding behavior, improve waste management, neutralize nesting sites, and use birth control as a supplementary measure.
- Ensure transparency: the public has a right to know whether their municipality is having animals systematically killed, even though demonstrably more animal-friendly alternatives exist.
The example of Ixelles shows that the method can fail politically: success is no guarantee of continuation when short-term budget debates or ideological reservations are given more weight than animal welfare and long-term effectiveness.
That is precisely why a critical public is needed — one that asks hard questions when authorities reflexively reach for the gun, or when hunting-affiliated circles use supposedly “scientific” counter-arguments to stir sentiment against non-lethal methods.
The new data from Belgium, Catalonia, and Italy confirm what animal welfare advocates have been demanding for years: we do not need to kill animals to resolve conflicts. We must be willing to change the way we treat them.
Pigeon contraception is not a romantic urban ecology project, but a soberly calculated alternative to the logic of hunting. It reduces populations, saves money, spares animals, and steadily erodes the narrative of supposedly unavoidable culling.
The question, therefore, is not whether such methods work. The question is how much longer politicians and the hunting lobby will continue trying to ignore them.
