Key to the success of any bird management programme is that that the public should be advised to stop feeding the pigeons. Where this is not possible, or where this approach has failed, then an alternative strategy can now be adopted.
• From Side Effect to Positive Treatment
• The Italian Experience
• Keep Counting Pigeons
• No safety concerns
• Management solutions now available
Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected faeces or ingestion of infected tissue. There are a number of species of coccidiosis and their effects vary from harmless right through to life threatening. It is treatable, one approach uses a feed additive containing nicarbazin.
Nicarbazin is a complex of two compounds (4,4′-dinitrocarbanilide (DNC) and 4,6-dimethyl-2-pyrimidinol (HDP)) that has been used as a coccidiostat in broiler chicken feeds since the 1950s. It is still used today as a feed additive, for the prevention rather than the treatment of disease.
It is even used in chicken destined for human consumption. At recommended doses however, treatment with Nicarbazin can affect egg laying hens, interrupting egg laying and reducing hatchability.
Nicarbazin was the first agent with broad‐spectrum activity against Eimeria spp. of chickens and is used as a single agent or in combination with antibiotics for prevention and control of coccidiosis in broiler chickens.
When given to egg laying birds, a side effect occurs reducing hatchability and interrupting egg laying. The effect is temporary and birds recover fully 4–6 days after being taken off treated food.
The exact mode of action of nicarbazin is unknown. It compromises the integrity of the egg’s vitelline membrane, allowing yolk and albumen to mix. It is thought that nicarbazin interferes with cholesterol metabolism in the formation of the membrane.
It was the side effect of nicarbazin which Italian veterinarians and researchers explored to help reduce problem pigeon populations. The effect was first verified in studies using racing pigeons and trials for urban pigeons quickly followed. The tests used treated maize in several Italian towns and cities (such as Udine, Carpi, Parma and Forlì) with a total of 552 colonies (85,562 pigeons).
The resulting infertility led to a significant reduction in a short time of the number of pigeons. All sites showed a reduction in the pigeon population of approximately of 48% in 8 months, following a daily administration. Genoa was used as a site for a long period of treatment over 8 years (2005-2012). Here too, a reduction was observed over the first 4 years (35% to 45%) and a further decrease (65% to 70%) over the subsequent 4 years.
The Ghirlandina Tower behind the Duomo in Modena. Peregrine Falcons have lived in the tower during an extensive restoration process and a simultaneous pigeon management programme over many years using nicarbazin treated maize.
To manage pigeons in Bologna, the streets, parks, gardens and piazzas have seen regular manual applications with treated maize every morning, before cafes open and people arrive for work, with automatic dispensers located on roof tops.
Several industrial sites in Italy now use automatic dispensers to deliver treated maize as a means to keep pigeons numbers at an acceptable level and avoid conflict with equipment on site.
1. Counting Pigeons. In all studies, to be effective, it was important to first estimate the population and colonies within a given area, to determine the number of feeding points, to decide whether to use manual or automatic application and the daily dose to be delivered.
2. Start feeding. Pigeons can quickly become habituated to being fed but before any treatment, plain maize kernels are used for a minimum of two weeks, to confirm that the correct locations have been chosen and that the pigeons will eat.
3. Switch to treated maize. Regular corn is then replaced with a nicarbazin treatment. This can be made manually or by automatic feeder. Feeding is usually made at the same time, first thing in the morning.
4. Controlled Application. Whether feeding manually or by feeder, it is possible to deliver only sufficient maize for the number of pigeons visiting each location.
5. Adjusting the dose. As populations decrease, less product is required, but the remaining population needs to be continuously fed for the treatment to be effective.
6. Towards the end of treatment, a new census is conducted and compared with the initial count. The results can then be analysed to determine the overall effect and help in planning the following seasons programme.
Nicarbazin has a good safety and environmental profile. In addition to the low toxicity, the risk to non-target birds is initially determined by the large size of kernels. In addition, the careful distribution of treated feed, to only those birds present at the time of application, provides a control point in any treatment.
There is no risk to raptors that eat pigeons that have consumed treated maize. When pigeons ingest nicarbazin, they metabolize it rapidly and it breaks down into the two components. When a raptor eats a pigeon treated with nicarbazin, the nicarbazin exists in a dissociated form and is consequently inactive because it cannot be absorbed or the remaining inactive nicarbazin, that could be consumed, is irrelevant due to the scarce amount that remains.
Regarding granivorous species, the size of the maize kernels stops them being ingested by birds of smaller sizes than a pigeon. There is similarly no harm to the health of the pigeons. Clinical tests on pigeons treated with nicarbazin have not shown any adverse side effects nor anatomical or functional modifications with regards to their tissue or organs.
The Ghirlanindina Tower behind the Duomo in Modena. Peregrine Falcons have lived in the tower during an extensive restoration process and the pigeon control treatment over many years with nicarbazin treated maize.
A commercial product is available in Italy to manage problem pigeon populations. This uses high quality natural whole maize grains containing 0.08% (800 ppm) nicarbazin.
At recommended rates of 8-10 g of maize grains, per pigeon per day, for a minimum of 5 days a week, applied from March to October, in the first year of treatment, there is a reduction of approximately 20-30%. Provided the programme is implemented correctly, this reduction continues each year, so that after 4-5 years, approximately 20% of the initial population remains.
