The Pigeon 

What do the great squares of the world—Venice, Milan, Rome, Moscow, Mecca, Delhi, Berlin, New York, Basel, and Stuttgart—have in common? They are all populated by large numbers of feral pigeons. All over the world, regardless of religion or political views, pigeons are fed, cherished, and loved—yet also hated, despised, and persecuted. No other animal divides opinion as sharply as the pigeon. Few creatures have provoked such polarized attitudes and emotions. While white pigeons are seen as symbols of the Holy Spirit, love, and peace, city pigeons are often labeled "rats of the sky" or "flying garbage."

For thousands of years, pigeons have repeatedly settled in cities. But why do pigeons thrive in human environments? The natural habitat of the rock pigeon shares key features with urban landscapes. Bare urban canyons with tall facades resemble rocky coastal cliffs. Pigeons prefer areas with sparse vegetation and nest in dim grottoes and rock crevices—structures also found in cities.

Urban pigeons are content with simple nests made of twigs, branches, string, paper, and similar materials. These nests are built on almost any horizontal surface, such as ledges, bay windows, protrusions, niches, awning boxes, or illuminated signs. The female pigeon lays two eggs per clutch, and depending on the climate and food availability, may have between two and six clutches per year. The mortality rate among young pigeons is estimated at 50%, meaning a pigeon pair raises about three to four fledglings annually. These young pigeons reach sexual maturity at around four months. Pigeons are highly habitual and return to their original nesting sites, even if those sites have since been altered through renovations or new construction. As a result, newly built or renovated structures are quickly reoccupied by pigeons.

Pigeons primarily feed on seeds and bird feed. In urban areas, however, they also consume human food scraps such as French fries and breadcrumbs. This is why areas near food stands, sausage vendors, bakeries, and similar establishments are especially frequented.

City pigeons gather in breeding flocks around their nesting and resting areas. So-called feeding flocks—consisting of members from various breeding groups—require larger territories, depending on the available food supply. If targeted trapping or eradication measures reduce these breeding flocks, pigeons from neighboring districts quickly move in to occupy the vacated spaces.

From both a material and hygienic perspective, city pigeons are considered pests:

Material aspect:
Pigeon droppings are extremely corrosive (containing nitric acid) and damage even the most modern building materials such as concrete, aluminum, sandstone, brick, marble, and even steel. The acid penetrates surfaces, making them brittle and unsightly. Cleaning costs increase significantly due to pigeon droppings, and without deterrent systems, facades are quickly soiled again.

Hygienic aspect:
Numerous diseases (see link to diseases page) are spread or caused by the presence or droppings of pigeons. These include infections caused by viruses (such as influenza and avian flu) and bacteria, many of which are harmful to humans.

Only effective and sustainable pigeon deterrence measures can mitigate these issues. Eradication or extermination is not a viable solution.
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