In the heart of the city, an unassuming investigator works tirelessly. The Rock Pigeon. To some, he is an honorable battlefield messenger. To others, he is nothing more than a “rat with wings”.

To me, he’s something more important. He breathes the air we breathe, and he collects the dust of our sidewalks on his feathers. With each flap of his wings, he’s collecting data. He’s not just another face in the crowd; he carries clues that could help us tackle our pollution problem.

A flock of Rock Pigeons (Falcon Environmental Services).

Distribution

Year-round Rock Pigeon distribution across Africa and Eurasia (Birds of the World).

Rock Pigeons (Columba livia), originally from Europe, North Africa, and parts of Asia, were brought to North America in the early 1600s by colonists. These birds were already domesticated through human breeding, but quickly adapted to life in the wild and spread throughout the continent. People tend to call them “feral pigeons” in North America, but they are the same species as the original wild Rock Pigeon (Birds of the World).

In North America, Rock Pigeons are most common in cities and near farms. You usually find them close to people, but they have been spotted in remote areas of British Columbia, nesting on cliffs or bridges. They’re extremely widespread, even living on islands like Bermuda and Hawaii, and northern regions such as Alaska and the Yukon (Birds of the World).

Year-round Rock Pigeon distribution across North and South America (All About Birds).

Identification

A beautiful Rock Pigeon standing on a fence (iNaturalist).

Most Rock Pigeons are bluish-grey with darker shades on their head and rump. However, some may be bluish-black, rusty red, or mostly white. They usually have two dark bars on each wing, a blue-black band across the tail, and an iridescent green and purple neck. They also have bright orange eyes! Males are more colourful, while females and juveniles tend to be duller. (Birds of the World).

Rock Pigeons vary in size and colouration depending on where they live. In general, pigeons that live in dry areas are usually paler, and those that live in colder areas are larger.

Rock Pigeon flocks often have mixed colours, which makes them easy to tell apart from other pigeon flocks, like the Band-Tailed Pigeon. The diagram on the right shows different colour morphs of a typical city Rock Pigeon. However, there are eight other subspecies, in Africa and Asia, that are categorized by size and colour patterns. An example is the Mauretanian Rock Pigeon from West Africa, who has a darker body with red skin patches around the eyes (Birds of the World).

Possible feral pigeon colour morphs (ScienceDirect).

Example of photos shown to feral pigeons. Pigeons were able to recognize faces they’d seen before (Claudia et al., 2012)

Pigeons can recognize and remember human faces! In a study at the University of Vienna, pigeons were trained to distinguish between photos of people they frequently encounter and photos of strangers. They were able to recognize familiar faces, even with different clothes, photo angles, and lighting! (Claudia et al., 2012)

Habitat

Wild Rock Pigeons like to nest in rocky crevices along seaside cliffs or mountains. They especially like areas with open vegetation or farmland, as opposed to forested areas.

North American feral Rock Pigeons like to nest on human-made structures that remind them of cliffs. Think farm buildings and skyscrapers! Cities and farms also provide pigeons with easy access to food. Who could refuse a bed and breakfast? (Birds of the World).

Just like humans, some pigeon parents are better than others… (Reddit)

A general video about how animals may use magnetic fields for navigation. HINT: We now know- they use cryptochromes!

Sounds & Behaviour

Rock Pigeon primary song (All About Birds)

Rock Pigeon nest call (All About Birds)

Rock Pigeon wing-clapping (All About Birds)

Rock Pigeons are relatively quiet, but they have a few identifiable calls. The first is their primary song, which is a complex “coo, roo-c’too-coo” sound. This song is used for attracting a mate and establishing territory.

They also have a nest call, which is done on or near the nest, and is typically for advertising to a mate. It is a softer “oh-oo-oor” sound.

Rock Pigeons also communicate by flapping their wings. After mating or during other display flights, they will clap their wings together on the upstroke (Birds of the World).

Both male and female Rock Pigeons will defend their nest site. Males tend to go a little further and chase or peck intruders. Interestingly enough, the pigeons tend to choose mates of different colour patterns than them. Like many other birds, they mate for life- how sweet!

Feral pigeons flock together in colonies of up to 1000 birds. Imagine that many birds trying to feed in one area! In a feeding frenzy, they can often be shoulder-to-shoulder, but they do try to stay spaced enough to avoid pecking each other (Birds of the World).

Rock Pigeon display flight with wing-clapping (J. Zickefoose)

Pigeons can differenciate between the art styles of Monet and Picasso! (Reddit)

Pigeons can recognize art styles! Researchers trained pigeons to distinguish between art from Monet and Picasso. Once trained, they could identify which artist a painting belonged to, even if it was one they’d never been shown! This means they recognized the art style, not the painting itself. They were even able to recognize which artists had similar art styles- they identified paintings by Cézanne as being similar to Monet, and paintings by Braque as similar to Picasso! (Watanabe et al., 1995)

Conservation

In North America, only 43% of Rock Pigeons make it to 50 days old. Feral pigeons live 2.4 years on average, but a retired U.S. Army Signal Corps pigeon lived to 31 years!

Pigeons can carry diseases, such as aspergillosis and influenza. They commonly get mites, feather lice, and protozoans, all of which can be deadly. Despite this, high populations are found in Northern cities. Vancouver, B.C. houses around 15,000 feral pigeons!

Rock Pigeons are not globally threatened. Our main concern is that many natural Rock Pigeon populations are interbreeding with feral pigeons, who were originally domesticated. This could cause us to lose our wild Rock Pigeons over time (Birds of the World)

U.S. soldier holds a carrier pigeon, Italy, 1943 (WW2 Online)

They’re doing so well that they’re considered pests in some areas, especially on farms where they could spread disease to other animals. Methods like trapping, shooting, and using toxic baits are sometimes used to reduce populations.

Toxic bait can be harmful to predators that eat pigeons. It is often passed on and results in killing the predator too. Instead, we can use natural relationships between prey and predator to deter pigeons from certain areas. Using large raptor decoys can prevent pigeons from nesting nearby. Flying falconry birds regularly in an area can also deter prey birds, and this is often utilized in larger cities.

So what do pigeons have to do with pollution?

Pigeons can act as bioindicators for lead pollution. A bioindicator is a living thing that helps scientists monitor the health of an environment. Pigeons live in the urban environment with us, and share our food sources, air, and space. This makes them great bioindicators for how healthy our cities are, and therefore- how healthy we are!

An urban environment (Data-Driven EnviroLab).

Toxic effects of lead on humans (Geneva Environment Network).

Lead is a toxic heavy metal that was used in things like paint and gasoline up until a few decades ago, when most lead products were banned. Lead still exists in our cities, in old painted buildings and roadside residues.

Lead exposure is harmful to humans, even at very low levels. It’s especially harmful to children, and can affect brain development, memory, intelligence, and social skills (Cai & Calisi, 2016).

A study done in Korea looked at how much lead was on unwashed feathers of feral pigeons. Pigeons from industrial (more polluted) areas had 2-4 times more lead on their feathers than pigeons from rural areas! This means that unwashed pigeon feathers can help us figure out how much lead is in our air (Dong-ha et al., 2004).

Pigeons are ground-feeders, which means they consume small amounts of rock and soil that might contain lead. In Broken Hill, Australia, they looked at the amount of lead in the blood of Rock Pigeons. Blood lead levels were significantly higher in areas closer to mining activities! Not only that, but elevated blood levels in the pigeons reduced their ability to get oxygen, leaving them tired and with weakened immune systems (Gillings et al., 2024).

The Broken Hill zinc-lead ore deposit (Wikimedia).

New York City (Britannica)

In New York City, researchers looked at the blood of feral pigeons over a five year period. Pigeons in some neighborhoods, like Soho and Greenwich Village, had higher blood lead levels than pigeons in other areas, like the Bronx and North Queens. This means pigeons can help us figure out which specific areas have pollution problems!

They also found a positive correlation between the blood lead levels of pigeons and children in NYC. This means that where pigeons were at risk, children were also likely to be at risk (Cai & Calisi, 2016).