PigeonsA Field Guide to the City Pigeon

Hold, then thrust

Filmed at high speed, a walking pigeon's head moves in two steps. In the hold step, the head stays almost locked in place while the body walks forward under it. In the thrust step, the head shoots forward to a new spot.

Compared with the body, the head seems to swing back and forth. Compared with the street, it only ever moves forward.

Researchers explain the hold as a way to keep the picture on the eye steady. The head is not perfectly still, though. A small slip remains, and researchers think it works as an error signal.

Eyes on the sides

A pigeon's eyes sit on the sides of its head. That gives it a very wide view, including much of what is behind it.

The cost is a small zone in front that both eyes see at once. Laboratory measurements show that zone is a narrow oval along the line of the beak.

Pigeons can also see near-ultraviolet light, which human eyes cannot see. In laboratory tests, pigeons trained to tell colours apart could also tell different ultraviolet light apart.

Sipping and pecking

Most birds scoop water into the lower beak, then tilt the head back so the water runs down the throat. A pigeon keeps its head down the whole time it drinks. Watch a puddle after rain and you may see the difference.

Pigeons mostly eat seeds and grains. Away from cities they eat waste grain, the seeds of grasses and other plants, and sometimes berries or acorns. They find their food by walking on open ground.

In cities, many pigeons also eat food people drop or hand out, such as bread crumbs and popcorn. How much each bird relies on scraps varies.

Bread fills a bird up but gives it very little of the goodness it needs. That makes it a poor food for pigeons.

What the crop makes

A hormone called prolactin makes special cells lining a pigeon's crop grow. Those cells form the crop milk that is fed to newly hatched chicks.

Prolactin is also the hormone that controls milk in mammals. In pigeon parents, high prolactin goes with eating more and staying at the nest, though how it drives those habits is still debated.

Field guides note that both parents feed the young this pigeon milk. So a pigeon chick has two milk-makers, not one.

Two eggs, two parents

A mother pigeon usually lays two eggs at a time, sometimes one. Because pairs nest many times a year, a pair lays far more than two eggs in a year.

Both parents take turns sitting on the eggs to keep them warm. The eggs hatch after about two and a half weeks; field guides give 16 to 19 days.

The nest itself is plain: a flat pile of twigs and grass. A pair may use the same spot again and again, adding to the nest each time.

Pairs and courtship

Pigeon pairs can stay together for life. Pairs can form at any time of year, and the two partners share most of the work of raising young.

To court a female, a male pigeon puffs up his chest, spreads his tail and struts in circles around her. He bows again and again, and coos.

A pair can raise several families of chicks in one year. City pigeons can breed in any season, and how often a pair nests depends a lot on food.

Hidden up high

Young pigeons, called squabs, often grow up out of sight on rooftops, towers and empty buildings. They stay in the nest until they are almost fully grown and look like adults.

Young pigeons usually leave the nest when they are about four weeks old, a little later in cold weather.

That is why people say you never see a baby pigeon. The London Museum calls this an urban myth. The young are there, just hidden, or almost adult in looks by the time they come out.

Cliffs made of buildings

City pigeons descend from wild rock doves. Rock doves nest in cracks and on sheltered ledges of sea cliffs and rocky gorges.

In cities, pigeons use buildings, window ledges, bridges and roofs instead. Museums, universities and bird groups all describe these as stand-ins for the birds' natural cliffs.

City pigeons are feral. They come from tame pigeons that escaped or were let go and now live on their own. In London, the first feral pigeons are traced to birds that escaped from dovecotes.

Wild rock doves are native to Europe, North Africa and southwestern Asia. Carried around the world by people, feral pigeons now live in cities worldwide.

Rock dove, feral, domestic

Pigeon or dove? There is no scientific difference. Both words name birds of one family, and people tend to call the smaller, more delicate ones doves. The rock dove and the feral pigeon are the same species.

Truly wild rock doves are getting hard to find. Where city pigeons arrive, the wild and feral birds breed together, and the feral birds take over. In crowded countries such as Britain, it seems unlikely that any true rock doves remain.

Domestic pigeons are the third group. People have bred hundreds of breeds, from fluffy fantails to tall pouters, yet all of them come from the one wild species.

Clues for finding home

Homing pigeons are domestic rock pigeons bred and trained to return to their home loft. Trained birds can return from long distances, including from release sites they do not know.

Far from home, scientists think homing pigeons can use the sun like a compass. The birds even allow for the way the sun moves across the sky during the day.

Near home, in familiar country, pigeons follow landmarks they know. GPS tracking showed that each bird tends to keep its own favourite route, and is drawn back to it even when released away from it.

Messengers and a famous story

Armies used homing pigeons because they could carry short notes in a tiny tube on the leg, back to their home loft. The most famous story comes from World War I.

In October 1918, a group of U.S. soldiers, later called the Lost Battalion, was trapped in France's Argonne Forest. A pigeon named Cher Ami is often credited with saving them.

The Smithsonian says it is certain that Cher Ami delivered vital messages and arrived badly wounded. But army records cannot show which pigeon carried the key message that gave the soldiers' location. So the famous story is partly legend.

Today, homing pigeons race. Trained birds are released far from home, and the one that flies home fastest over a measured distance wins.

The coat-swap test

The experiment ran in a city park in 2011. In the study, two people of similar age and skin colour fed the feral pigeons there, each in a different coloured coat. One stayed calm. The other chased the birds away.

Within six to nine visits, the pigeons learned to avoid the person who chased them. In later tests in the study, both people stayed calm, and the birds still avoided the chaser, even after the two swapped coats.

So the birds were not just reacting to a coat. The researchers suggest that, in the study, they used features of the person that stayed the same. The authors call it the first experimental evidence that feral pigeons tell people apart this well.

Paintings and words

In the study, pigeons were trained with slides of paintings by Claude Monet and Pablo Picasso. Afterwards they also sorted Monet and Picasso paintings they had never seen. Turning a Monet upside down threw them off, but turning a Picasso did not.

In the study of words, pigeons learned to tell real four-letter English words from made-up strings of letters. They could even spot real words they had never seen. They cannot read, though. They picked up on the letter patterns that make up words.

A bird and a mirror

The mirror mark test checks whether an animal notices a mark on its own body in a mirror. Pigeons do not pass it on their own. In the study, pigeons at first seemed to find hidden food by its reflection in a mirror.

With one eye covered, they walked at the mirror instead of the food. In the study, they had been seeing the food itself out of the corner of an eye.

Colour from structure

As the viewing angle changes, green neck feathers shift toward purple, and purple ones shift the other way. Females tend to show less shimmer than males.

The shimmer is not paint-like pigment. It comes from the tiny structure of each feather part, where light bounces within a very thin outer layer. A different thickness of that layer separates green feathers from purple ones. This is called structural colour.

Pigeon neck feathers also reflect ultraviolet light, a colour people cannot see but birds can. The researcher who measured it suggests birds may use such colours as hidden signals, but that use is only a suggestion.

Take-off

Startle a flock and some pigeons clap their wings together above their bodies as they take off. Not every pigeon claps on every take-off. Male rock pigeons also clap their wings in a courtship display flight, flying sharply upward near a female.

City pigeons are a favourite food of peregrine falcons, and plenty of pigeons helps peregrines live in cities.

A large family

There are about 300 kinds of pigeons and doves in the world. Most of them live in the tropics, where many eat fruit.

The dodo, a big flightless bird that is now extinct, was a kind of pigeon. Its closest living relative is the colourful Nicobar pigeon, which can fly.

The passenger pigeon, a cousin of the city pigeon, was once one of the most common birds in North America. Hunting and the loss of forests wiped it out. The last one, a captive female named Martha, died in 1914.

Darwin's pigeons

Charles Darwin kept every pigeon breed he could buy or obtain, and he belonged to a London pigeon club. In 1859 he argued that all the different breeds came from the rock pigeon.

He used the breeders' choices as evidence for his ideas about how living things can change over time.

Breeders have produced hundreds of breeds that differ in size, shape, feathers, colour and behaviour. One genome study counts over 350. Two breeds can differ as much as a German shepherd and a miniature poodle.

From loft to ledge

Pigeon racing is still a sport. Races are run by local clubs, where owners keep their own lofts, and as one-loft races, where all the birds live and train together.

The RSPB says the feral pigeons in towns and cities all descend from domestic pigeons that escaped or were released. Every city flock began with birds that once had a home loft or dovecote.

A watch from a bench

Choose a spot where pigeons are already feeding or resting. Sit still, far enough away that the birds do not need to move. Never chase, crowd or grab a pigeon, and leave nests alone.

Read the bird in a fixed order. Start with the neck and its green and purple shimmer. Then watch the walk for the hold and thrust of the head.

Actions are field marks too. Look for a bird drinking with its beak down, which most birds do not do. Look for a male bowing and cooing in circles. Listen as a flock lifts off, for some birds clap their wings.

A sample watch

Ten minutes by a fountain, written up. Saw: six pigeons. One neck flashed green, then purple, as the bird turned. Heads held still, then darted ahead. One bird drank with its beak down the whole time. A male bowed and cooed in circles. Guessed: a courting pair, fairly sure. A clap of wings as the flock lifted, cause unknown.

Six myths, checked

Myth: You never see baby pigeons. You do; you just may not know it. Young pigeons stay hidden in the nest until they are almost fully grown, then come out looking like adults.

Myth: A pigeon's head bobs back and forth. Compared with the street, the head only moves forward. It holds still, then thrusts ahead.

Myth: Pigeons and doves are different kinds of bird. Both words name birds in the same family, and the rock dove and the feral pigeon are one species.

Myth: Records prove which pigeon saved the Lost Battalion. Cher Ami's bravery is certain, but army records cannot show which pigeon carried the key message.

Myth: Bread is a good meal for a pigeon. Bread fills a bird up but gives it very little of the goodness it needs.

Myth: City pigeons are wild birds. They are feral. They come from tame pigeons that escaped or were let go.

Feature cards: field marks

Feature cards: one species, three lives

Kind habits

Keep your distance and stay still. If a pigeon walks or flies away, give it more room next time.

Leave nests alone. Young pigeons stay hidden until they are almost fully grown, and a nest on a ledge is a family at work.

Bread may look like a treat, but it is a poor food for pigeons. Their natural food is mostly seeds and grains.

Share what you see. A page of field notes from one bench is a fine way to show a friend a bird they walk past every day.