Why do pigeons bob their heads when they walk?

Most evidence suggests that the head bobbing serves a visual function.

See video: http://in.youtube.com/watch?v=NHtrsbw3K0g

This has always been an intriguing phenomenon. Pigeons (or ‘Rock Pigeons’ to be exact) have a peculiar habit of bobbing their heads up and down when they walk. This leads to a common misconception – that the legs of a pigeon are somehow connected to their heads. When they walk, they move their heads up and down; when they stand still, there is no movement!

Birds have eyes on either side of their head, so don't have stereoscopic vision. In order to see depth, they take snapshots with the same eye from two points, and their mind makes the depth calculation.

In order to shed more light on this conundrum, one must first understand the basics of ‘bird vision’. From Ornithology (the science of birds), it can be inferred that as the pigeon’s eyes are on the side of its head – allowing a greater range of vision to stay vigilant against predators from all directions – they also disable the pigeon from its sense of depth. Pigeons cannot establish distances easily. Luckily we humans have eyes on the front of our heads, giving us depth perception.

For the pigeon to compensate this shortcoming, the bird moves its head, deciding on differences in apparent motion from nearby and/or distant objects. Closer objects move faster, distant objects move slower.

Now when rock pigeons stop in one place, there is no requirement for depth perception, hence the cessation of the head bobbing. But once they start foraging for food again, the need for depth kicks in and they start moving their heads up and down – giving the illusion that their heads are somehow connected to their feet!

To illustrate this concept, here is a common example: In the past, you may have tried to shoo away a pigeon in an outdoor picnic area. When a hand is wafted towards the pigeon, it turns sharply head first – in a desperate attempt to ascertain the depth of the attack – before attempting to fly/walk away. It all happens very quickly, but look out for it next time!

Chickens bob their heads while walking. So do cranes, magpies and quails. In fact, head bobbing is a unique feature in birds and occurs in at least 8 of the 27 families of birds.

There are a few theories why some birds bob their heads when they walk:
1. Assists with balance
2. Provides depth perception
3. Sharpens their vision

However, most studies suggest that birds in motion bob their heads to stabilize their visual surroundings. In comparison, we rely more on our eye movements, not our head movements, to catch and hold images while in motion.

Picture a pigeon on a moving treadmill. What do you think would happen as the pigeon walks with the speed of the treadmill and its environment remains relatively the same? Dr. Barrie J Frost (1978) did this experiment and the pigeon’s head did not bob.

Dr. Mark Friedman (1975) also conducted a series of experiments to test the head bobbing actions of birds, using doves. His research demonstrated that the head movement is controlled more by visual stimulation than movement of the body.

Scientists continue to research head bobbing in birds. For example, scientists are currently investigating question such as “Why do some birds exhibit head bobbing, while other do not?” For more information on this topic see the related Web sites section.

Domestic, Feral or Rock Pigeons

Pigeons are actually domesticated rock doves that have returned to wild or semi-wild conditions. Some rock doves were domesticated for food, others as homing pigeons, and some as ‘fancy’ pigeons, bred for their plumage. Feral pigeons, also called city doves, city pigeons or street pigeons, are derived from domestic pigeons that have returned to the wild. The domestic pigeon was originally bred from the wild Rock Pigeon, which naturally inhabits sea-cliffs and mountains. All three types readily interbreed. Feral pigeons find the ledges of buildings a perfect substitute for sea cliffs, and have become adapted to life and are abundant in towns and cities all over the world.

Life span: They average 3-5 years in the wild. Captive pigeons can live for 15 years but some have been known to live for up to 35 years.

Statistics: Length: 29-33cm, Wingspan: 60-68cm.

Physical description: Feral pigeons are a generally grey bird with slightly iridescent feathers on the neck that shine pink and green in the sunlight. Coloration is very variable with some individuals being white, others brownish-red, some grey and many mixtures. The eyes are orange and shine brightly in the sunlight.

Distribution: Feral pigeons are widespread and very common throughout Europe. They are also found in Africa, North America, South America and Asia.

Habitat: They inhabit coastal cliffs or buildings in towns and cities.

Diet: Wild rock doves feed on seeds but the diet of the pigeons has grown to include bread, vegetables, meat and other food discarded by humans. Pigeons are not generally fussy eaters, they have only 37 taste buds (humans have around 10,000).

Behaviour: Pigeons feed on the ground in flocks or individually. They roost together in buildings or on walls or statues. When drinking, most birds take small sips and tilt their heads backwards to swallow the water. Pigeons are able to dip their bills into the water and drink continuously without having to tilt their heads back. When disturbed, a pigeon in a group will take off with a noisy clapping sound. This helps inform the other pigeons that there is danger present. If a pigeon is alone it will respond to danger by keeping very still and trying not to be noticed. Pigeons are excellent fliers and can reach speeds of up to 50mph. They are capable of rapid dives and changes in direction and most of the time will easily out manoeuvre a bird of prey such as a sparrowhawk. They are resident and do not migrate.

Reproduction: During courtship the male will follow a female around bowing his head, fanning his tail and making ‘cooing’ noises. Eventually a short dance begins with the male’s beak being held in the female’s. Mating occurs shortly afterward and is fairly brief. The male sits on the female’s back flapping his wings to keep balance. It may take several clumsy attempts before the male successfully mates with the female. Nests are built by the female using material collected by the male. The female lays clutches of two white eggs. Young pigeons are known as ‘squabs’. They are fed from a special substance produced in the pigeon’s crop known as ‘pigeon milk’. This substance is high in fat and protein and low in carbohydrate.

Conservation status: Feral pigeons are very common and widespread, their wild cousins in Britain, however, are limited to the west coasts of Scotland and Ireland. In Northern Europe they are limited to the coast of Brittany in France. They are more widespread in the Mediterranean.

Pigeons and Doves

Pigeons and doves constitute the family Columbidae within the order Columbiformes, which include some 300 species of near passerine birds. In general parlance the terms "dove" and "pigeon" are used somewhat interchangeably. In ornithological practice, there is a tendency for "dove" to be used for smaller species and "pigeon" for larger ones, but this is in no way consistently applied, and historically the common names for these birds involve a great deal of variation between the term "dove" and "pigeon." This family occurs worldwide, but the greatest variety is in the Indomalaya and Australasia ecozones. The young doves and pigeons are called "squabs".

Pigeons and doves are stout-bodied birds with short necks and short slender bills with a fleshy cere. The species commonly referred to just as the "pigeon" is the feral Rock Pigeon, common in many cities.

Doves and pigeons build relatively flimsy nests from sticks and other debris, which may be placed in trees, on ledges, or on the ground, depending on species. They lay one or two eggs, and both parents care for the young, which leave the nest after 7 to 28 days. Doves feed on seeds, fruit and plants. Unlike most other birds (but see flamingo), the doves and pigeons produce "crop milk," which is secreted by a sloughing of fluid-filled cells from the lining of the crop. Both sexes produce this highly nutritious substance to feed to the young.

Diet

Seeds and fruit form the major component of the diet of pigeons and doves. In fact, the family can be divided into the seed eating or granivorous species (subfamily Columbinae) and the fruit eating or frugivorous species (the other four subfamilies). The granivorous typically feed on seed found on the ground, whereas the species that feed on fruit and mast tend to feed in trees. There are morphological adaptations that can be used to distinguish between the two groups, granivorous species tend to have thick walls in the gizzards, whereas the frugivores tend to have thin walls. In addition fruit eating species have short intestines whereas those that eat seeds have longer ones. Frugivores are capable of clinging to branches and even hang upside down in order to reach fruit.

In addition to fruit and seeds a number of other food items are taken by many species. Some species, particularly the ground-doves and quail-doves take a large number of prey items such as insects and worms. One species, the Atoll Fruit-dove is specialised in taking insect and reptile prey. Snails, moths and other insects are taken by White-crowned Pigeons, Orange Doves and Ruddy Ground Doves.