Pigeons and doves exhibit considerable variations in size. The largest species is the crowned pigeon of New Guinea, which is nearly turkey-sized, at a weight of 2–4 kg (4.4–8.8 lb) The smallest is the New World ground-dove of the genus Columbina, which is the same size as a house sparrow and weighs as little as 22 g. With a total length of more than 50 cm (19 in) and weight of almost 1 kg (2 lb), the largest arboreal species is the Marquesan imperial pigeon, while the dwarf fruit dove, which may measure as little as 13 cm (5.1 in), has a marginally smaller total length than any other species from this family.
Overall, the Columbidae tend to have short bills and legs, and small heads on large, compact bodies. Their characteristic head bobbing was shown to be due to their natural desire to keep their vision constant in a 1978 experiment by B. J. Frost in which they were placed on treadmills – they did not bob their heads as their surroundings were constant. The wings are large and have low wing loadings; pigeons have strong wing muscles (wing muscles comprise 31–44 % of their body weight) and are among the strongest fliers of all birds. They are also highly manoeuvrable in flight.
The spotted dove, which is most commonly found in Southeast Asia
The plumage of the family is variable. Granivorous species tend to have dull plumage, with a few exceptions, whereas the frugivorous species have brightly coloured plumage. The Ptilinopus fruit doves are some of the brightest-coloured pigeons, with the three endemic species of Fiji and the Indian Ocean Alectroenas being the brightest. Pigeons and doves may be sexually monochromatic or dichromatic. In addition to bright colours, pigeons may sport crests or other ornamentation.
Like some other birds, the Columbidae have no gall bladders. Some medieval naturalists concluded they have no bile (gall), which in the medieval theory of the four humours explained the allegedly sweet disposition of doves. In fact, however, they do have gall (as Aristotle already realised), which is secreted directly into the gut.
Pigeons and doves are distributed everywhere on Earth. The family has adapted to most of the habitats available on the planet. These species may be arboreal, terrestrial, or semiterrestrial. Various species also inhabit savannas, grasslands, deserts, temperate woodlands and forests, mangrove forests, and even the barren sands and gravels of atolls.
Seeds and fruit form the major component of the diets of pigeons and doves. In fact, the family can be divided into the seed-eating or granivorous species (subfamily Columbinae) and the fruit- and mast-eating or frugivorous species (the other four subfamilies). The granivorous species typically feed on seed found on the ground, whereas the frugivorous species tend to feed in trees. There are morphological adaptations that can be used to distinguish between the two groups; granivores tend to have thick walls in their 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 to reach fruit.
In addition to fruit and seeds, a number of other food items are taken by many species. Some, 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 fruit doves and ruddy ground doves.