Doves are members of the Pigeon family, distinguished as a doves, mainly by their smaller size. There are two groups of doves, those who eat seeds, and those who eat fruit. Most doves are seed eaters, and as such they tend to spend most of their time on the ground. I will refer mostly to the seed eating doves. Doves make graceful pets but are not a bird that will customarily sit on your shoulder or learn to "talk". They are often calm but can be easily spooked.

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Selection and Purchase
Doves will generally not be selected for bright colors, as they are often more subdued in color than other caged birds. They will not be selected for song, although their soft cooing is soothing and wonderful to listen to. As such you will most likely select your dove for its' subtleties of color, size, and charm.
Most doves are relatively inexpensive, but should be selected carefully. Most are monogamous, and will choose their own mate, thus if you desire a breeding pair you would be far better to buy directly from a breeder rather than from a store where you may get two opposite sex birds, but not necessarily a breeding couple.
Pet Stores, in general, are not considered the best place to look for any pet. They buy low and sell high, buying from breeders who may have substandard conditions, enabling them to produce massive numbers of birds at a lower cost. You are always better to find a quality breeder and purchase directly.
Never purchase birds from a facility where it does not appear they are cared for, not only are you risking getting unhealthy birds, but you are rewarding them for the poor condition of their facilities.
Look at the aviary conditions, are the birds over crowded? If so, there is a greater likelihood of disease or stress. If you buy an already stressed bird it may not survive the adaption to your home.
Pick a lively, happy looking bird, not one who is listless or dull. When the bird you have chosen is caught, flip it over in your hand, do not buy it if its' vent feathers are covered in white pastings, or are green, a sure sign of diarrhea. Ruffled or unkempt feathers may be a sign of parasites, such as bird mites.
Always ask for a warranty or health guarantee. The seller should be able to guarantee the health of the bird for at least one week, ideally two, after purchase.
Housing
Doves are often kept as house pets, or in warmer areas, are kept in outdoor aviaries. As they tend to spend much of their time on the floor of their cage, surface space is more important than height. Sadly most cages cater to people, rather than to the birds' needs, that is to say, that most cages are tall and narrow, rather than long. Make sure your cage also provides some perching areas, with perches of different diameters. If you are keeping your birds in an outdoor aviary it must have places with shelter from the wind, rain, and sun. If you are interested in breeding doves you will require nesting locations, which will need to be well off the ground.
If you are in a cooler climate your birds will need to be caged indoors for the winter.
Feeding and Care
Doves require a variety of seeds, you can usually purchase a dove mix, game bird food, or parakeet seed mix. If you plan on keeping many birds you may find it most economical to purchase your feed in larger bags from livestock feed stores.
Your dove will also need grit and water. The grit should be in its' own bowl separate from the food. You need to make sure the food bowl is always full, typically birds eat the seeds and leave the husks in their bowl. This gives the illusion that they still have food, so it should be checked regularly.
If kept in an indoor cage it will need to be cleaned weekly, if kept in an outdoor aviary, their aviary can be cleaned out twice a year. The birds themselves should be checked regularly for any sign of health problems or mites.
Other Tips
Moulting will occur in the mid to late summer, the birds will lose their feathers and these shall be replaced with new feathers.
Do not clip your birds wings, if you do not want a pet that can fly, do not get a dove.
Fruit doves are much less common, and I haven't really talked about their specialized care needs, they are much more difficult to care for than the seed eating doves.