A ground bird's cage is measured in floor space
A diamond dove needs a cage at least 30 inches long by 18 inches wide by 18 inches high for a pair, and a 36-inch-long cage is a better daily life if you have the shelf for it. Height beyond that earns you very little, because a diamond dove is a ground dove: it walks, pecks, courts, and feeds on the floor, and uses perches mainly to rest and sleep. A tall cage sold for climbing parakeets wastes most of its volume above a dove's head while cramping the only dimension the bird truly lives in.
Bar spacing should be half an inch or less, since diamond doves are Australia's smallest dove and a slim bird can work its head into surprisingly narrow gaps, especially when startled into a sudden upward flight. That startle flight is also why the modest height still matters: a panicked dove launches vertically, and a cage with a little headroom and a solid, visible top is kinder than a cramped box it can strike at full speed.
Furnish the floor like a habitat, not a tray
Leave most of the floor open. Cover it with a clean, changeable lining you can refresh often, scatter a little of the daily seed ration across it so the pair can forage as they are built to, and add one flat shelf or platform and a couple of low, slim perches for roosting. Diamond doves do not climb bars to reach high dishes the way parrots do, so food and water belong low, in heavy shallow dishes that a walking bird will not tip, placed away from directly under the roosting perch.
A small, covered nest basket or sheltered corner suits a bonded pair, which may court and lay readily, but skip tall ladders, swings hung in the flight path, and deep piles of cage furniture. A diamond dove's exercise is a short, whirring flight from one end of the cage to the other, and every obstacle hung in that line shortens the only workout the bird gets indoors.
Pairs, placement, and a quiet room
Diamond doves are gentle and are almost always kept as a pair, whose soft, mournful cooing is quiet enough for most homes. Site the cage at about waist height in a calm room, where the birds can see people passing without feet and pets moving directly at their floor level all day, and where night is genuinely dark and undisturbed. A cage on the floor itself invites stress from above and close attention from dogs and cats, which a ground bird reads as predators approaching.
Out-of-cage flying needs more caution than with hookbills: doves cannot be coaxed back onto a hand as reliably, startle harder, and fly fast into windows. Many keepers give diamond doves their exercise inside a sufficiently long cage and a safe, enclosed flight rather than loose in a living room, which is another reason the cage length you buy at the start matters so much.
Buying checks for a dove, not a parakeet
In the shop, judge cages by usable floor area after the tray and dishes are in, measure the bar spacing yourself, and prefer a wide front door that lets you lift a dove out gently with two hands rather than chase it. Record your final cage length, floor covering, and dish placement in the pair's own notes, because with KinsLe's Transferrable Profiles a diamond dove that is rehomed later can hand its next keeper the exact long, low setup it is used to living on.