In this recent article in Backyard Poultry, author Harvey Ussery isn’t crowing about his own extensive knowledge about brooding chicks. He’s far too humble for that.
No, Ussery would like to direct your attention to the real experts at raising baby birdies — mother birdies! Hens, in this case.
To become an expert at brooding just-hatched chicks, learn from an expert: Spend some time watching a mother hen to see how efficiently she provides for all her babies’ needs. The chicks’ down doesn’t insulate them as well as their eventual feathers, so—should it get breezy—the hen calls them to huddle under her breast and wings for some on-the-spot warming. If a rain shower blows up, she finds dry shelter. She spends most of her time finding high-quality natural feeds for her chicks, ensuring rapid growth and excellent health. Finally, the hen will defend them from predators looking for a meal. (I have seen one of my Old English Game hens thrash a Cooper’s hawk trying to grab one of her chicks. When that whirlwind of fury hit, the hawk’s only concern was finding something to do somewhere else—anywhere else.)
Those lessons from a pro mostly sum up all we need to know about brooding chicks until they are well feathered, less vulnerable, and ready to take care of themselves: Keep them warm and dry. Protect them from predators. And feed them as diverse an array of live, natural feeds as you can, from day one. If your brooder and your management meet these requirements, brooding chicks is easy and success is virtually certain.
The BrooderI will assume that you’re brooding at the home scale, say somewhere between 25 and 100 chicks at a time. For brooding at this scale, set-up can be simple indeed. Most home flocksters do not maintain a permanent, dedicated brooder, but simply set up a temporary one for the three or four weeks needed. We brooded our first batch of 25 chicks, for example, in the carton in which a new refrigerator had been delivered, parked temporarily in our shop. (Do note, though, that by the end of the brooding period there was a coating of dust everywhere in the shop!) Most flocksters use electricity to warm the brooder, so a convenient outlet is a better option than a long set of extension cords, which creates hazards. A basic layout: A friend of mine simply blocks off the end of a small tool shed with a thin plywood barrier as a temporary brooder space. Another blocks off a corner of a horse stall in her barn using straw or hay bales, and tops it off with a mesh gate to keep the chicks inside and protect them from intruders. It is essential that the brooder be well ventilated, to allow for constant air exchange. At the same time, a direct air draft on the chicks can chill them dangerously. The compromise between the two needs is ensuring there is no draft at floor level where the chicks are, but providing plenty of air flow above them. Abundant ventilation is not only necessary to ensure constant fresh air for the chicks—it helps as well keep the brooder dry, preventing health problems related to damp conditions. Many flocksters employ a “draft shield” to block drafts at floor level, perhaps a long strip of cardboard 12 to 18 inches high, set in a circle around the space under the heat source, or a long strip of metal flashing which gets rolled up and stored until the next batch of chicks. In either case, the draft shield should be expanded as the chicks grow and need more space. In addition to blocking drafts, a draft shield prevents right-angle corners in the brooder in which chicks can “pile up” if cold, frightened, or otherwise stressed, leading to suffocation in the worst case. Avoiding sources of stress is better than providing solutions, of course. I have never used such a circular shield and have never had a problem with piling up. The usual source of heat for the chicks is either an electric heating element or heat lamps, suspended overhead. Heating elements with a rheostat for dialing temperature up or down are readily available from poultry supply houses. If you rely on lamps, it’s better to use two, so heat remains available even if one burns out. My farm co-op offers both 150-watt flood lamps and 250-watt heat lamps, either of which screws into the same shiny metal reflector hood with porcelain base. Some flocksters prefer an infrared heat lamp, others opt for heat lamps with ordinary clear light. I’ve used both and have seen little difference in performance. Whether suspended or clipped to a handy anchor, the lamp must be securely attached to prevent falling onto a combustible surface. Heat lamps (250 watts) should be no closer than 18 inches, 125- or 150-watt lamps no closer than 13 inches, from a flammable surface underneath. There should be no danger of accidental wetting of bulbs, sockets, or plugs. Read the rest of the article  for detailed information on how to raise chicks.