Birds are rather fragile creatures and are susceptible to a number of ailments ranging from pests to disease to bullying by other birds. For most backyard bird keepers, an ailing or injured bird can turn your life upside down because of the intense amount of care often required by the bird. We've heard stories from some of our fellow chicken keepers where they literally took a sick chicken on vacation with them so they could administer its medicine two times a day. The chicken traveled around in a crate in the back of the car which of course caused complications relative to where the car could be parked and prompted precise instructions to the valet for when they needed to park their car at the high end restaurant where they would be dining.
For this reason, it is important to always keep a careful eye on your birds' behaviors to look for any deviations that could indicate a problem, so you don't get too far down the illness path to being with. In general, anytime you see a bird behaving differently from the norm, you can be highly confident there is something not right with the bird. Catching the situation early not only improves the bird's chance of survival, but also potentially prevents the spread of the issue to other birds. If a flock is kept in a clean area with quality food and water and plenty of space, you should not have many problems with your birds.
High quality food, fresh water and a clean environment with good air circulation and plenty of space for each bird are the bare minimum requirements to keep birds healthy. A secure place to roost with plenty of roosting space per bird will help minimize stress and help prevent bullying from birds who want "prime" roosting locations.
Always be very careful about introducing new birds to your flock. If you acquire new birds, it's best to keep them separated from the flock for two weeks and carefully watch for any signs of illness. Once you are confident your birds are disease free, you can introduce them to your flock by placing them in the coop at night after the other birds have gone to roost.
However, there will be times when you notice a bird is injured or is showing signs of stress resulting from being picked on by other birds. What we have found as a good solution for this is what we refer to generically as a "chicken hospital".
The structures can either have an open bottom that allows access to an earthen floor or you can put shavings in the bottom of an open or enclosed structure. The structures should be large enough to allow the bird enough room to move around, scratch and take a dust bath.
Food and water sometimes presents a bit more of a problem. Shavings are easier to clean up, but for hens that like to scratch a lot, you will often find you have to refresh their food and water at least twice per day. The earthen floor solution is a bit easier to keep clean, but if you need to move your hospital into an area such as your house, the enclosed floor is obviously preferred What we found works the best for waterers and food is small ceramic raised dog bowls. You can use a small bowl that's left on the ground, but it's typical the birds will dump it over and then may, or may not, eat the feed from the ground.
Water can be even trickier. Small plastic drinking fountains work, but large birds drink a lot of water, so going with a mid-sized or larger fountain typically works better. However, large drinking fountains also take up a lot of space in the hospital, impacting the space available for the bird. Here we found a bucket or bowl that's mid-height, or one that comes up to about mid-height on the bird's chest, seems to work best. Anything lower will quickly get dirty. Higher waterers might be difficult for less than healthy birds to access.
The key to recuperating any bird is to keep a careful eye on the flock, inspect and address any physical or behavioral changes in the bird immediately and keep the bird clean, dry and well fed while administering medications and/or allowing the bird to rest.
The hope is you will never need to use any of these measures, but chances are you will. Therefore, it's good to be prepared and have some sort of plan and structure available for when you need it. Time will be a critical factor when the situation does arise.