It is often difficult or sometimes even impossible to catch a poorly or injured bird in need of help. Trying to capture a wild bird is a delicate endeavour. One must be certain not to harm the bird or damage its feathers, as the plumage is the most valuable asset of a bird. Feathers have many different functions apart from helping the bird to fly or swim. They are used for protection, insulation, waterproofing, camouflage, communication and display. Even minor feather damage can render birds unreleasable, or will at least delay their release by months if not a year. Swifts are a prime example, as these birds spend almost all of their life on the wing. Some animals in need of help are often still able to fly or to outrun a human. They might quickly disappear by going into hiding or by keeping themselves out of reach. Injured or poorly birds are also very likely to become distrustful and alert towards humans and their own kind, which makes rescue attempts even more difficult.