Wear gloves. When dealing with waterfowl, a thick pair of work gloves can prevent personal injury. A net is very useful for capturing animals that will try to flee or fly. If a body of water is nearby, get between the water and the animal. If the bird is not flighted, you can try to herd it towards an area like a wall or bush where you can more easily catch it.
Prepare a container
A large crate or large box with air holes, lined with newspaper or a sheet/towel will work for most large birds.
Put the bird in the box
Cover the bird’s head with a towel, keep the wings tucked into the body, and always be careful of its bill and wings. Immediately close the box.
If you can’t transport it immediately
Keep the bird in a warm, dark, quiet place.
Do not give it food or water. Feeding an animal an incorrect diet can result in injury or death. Also, a captured animal will get food and water stuck in its fur/feathers potentially leading to discomfort and hypothermia.
Do not handle it. Leave the animal alone. Remember human noise, touch and eye contact are very stressful to wild animals.