You might think a baby bird needs help, but it may just be the bird is learning how to fly. Watch the bird for a while from a distance to establish it really is injured and has been abandoned by the mother.  Look for feathers. If a baby bird has feathers, it is likely learning to fly.  You can put featherless baby birds back in the nest if they're not injured. If a bird feels cold, warm it in your hands before setting it back in the nest. The scent of your hands will not bother the parents, who will feed it as they do the other babies.   If you don't see a nest, put the bird somewhere where it is hidden from cats and dogs. For instance, you can set it in a bush or tree. If you see a gaping wound, that is an indication an adult bird needs help, and you may need to rescue it. Blood is another indication a bird is in trouble. If the bird is dripping blood or if you see dried blood, it may need help. If the bird is having trouble standing or flying, it is in serious trouble and needs help. It may be best to leave the bird where it is until you can get help from a professional. Big birds, such as hawks, can cause you serious harm if you don't know what you're doing.

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Write a summary of the previous text in Chinese:
确认鸟的大小。 如果是一只成年的鸟，看看它身上有没有伤口。 检查一下周围有没有血迹。 看看它的动作。 三思而后行。