When you find a animal who is not itself assess whats wrong:

• Is it standing?

• Can it walk?

• Is its wing hanging or a leg lame?

• Is there swelling around the face?

• Any blood from wounds or orifices?

• Is it abnormally quiet and easy to catch?

If it falls under any of these categories they're probably suffered a

injury or is sick. This will mean it needs immediate care and pain

relief and possibly antibiotics if been in contact with a cat. This is

due to cats saliva containing bacteria that slowly causes

septicaemia and within 48 hours will kill the animal.

Do not offer it aspirin or human medicines this is likely to kill the 

animal. Contact your nearest rescue and get it over there asap.

Put them in a secure cardboard box with padding at the bottom

either

a towel or some soft bedding like straw to keep it contained safely.

Do not offer it food or water and keep it in a dark space with air holes

to prevent shock and allow it to remain in a stress free environment.