Answer
Care should be taken in buying animals or birds from adverts in the newspapers or online. Below are examples of steps that should be taken with respect to particular birds and animals.
Barn Owl - it is illegal to sell a barn owl that is not captive bred and close ringed. If you are thinking of buying a barn owl then it must be accompanied by an Article 10 certificate (issued by the Department for Environment Food and Rural Affairs) (DEFRA). The Royal Society for the Protection of Birds (RSPB) do not advocate the buying of owls as they do not make good domestic pets.
Bird of Prey - the same applies as with barn owls, the bird of prey must be ringed and accompanied by the Article 10 certificate. If the bird of prey is a Honey Buzzard, Golden Eagle, White Tailed Eagle, Marsh Harrier, Montagu's Harrier, Osprey, Goshawk, Peregrine Falcon or Merlin they must also be registered with DEFRA.
Tortoise – Depending on the species of tortoise you may again require an Article 10 certificate. If you are going to buy a tortoise make sure it is from a reputable breeder and a certificate (if required). Buying a tortoise is not as simple as it may appear as some are now endangered species. Please see the Tortoise Trust website in the related information, for further information on buying and caring for tortoises.