British Library, Additional MS 42130, Folio 159r.Pliny says [1st century CE] (Natural History, Book 10, 9-10): There are 16 varieties of hawks. They eat other birds, though not the heart. Some catch only birds that are on the ground, others only those flying around a tree, others only birds perched in a tree, still others only those flying in the open. Doves recognize the type of hawks they see, and land of the ground or fly in the air to be counter to the particular hawk's habits, and so save their lives. Hawks are used to assist men in catching birds; the men and the hawks share what they catch.