THE NORTH RIDING PROJECT

Of all the vultures, the black ones are the strongest.  No person has yet found a vulture’s nest: hence it is that there are some who have thought, though erroneously, that these birds come from the opposite hemisphere.  The fact is, that they build their nest upon the very highest rocks; their young ones, indeed, are often to be seen, being generally two in number.  Umbricius, the most skilful among the aruspices of our time, says that the vulture lays thirteen eggs, and that with one of these eggs it purifies the others and its nest, and then throws it away: he states that they hover about for three days, over the spot where carcases are about to be found.

Pliny/Natural History