These are the oldest references to Mother Carey I can find:


(1) From An Historical Account of All the Voyages Round the World Performed by English Navigators (London: F. Newbery, 1773), page 121:

During this time they saw abundance of sea birds, among which were two sorts, one like a pigeon, which the seamen called the Cape of Good Hope Hen; and the other Mother Carey's Chickens; but the true name of these latter is the Peterel.


(2) From A Voyage to the Pacific Ocean by James Cook (London: W. and A. Strahan, 1784), page 86:

The Cape petrel, or Pintado bird; the small blue one, which is always seen at sea; and the small black one, or Mother Carey's Chicken, are not here in great numbers. But we found a nest of the first with an egg in it, about the size of a pullet's; and the second, though scarce, was met with in some holes like rabbit-burrows.

Another sort, which is the largest of all the petrels, and called by the seamen Mother Carey's Goose, is in greater numbers; and so tame, that at first we could kill them with a stick upon the beach. They are not inferior in size to an albatross, and are carnivorous, feeding on the dead carcasses of seals or birds, that were thrown into the sea. Their colour is a sutty brown, with a greenish bill and feet; and, doubtless, they are the same that the Spaniards call quebrantahuessos, whose head is figured in Pernetty's Voyage to Falkland Islands.