The Australian White Ibis was once commonly called Sacred Ibis. It's a bird often seen in large numbers at rubbish tips so the name seemed to me incongruous, but the following passage from a book by J A Leach goes a long way to explaining its origins:
...Amongst the world's birds, few are better known than the Ibis. This bird was so highly prized by the ancient Egyptians as to be considered sacred, and they thought enough of it to embalm it. As Egypt depended on the overflow of the Nile for food supply, and as this overflow was heralded by the arrival of the migratory Ibis from the South, it was natural for the Egyptians to connect the rise of the river with this bird, and thus look for its approach. Again, the Ibis is an insect destroyer, and, as Egypt was subject to plagues of grasshoppers, it undoubtedly rendered as valuable service there as it does here. This is another reason that has been assigned for the esteem in which this valuable bird was held. However, it is now almost unknown in Egypt.
In Australia we have three Ibises. One, the Sacred Ibis, or White Ibis, is practically identical with the Sacred Ibis of Egypt.*
*An Australian Bird Book, 1912, 2nd Ed. p52.
by J A Leach, M.Sc (1870-1929).