Avalerion

An avalerion or alerion is a mythological bird. It was "rather small, yet larger than an eagle" and lived near the Hydaspes and the Indus according to European medieval geographers and bestiaries, which were possibly based on a description by Pliny. Only two of the birds were said to exist at a time. A pair of eggs was laid every 60 years; after hatching, the parents drowned themselves.