Which of the following is true?

A haggard hawk refers to a bird that has been fully fledged and is wild, distinguishing it from a juvenile hawk. An eyas is a young hawk that has not yet fledged and is generally still dependent on its parents. The statement about a haggard hawk being an eyas at one point is accurate because all mature hawks develop from the eyas stage.

Similarly, a passage bird is a term used to describe a bird that is in its first year of life, having fledged from the nest but not yet reached full maturity. This means that a passage bird was also once an eyas when it was still dependent and in the nest.

Given this understanding, both statements about the haggard hawk and the passage bird being at one time an eyas are accurate. Therefore, the choice that states both A and C are true reflects the correct understanding of these developmental stages in hawks.