Answer:
Different lights do make me strange, thus into different sizes I will change.
A hill full, a hole full, yet you cannot catch a bowl full.
Until I am measured I am not known, Yet how you miss me when I have flown.
I have four legs but no tail. Usually I am heard only at night.
They can be harbored, but few hold water. You can nurse them, but only by holding them against someone else. You can carry them, but not with your arms. You can bury them, but not in the earth.
What covers its face with its hands, speaks no language, yet most known what it's saying?