Orn
From the back cover:

Three humans and an extraordinary alien creature in a quest across the fave of a counter-earth in turmoil:

Cal is a wise and courageous old man whose courage overcomes his wisdom in a deadly encounter with a towering and majestic monster.

Veg is a strong and sensitive man whose total loyalty to the exploration team is fearfully tested in the wilds of the killer planet.

Aquilon is a beautiful your woman, an artist and an adventurer, who forms a strange and beautiful friendship with a creature who cannot speak to her.

Orn is a great, powerful and lethal bird -- a bird with a subtle and fascinating alien intelligence and a surprising and unique purpose in existence.
American Science fiction, Prehistoric animals, Fiction, Space exploration, Aliens (Non-humanoid)
Piers Anthony
Piers Anthony was born in Oxford, England.  When he was four years old, his family immigrated to the United States.  He graduated from Goddard College in Vermont in 1956, the year he met and married his wife, Carol Marble.  After working at odd jobs, he joined the U.S. Army in 1957 for steady income and medical insurance.  In 1958, he became a U.S. citizen.  He became an editor and cartoonist for the Battalion newspaper.  He left the army in 1959 and briefly taught public school before becoming a full-time writer.  Anthony currently lives with his wife on a tree farm which he owns in Florida.