National Geographic announced Dr. Urquhart's discovery of the monarch's winter home in Mexico in the August 1976 issue of its magazine. He had been searching for their destination for nearly 40 years. Dr. Urquhart tagged his first butterfly in 1937. It took several hundred thousand tagged monarchs and the help of a large network of volunteers before the wintering sites were finally found in Mexico.

See: Discovery Tale: Two Clues Led the Scientists to the Monarchs