Though having no formal art training, Dr. Pratt is widely known as a zoological illustrator. His work has appeared internationally in periodicals and he has done 9 full-length books and contributed to others ranging from the National Geographic Society's Field Guide to the Birds of North America to the multi-volume Handbook of Birds of the World.

His most recent honor was completing the final plate for the posthumously published fifth edition of Roger Tory Peterson's Field Guide to the Birds. When not working in his office or studio, Dr. Pratt serves as a lecturer, ornithological consultant, and leader of nature tours worldwide.