Through field work in New York, Wyoming and Mexico, and in collaboration with Hamilton students, Williams studies the population biology, chemical ecology, and conservation of butterflies. His most recent book is The Nature Handbook: A Guide to Observing the Great Outdoors, which is a field guide to patterns in nature and was released in 2005 by Oxford University Press. He is also co-author of The Stokes Butterfly Book, published by Little, Brown and Co., and editor and co-author of A Marsh for all Seasons, published locally by the Utica Marsh Council. His recent publications have appeared in Journal of Insect Conservation, Journal of the Lepidopterists' Society, the Journal of Animal Ecology, Resoration Ecology, The Journal of Biogeography, and American Butterflies. Williams currently works with Associate Professor of Biology Bill Pfitsch on habitat restoration and management in the Rome Sand Plains of central New York.