The appraised work appears to be a mixed media (possibly watercolor and gouache) work on paper by American artist William Zimmerman (1937-2011). In the tradition of other ornithologist artists like John James Audubon, Zimmerman illustrated important texts like The Birds of Indiana and Waterfowl of North America among others. He is known for a precision and meticulous rendering of both bird illustrations and other wildlife subjects. The estimate provided is based on comparables recently offered and sold at auction. In may cases, pricing for similar examples available on the primary (retail) market vary, and are often higher than secondary (auction) market examples.