The newspaper said a committee of scientists and executives reported earlier this year the collection could bring about $50 million. The museum owns what some experts say is the best set of John Audubon's "Birds of America" as well as other rare items documenting the natural history of the United States.
In 2004, the museum sold more than 30 paintings by George Catlin, a 19th-century artist who specialized in the American West, especially portraits of American Indians. Scholars say the works have disappeared into private collections.
The museum said in December that significant budget cuts would be necessary after a decade of expansion and recently announced staff reductions.