After nearly three years of infighting and courtroom skirmishes, a library on Thursday will auction off its most valuable holding — John James Audubon's celebrated "The Birds of America."

The Providence Athenaeum is among several nonprofit institutions that have turned to selling their most prized art to cope with financial struggles.

The collection of 435 color engravings of birds in the wild, based on Audubon's drawings, should fetch between $5 million and $7 million, according to Christie's, the New York auction house conducting the sale. Christie's calls it the finest color plate book of ornithology ever produced.

The collection of etched, hand-colored prints is especially valuable because it's a complete collection, in excellent condition and because the library was an original subscriber to the work, which was completed in 1838. There are fewer than 120 known complete copies of Audubon's masterwork, according to Christie's.

Another complete copy of "Birds of America" was sold by Christie's for $8.8 million in 2000, a record for a printed book sold at auction.

The Athenaeum, the fourth-oldest library in the United States, was less than a year old when its board voted to buy the work. It is selling the prints to raise money for its endowment, which the institution has tapped in recent years to pay for building repairs and to cover higher expenses.

The library's board ignited an uproar when it decided in February 2003 to sell the collection.

A group of members and shareholders took the library to court to stop the auction, but a judge ruled in the library's favor and the state Supreme Court upheld that decision in July.

Betty Rawls Lang, president of the private library's board of directors, said it's tough raising money for a literary these days.

"When you say, 'Would you give to a library?' they say, 'Well, you know, I will give to the latest tragedy or to cancer.' It's a difficult sell in a way," she said.

Last month, the New York Public Library auctioned a portrait of George Washington for $8.1 million and sold other art objects to raise money for its endowment.

The Heckscher Museum of Art in Huntington, N.Y., had planned to sell George Grosz's "Eclipse of the Sun" to a private collector for $19 million to help fund an expansion, but this year scuttled the plans under criticism.

Early this year, the Rhode Island Historical Society said it would have to sell an important Colonial-era desk and bookcase to help offset financial problems caused at least in part by its evaporating endowment. The sale was put off when someone donated $750,000.