A giant elephant bird egg is to headline a natural history sale at Summers Place in Sussex, UK on November 26 with an estimate of £30,000-50,000 ($49,761-82,935).
The species was native to Madagascar and is believed to have been hunted to extinction by humans sometime between the 14th and 17th centuries.
The birds could grow up to 11 feet in height.
Errol Fuller, the curator for the sale, commented: "I have written several books on extinct birds and the Elephant Bird has always been particularly fascinating. The egg of one of these birds is simply a miracle, it's over a foot in length (30 cm) and larger than any known dinosaur egg.
"In fact it is the largest egg ever recorded and engineers have calculated that structurally and functionally it is impossible for an egg to be any larger."
A 12-inch example sold for £66,675 ($101,613) at Christie's New York in April last year.
A stuffed passenger pigeon, valued at £4,000-6,000 ($6,634-9,952), is also likely to prove a draw.
At one time the birds were among the most widespread in North America, but during the 19th century they were hunted on an industrial scale as a cheap source of food.
The last passenger pigeon, named Martha, died in Cincinnati Zoo in 1914.
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