John Thayer

John Eliot Thayer (April 3, 1862 – July 29, 1933) was an American amateur ornithologist.

Thayer was born in Boston, Massachusetts, the son of Nathaniel Thayer, a banker who built Harvard's Thayer Hall. After graduating from Harvard, Thayer married Evelyn Forbes and settled at the family farm at Lancaster, thirty-five miles west of Boston. He became interested in ornithology in the mid-1890s, building up a collection which he housed in a museum in the main street of Lancaster.

He used his wealth to sponsor various natural history expeditions and in 1906 he sent Wilmot W. Brown to Guadalupe Island off Pacific Mexico. Here, Brown, H. W. Marsden and Ignacio Oroso gathered field data on how the natural vegetation was being destroyed by thousands of goats, to the detriment of the native wildlife. The native Guadalupe storm petrel was being predated by introduced cats, as was the Guadalupe flicker. Both birds became extinct shortly afterwards; several other taxa were found to be already gone in 1906. Thayer and Outram Bangs wrote an article in The Condor to draw attention to the situation.

In 1913 Thayer and other Harvard graduates sponsored an expedition to Alaska and Siberia, with Joseph S. Dixon and Winthrop Sprague Brooks as zoological collectors. A gull collected by Brooks on this trip was named Larus thayeri in Thayer's honour.

Thayer became ill in 1928, and donated his collection of 28,000 skins and 15,000 eggs and nests to Harvard. These included the first clutches ever collected of spoon-billed sandpiper and surfbird. After Thayer's death Harvard received his collection of 3,500 mounted birds.