Reprinted with permission from the Mount Diablo Audubon Society's newsletter, The Quail.

Written by Ellis Myers

A small plain sparrow that inhabits Texas and New Mexico and whose territorial skylarking flights are dramatic. A common small bird of the western forests, known for its constant singing. A small, dark seabird of Pacific shores from Alaska to Mexico. A large, noisy flycatcher of southwestern United States and Mexico.  A finch of the western mountains. These five species of western America were named for John Cassin, although it is almost certain that Cassin never saw any of these birds living in its natural habitat.

Cassin’s Sparrow was named by Samuel Woodhouse from a specimen he collected near San Antonio during the 1851 US Army Corps of Engineers expedition from Texas to San Diego. Cassin’s Vireo was named by John Xántus. Cassin’s Auklet was described and named by William Gambel. Cassin’s Kingbird was named by George Lawrence—Lawrence’s Goldfinch was named by Cassin; Cassin’s Finch was named by Spencer Baird. John Cassin was another of the early naturalists that made Philadelphia and the Academy of Natural Sciences preeminent.

Born in 1813 to a Quaker family, his interest in natural science was, well, natural. He excelled in science studies at the Quaker boarding school in Westtown, Pennsylvania, where Thomas Say and John Townsend also studied. One of Cassin’s botany schoolbooks contains notes showing that he was finding plant species not listed in the book and making his own descriptions.

He was made honorary curator of the Philadelphia Academy of Natural Sciences in 1842. Despite the “honorary” in the title he spent endless hours with the academy collections. Cassin’s science interests and knowledge was broad. There are insect species named for him as well as the five birds. The Academy bought bird skins from around the world, and soon Cassin was the most informed U.S. ornithologist of his era and the first serious taxonomist.

Though he was a talented field observer, Cassin personally collected just one bird previously unknown. In September, 1842, he shot a new vireo near Philadelphia and named it the Philadelphia Vireo. It is curious that the bird only passes through its namesake city during migration. In all, Cassin described nearly 200 new bird species from around the world, nearly all from the Academy collection. He discovered and named Brewer’s Sparrow from a specimen he chanced across while studying the Academy's collection of Clay-colored Sparrows.

He first described Heermann’s Gull and Wrentit, both of which had been collected in California by William Gambel, and named Rufouscrowned Sparrow, Acorn Woodpecker, California (Brown) Towhee, Ross’s Goose, Williamson’s Sapsucker, White-headed Woodpecker, Kauai Oo, Hutton’s Vireo, Lawrence’s Goldfinch, Sage Sparrow, and Black-throated Sparrow.

At the Smithsonian, Spencer Baird gathered new specimens from all the military and railroad explorations of the U.S. West and Mexico. Most he then sent directly to Cassin to examine and describe. John Xántus was a Hungarian exiled from his country who became an American citizen by joining the army. He was with one of the military expeditions as a nurse to surgeon William Hammond, who was one of Baird's correspondents. Xántus was later transferred to Fort Tejon, and while there he collected the first Cassin’s Vireo. Xántus also described the flycatcher he named for Hammond.

Cassin wrote several of the government scientific reports based on explorations of the western U. S. and military records from the Mexican War. He wrote many publications and articles on birds from his study of the Academy's world-wide collection. However, his plans to issue a series of books on western birds failed due to lack of subscriptions and the interruption of the Civil War. During the Civil War Cassin joined the Union Army, then served time in a military prison after being captured by the Confederates. One volume containing fifty illustrations and descriptions of western and Mexican birds did get published “as a supplement to Audubon’s Birds of America.” It is ironic that Cassin had little respect for Audubon, feeling that Audubon "is no naturalist.”

As was Townsend's, Cassin’s life was shortened by his love of birds. It is certain he knowingly suffered two decades of arsenic poisoning to further his knowledge. Arsenic in the mixture used to preserve the bird skins he would not stop handling led to his early death at the age of 55.