In the early 1900s, professor G. E. Beyer of Tulane University in New Orleans collected many Upland Sandpipers (Bartramia longicauda) on the Gulf Coast as the birds passed through during their spring migration. (More than likely, he killed them with a shotgun, a standard method for collecting birds in those days.) These birds invariably had small freshwater snails of the genus Physa attached to the feathers on the undersides of their wings. Beyer wrote: “I used to count the number of snails regularly; at one time I found as many as forty-one, often between twenty and thirty, never less than ten or twelve.” He thought the sandpipers might have placed the snails in their wing feathers on purpose as a source of food, as if they were carrying provisions in a backpack.

Although Beyer couldn’t tell whether the snails were the same as the local Physa species, he noted that, at the time of year the birds were collected, the local Physa snails were not often seen—they only became abundant later in the spring. Furthermore, only sandpipers collected soon after their arrival from the south carried snails. These observations indicated that the birds were not finding the snails locally, but instead had carried them on their journey across the Gulf of Mexico, either from islands in the Caribbean or from points farther south.