I recognized my particular favorite, with unerring aim. On my remonstrating with him, he said they were fig-peckers and destroyed the fruit. I laughed at him, and, to convince him that he was wrong, took out my pocket-knife and cut open one of the dead birds. It was his turn to laugh, for the maw of the bird was distended to the full with the soft, seedy fig-pulp! The green woodpecker, whose whole structure should make it a first-class insect-eater, is very fond of service-berries, and is, according to Pallas, destructive to the grapes around Astrakhan. Another woodpecker is fond of hazel nuts, and has learned how to crack them; but it may be that it was first introduced to this sort of food by exploring the nuts for worms. In fact, there is great room for the development of individual tastes in birds. But there are limitations in the matter, and the maxim "What is one man's meat is another's poison" applies well in this case. Housedoves can eat beans without harm, but geese after partaking of them sicken and sometimes die. The cause of the difference is mechanical. The doves grind up the beans in their crop, while the geese have to digest them, and are sickened or killed by the swelling they undergo in the process. A real physiological puzzle is presented, however, in the case of some chemically acting poisons which a few animals, including some birds, can partake of with impunity, while they are deadly to all other creatures.
The birds' work is not always done when they have captured their food. Sometimes they have to prepare it to a certain extent. Many of the smaller birds of prey pluck their game before eating it. Others wash their meat, as I once saw a stork do; and while this queer bird would swallow frogs without any ceremony, it gave the mice that were thrown to it a thorough soaking, probably because their hairiness interfered with the comfortable swallowing of them. A sagacious canary-bird I once knew had learned the art of soaking in its drinking-vessel the crumbs that were too hard for its bill to break up. Shell-fish give birds much trouble, but the heron proves itself a match for them by swallowing them whole, shells and all, and keeping them in its maw till the animals are killed by the pressing in of the digestive fluids, and the shells open; then it spits them up and feasts upon the soft parts. Crows carry them up into the air and drop them upon stones, whereby the shells are broken up. The 1am mergeyer, according to Krüger's observations, does the same with marrow-bones and turtles; and it is possible that the eagle that killed Thales by dropping a tortoise upon him, mistook the shiny skull of the philosopher for a big, extra hard stone!
Storing up of food is quite a common practice in the bird-world. A European species of nut-hatch collects hazel-nuts when they are abundant, and hides them in the hollows of trees; and the enow-hen of Greenland does something of the same kind. The pine nut-cracker collects vetches, and the common nut-hatch, which appears frivolous
