Young Audubon, we may be sure, lost no time in exploring the resources of this fine estate, where every bird, tree and flower came to him as a new discovery. In following the Perkioming above the mill dam he found a cave, carved out of the rocks, as he thought, by nature's own hand, which was a favorite haunt of the unpretentious but friendly pewees, the first American birds to attract his serious attention. So delighted was the youthful naturalist that he decided to make the pewees' cave his study; thither accordingly he brought his books, pencils and paper, and there made his first studies of American bird life, in the spring of 1804, in the third year of the presidency of Thomas Jefferson. It was early in the season when Audubon chanced upon this quiet retreat; the buds were swelling and maples had already burst into bloom, but snow still lingered in patches through the woods, and the air was piercing chill. The pewees were not yet at home, but one of their nests, fashioned of mud and finest moss, was fixed above the vaulted entrance; their coming was not long delayed, and Audubon, marking the very night or day's dawn when the first pewee arrived, saw them beginning to restore their old home on the tenth of April. Strange to say, almost at that very time another pioneer in American ornithology, Alexander Wilson, who will enter this history later, was teaching a rough country school at Gray's Ferry, Kingsessing, also on the Schuylkill, and not over twenty-five miles away. Though Audubon's early studies were very desultory, both naturalists began their observations at about the same time, for on June 1, 1803, Wilson wrote to a friend that many pursuits had engaged his attention since leaving Scotland in 1794, and that then he was "about to make a collection of all our finest birds." It must be set down to Audubon's credit that in the little cave on the banks of the Perkioming, in April, 1804, he made the first "banding" experiment on the young of an American wild bird. Little could he or any one else then have thought that one hundred years later a Bird Banding Society would be formed in America to repeat his test on a much wider scale, in order to gather exact data upon the movements of individuals of all migratory species in every part of the continent. After a few trials, "I fixed," said he, "a light silver thread on the leg of each, loose enough not to hurt the part, but so fastened that no exertions of theirs could remove it." In the following spring he had the satisfaction of catching several pewees on their nests farther up the creek, and of "finding that two of them had a little ring on the leg," proving that the young of a migratory bird, steering by the "compass" which is carried in its brain, did sometimes return to its home region, if not to the actual cradle or home site.