The persecutions to which the Crow is subjected have developed in them a wariness and a distrust that is foreign to their nature. They can only live by keeping on a constant lookout for dangers, and by learning to distinguish the weapons that threaten their destruction. As soon as anything is seen that causes alarm, the signal is at once given, and the warning passed from one to another. In New Jersey and in Pennsylvania, during the winter months, the Crows assemble in immense flocks, and their movements appear to be regulated by the guidance of a few chosen leaders. I received from the lips of the late John Cassin, an ornithologist hardly less remarkable for his outdoor observations than for his researches in the closet, only a few days before his death, a very surprising account of the movements of a large army of Crows, witnessed by himself, in the spring of 1868. On a Sunday morning in April, when Philadelphia was enveloped in a fog so dense and impenetrable that it was hardly possible to distinguish objects across its streets, Mr. Cassin’s attention was called to an immense accumulation of these birds in Independence Square. The whole park he found, to his utter astonishment, occupied by an immense army of Crows. They filled all the trees, bending down the overloaded branches, and swarmed over and covered the ground. The entire space seemed alive with Crows. They had evidently become bewildered in the fog, and had strangely taken refuge in this small park in the very heart of Philadelphia. As if aware of their close proximity to danger, the whole assembly was quiet, orderly, and silent. A few birds, evidently acting as leaders, moved noiselessly back and forth through their ranks, as if giving tacit signals. These movements were followed by the departure of a few scouts, as if sent to make explorations, but they soon returned unsuccessful. Again were repeated the uneasy movements of their leaders, passing slowly and cautiously through their close ranks. After an apparently much longer consultation, another small party ascended to explore, wheeling round and round in wider and wider zones. At length, satisfied with their observations, they quietly returned, and made their report in a manner evidently understood, though not audibly expressed; for immediately the leaders passed again among the crowd, and, as if signals were given for a general movement, the whole of this immense congregation, numbering, Mr. Cassin estimated, hundreds of thousands, rose slowly and silently, preceded by their scouts, and, moving off in a westerly direction, were soon lost to view.