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272 "December 22nd.—To-day, I saw a number of rooks blackening a heap of straw by a stack, whilst some were on the stack itself. Many were sitting in some elms near about, but they did not appear to me to be acting the part of sentinels. When I tried to get up to the hedge in order to watch the rooks at the stack, through it, they flew off, a good deal later than their friends in the trees must have seen me, and not till I was quite near. If these had really been sentinels, they should have warned the rest, either the instant they saw me, or at any rate, when I was obviously approaching, but this they did not do. They were, therefore, either not sentinels or inefficient ones." The second case, however, is more conclusive.

"January 8th.—To-day, on my way down to the roosting-place, I pass a number of rooks feeding in a field, and not far from the road. They are all more or less together, there are no outposts, though of course there is, of necessity, an outer edge to the flock. But neither on the hedge or in any of the trees near, are there any birds to be seen. On the other side of the field, however, and a very considerable way off, a few are sitting in some trees. It hardly seems possible that these can act the part of sentinels at such a distance, and even if they were much nearer, the feeding rooks would have either to be looking at them, to see when they flew, or else, the alarm must be given by a very loud warning note. Bearing this in mind, I alight from my cycle, and walk along the road. The rooks, without any dependence on sentinels far or near, note the fact, bear a wary eye, but continue feeding. I then stop—always an alarming measure with birds. The feeding rooks fly off to a safer distance, the ones