in the trees remain there as silent as ever, nor is there any special note uttered by any one bird of the flock, nor anything else whatever to suggest that any particular bird or birds is acting the part of sentinel." There is certainly no sentinel in this case, and in matters directly affecting their safety one might suppose that rooks, as well as other birds and beasts, would act in a uniform manner. This, however, we can clearly see, that when there happen to be trees, near where they are feeding, some of them will usually, and quite naturally, be perched in them, and average human observation and inference may have done the rest.
Rooks, I am inclined to think, are not birds that give their conscience into keeping. Each one of them is his own sentinel.
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