Page:Popular Science Monthly Volume 77.djvu/129

Rh isolated facts, and too often falls into temptation by trying to interpret them without a full knowledge of their history. The act in question may appear irretrievably stupid or exceptionally intelligent, while upon fuller knowledge, either view might prove wholly erroneous. Illustrations could be multiplied, but the few which follow, may be of interest.

Shrike Impaling Prey.—The great northern shrike is well known to impale its prey, such as grasshoppers, small birds and rodents, on thorns, and it presumably returns to them when in need of food, although I am not aware that the bird has ever been actually seen in the act of reclaiming its booty. According to some accounts the shrike impales its prey in order to rend it with the greater ease, but still goes on killing after it has satisfied its appetite.

On April 8 of last year I happened to witness a futile attempt at impalement under such favorable conditions of seeing all that transpired, that any mistake as to the meaning of the actions would seem to be impossible. A harsh piercing cry attracted my attention to the bird, which almost at the same moment dived into the stubble of an adjoining field, and came up with a large object in its bill. Fortunately it flew directly towards me, and alighted on the bare, lower branch of a maple tree, less than ten feet from my eye, as if completely preoccupied, and indifferent to observation. I could now see plainly that it held a little shrew, about three and a half inches long, and in a strangle grasp by the nape of the neck, for the body was as limp as a rag. The shrike at once proceeded to walk along the branch and try to impale the rodent, extending its head and drawing the body of the animal in a peculiar manner, against the soft twigs of the tree. It tried the terminal twigs, and the equally soft lateral shoots, and went through the same motions on two different branches. After several minutes of this ineffective effort, with a loud rasping call of a different character, it flew off in the direction of some woods, and was seen to descend to the ground.

The interpretation of such behavior seems obvious—that the shrike, when under the spell of a strong impulse, does not know a thorn-bush from a maple tree. Must it try tree after tree, until one of the right sort is found? If it can return to its tree by memory, why can not it find one suited to its puposespurposes [sic] by intelligence; or, was this a bird with inherited instinct to impale, but with no previous experience with thorns?

Robin "Tying Knots."—So far as I have observed, the robin in nest-building, ties no proper knots, unless the present case (Fig. 23) be exceptional, although strings are coiled more or less effectively about adjoining twigs. This nest was placed in a crotch of a pine tree, and one of its supporting branches bore the peculiar double loop or "knot" which is here shown. It seems that a piece of string over two