He knows that they are incapable of paying him out, and when he finds them off their guard he will drop down and inflict a blow just for the fun of the thing.

This outraged crow appeared determined to have his revenge.
Then the storm broke on me, and so fiercely did the rain and sleet thrash me that, fearing a cold soaking, I fled before it to the rim of the plain, where the wheatear had vanished, and saw a couple of hundred yards down on the smooth steep slope a thicket of dwarf trees.

It was, the only shelter in sight, and to it I went, to discover much to my disgust that the trees were nothing but elders.

For there is no tree that affords so poor a shelter, especially on the high open downs, where the foliage is scantier than in other situations and lets in the wind and rain in full force upon you.
But the elder affects me in two ways.

I like it on account of early associations, and because the birds delight in its fruit, though they wisely refuse to build in its branches; and I dislike it because its smell is offensive to me and its berries the least pleasant of all wild fruits to my taste.