It was by sheer blundering that he chanced upon the shrewdly hidden ptarmigan nest.

He fell into it.

He had essayed to walk along the trunk of a fallen pine.

The rotten bark gave way under his feet, and with a despairing yelp he pitched down the rounded crescent, smashed through the leafage and stalks of a small bush, and in the heart of the bush, on the ground, fetched up in the midst of seven ptarmigan chicks.
They made noises, and at first he was frightened at them.

Then he perceived that they were very little, and he became bolder.