The portion of the lake bottom selected for a feeding-ground lies at a depth of fifteen or twenty feet below the surface, and is covered with a short growth of algae and other aquatic plants,—­facts I had previously determined while sailing over it on a raft.  After alighting on the glassy surface, they occasionally indulged in a little play, chasing one another round about in small circles; then all three would suddenly dive together, and then come ashore and sing.

The Ouzel seldom swims more than a few yards on the surface, for, not being web-footed, he makes rather slow progress, but by means of his strong, crisp wings he swims, or rather flies, with celerity under the surface, often to considerable distances.  But it is in withstanding the force of heavy rapids that his strength of wing in this respect is most strikingly manifested.  The following may be regarded as a fair illustration of his power of sub-aquatic flight.  One stormy morning in winter when the Merced River was blue and green with unmelted snow, I observed one of my ouzels perched on a snag out in the midst of a swift-rushing rapid, singing cheerily, as if everything was just to his mind; and while I stood on the bank admiring him, he suddenly plunged into the sludgy current, leaving his song abruptly broken off.  After feeding a minute or two at the bottom, and when one would suppose that he must inevitably be swept far down-stream, he emerged just where he went down, alighted on the same snag, showered the water-beads from his feathers, and continued his unfinished song, seemingly in tranquil ease as if it had suffered no interruption.

[Illustration:  OUZEL ENTERING A WHITE CURRENT.]

The Ouzel alone of all birds dares to enter a white torrent.  And though strictly terrestrial in structure, no other is so inseparably related to water, not even the duck, or the bold ocean albatross, or the stormy-petrel.  For ducks go ashore as soon as they finish feeding in undisturbed places, and very often make long flights over land from lake to lake or field to field.  The same is true of most other aquatic birds.  But the Ouzel, born on the brink of a stream, or on a snag or boulder in the midst of it, seldom leaves it for a single moment.  For, notwithstanding he is often on the wing, he never flies overland, but whirs with, rapid, quail-like beat above the stream, tracing all its windings.  Even when the stream is quite small, say from five to ten feet wide, he seldom shortens his flight by crossing a bend, however abrupt it may be; and even when disturbed by meeting some one on the bank, he prefers to fly over one’s head, to dodging out over the ground.  When, therefore, his flight along a crooked stream is viewed endwise, it appears most strikingly wavered—­a description on the air of every curve with lightning-like rapidity.