GREAT BLUE HERONS. Ardea herodias Linnaeus¹⁸

Field characters.—Tallest bird occurring regularly in the Yosemite region (stands 3 feet high or more); general form slender; neck and legs very long. General color slaty blue; head marked with white and black; neck brownish; pattern of under surface streaked black and white. Flight direct, with slow, regular flapping of the broad wings; neck crooked in flight (not held out straight, as with cranes and geese); legs held out behind, extending beyond end of tail in line with body. Forages singly or in pairs. Voice: A deep guttural squawk, not often uttered.

Occurrence.—Resident in the western lowlands; may occur almost anywhere else in the region during the summer season; most frequently noted along Merced River, between Snelling and Yosemite Valley and along Tuolumne River near Lagrange; has been observed at Merced Lake, Glen Aulin, and Tuolumne Meadows. Found chiefly along streams or about lake borders, but sometimes also in fields and meadows.

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¹⁸Two races of this species occur in the Yosemite region, a darker form, the California Great Blue Heron (Ardea herodias hyperonca Oberholser), which ranges from the plains of the San Joaquin eastward at least to Yosemite; and a paler Great Basin form, the Pallid Great Blue Heron (Ardea herodias treganzai Court), which is found about Mono Lake and strays westward at least to Tuolumne Meadows. These two forms cannot be distinguished except as specimens in hand.

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In the mountainous parts of the Yosemite region the Great Blue Heron is only an irregular visitant, but at lower altitudes, in appropriate parts of the San Joaquin Valley and adjacent foothills, it is a fairly common resident. Along the river in the Merced Cañon between Merced Falls and the Yosemite Valley one or more individual birds may usually be seen, at close range, from the windows of the passing train. Single birds are occasionally observed in Yosemite Valley and, more rarely, about bodies of water in the higher country to the eastward.

The Great Blue Heron is a marsh and stream-side bird; its whole bodily make-up is adapted to gaining a livelihood in these situations and in a special manner associated with the conditions therein. Its long legs easily allow it to wade in water of considerable depth, and its long sharp bill and long neck enable it to capture fishes and other aquatic animals from a vantage point some distance above the surface. The species is also, however, an efficient catcher of terrestrial rodents. Not infrequently a bird may be seen standing motionless in an alfalfa field on the watch for pocket gophers. Although known locally by the name of "Blue Crane," this bird is a true heron, with habits not at all like those of the real cranes.

Although accustomed to civilization to the extent that it will frequently allow railroad trains to pass close by without being disturbed from its perch on rock or snag, the Great Blue Heron has not learned to avoid overhead wires; from time to time a bird is found dead or injured under telegraph lines against which it has flown. In the plains country where the birds are able to see long distances they lay their courses from place to place at once in a direct line; but in the high mountains the surrounding cañon walls force them to adopt another procedure. When they rise from the shore of a mountain lake they begin to circle upward and continue spiraling until they reach a height which will give an uninterrupted view of the surrounding elevated country; then they make off in a straight line in the desired direction. The deliberate flapping of the broad wings gives the observer the impression that the Great Blue Heron is a very slow flier. And it is, at times; individual birds have been seen by us to keep barely ahead of the train traveling about 20 miles per hour along the Merced.

Near Snelling the Great Blue Heron builds its bulky stick nests in the tall cottonwoods along the river. The belief is held locally that once the birds select and use a tree for this purpose the tree immediately dies. It is probably true, however, that the birds choose the oldest trees in the vicinity, such as are likely soon to die anyway. In the Yosemite Valley and higher country these birds are reputed to be very destructive to trout. The one bird obtained on Tuolumne Meadows, probably a straggler from the vicinity of Mono Lake, had only mammal hair and parts of a crustacean in its stomach.