[Note 55] p. 227.—Crocodile Bird.
This is usually regarded as Pluvianus or Hyas ægyptius—one of the “plovers” in the wide sense. Professor Newton observes, however, in a note to the article “Plover” in his Dictionary of Birds that there is not perfect unanimity on the matter, as some have supposed that the “crocodile bird” was a lapwing—Hoplopterus spinosus. But the elder Geoffroy St. Hilaire and Brehm, who both saw the bird enter the reptile’s mouth, regarded it as Pluvianus ægyptius.
Dr. Leith Adams notes (1870) that the crocodile is now rarely seen below Beni Hassan, and is evidently receding everywhere below the second cataract. Both Herodotus and Strabo speak of its domestication, and it is tamed at the present day by certain religious sects in India. On the lower Nile it is shy and difficult even to shoot.
“A sail, or the smoke and noise of a steamboat, suffice to warn the crocodiles basking on the sand-banks, or their common companions, the black-headed and spur-winged plovers (Pluvianus ægyptius and Hoplopterus spinosus), which are frequently seen perched on their backs, and always prepared to give timely warning of approaching danger, just as the Father of History noticed them 2300 years ago, and, strange to say, his well-known story is current among the modern Egyptians, who, as usual, have put a tail to the narrative. They say, that in addition to its office of leech-catcher to the crocodile, it occasionally does happen that the zic-zac—so called from its note of alarm—in searching for the leeches, finds its way into the reptile’s mouth when the latter is basking on a sand-bank, where it lies generally with the jaws wide apart. Now this is possible and likely enough, but the captain of our boat added, that occasionally the crocodile falls asleep, when the jaws suddenly fall, and the zic-zac is shut up in the mouth, when it immediately prods the crocodile with its horny spurs, as if refreshing the memory of his reptilian majesty, who opens his jaws and sets his favourite leech-catcher at liberty” (Leith Adams).
MIGRATIONS OF MAMMALS.
[Note 56] p. 237.—Rats.
The brown rat (Mus decumanus) is much stronger than the black rat (Mus rattus), and gains an easy victory. The rivalry between the two species is one of the examples Darwin gives of his generalization that the struggle for existence is most severe between allied forms, and there seems no doubt that the brown rat has often ousted and will even devour the black rat. The latter is now rare in Britain. It should be noted, however, (1) that the two species are said sometimes to live together on board ship, (2) that cases have been recorded where the black rat returned and defeated its conquerors, and (3) that the black rat keeps more about houses, stables, and barns, is therefore more readily exterminated by man, whose efforts were doubtless increased when a second species appeared on the scene. The case is of some importance in connection with the generalization referred to above.
[Note 57] p. 240.—Migrations of Reindeer.
Of the reindeer in Spitzbergen, Nordenskiöld writes:—“During the summer it betakes itself to the grassy plains in the ice-free valleys of the island; in the late autumn it withdraws—according to the walrus-hunter’s statements—to the sea-coast, in order to eat the seaweed that is thrown up on the beach. In winter it goes back to the lichen-clad mountain heights in the interior of the country, where it appears to thrive exceedingly well, though the cold during winter must be excessively severe; for when the reindeer in spring return to the coast they are still very fat, but some weeks afterwards, when the snow has frozen on the surface, and a crust of ice makes it difficult for them to get at the mountain sides, they become so poor as to be scarcely eatable. In summer, however, they speedily eat themselves back into condition, and in autumn they are so fat that they would certainly take prizes at an exhibition of fat cattle.”
Wrangel describes migrations of thousands of reindeer in Eastern Siberia moving from the mountains to the forests, where they winter. He mentions his guide’s assertion that each body is led by a female of large size.