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NATURE 



[April 14, 1892 



In the next chapter, entitled " A Wave of Life," we 

 have a far broader subject touched upon and illustrated 

 by a mass of curious observations. The interdependence 

 and complex relations of species, so admirably portrayed 

 by Darwin, are here brought vividly before us. We are 

 told how, during a fine moist summer, when grass and 

 flowers were abundant, mice increased to an abnormal 

 extent, so that everywhere in the fields it was difficult to 

 avoid treading on them, while dozens could be shaken 

 out of every hollow thistle-stalk lying on the ground. 

 The most incongruous animals swarmed to the feast 

 which they provided. Dogs lived almost entirely on 

 them, as did the domestic fowls, assuming the habits of 

 rapacious birds. The cats all left the houses to live in 

 the fields. Tyrant-birds and cuckoos seemed to prey 

 on nothing else. Foxes, weasels, and opossums fared 

 sumptuously, and even the common armadillo turned 

 mouser with great success. Storks and short-eared owls 

 gathered to the feast, so that fifty of the latter birds could 

 often be seen at once, and they got fat and bred in the 

 middle of winter, quite out of their proper season, in con- 

 sequence. The following winter was a time of drought, 

 the grass and herbage had all been consumed or was 

 burnt up, and the mice, having no shelter, and being 

 obliged to search for food, soon fell a prey to their nume- 

 rous enemies, and were almost wholly exterminated. 

 Their vast increase, by bringing together innumerable 

 enemies, was the cause of their succeeding decrease. As 

 Mr. Hudson well remarks : — 



" Here, scene after scene in one of Nature's silent, 

 passionless tragedies opens before us, countless myriads 

 of highly-organized beings rising into existence only to 

 perish almost immediately, scarcely a hard-pressed rem- 

 nant remaining after the great reaction to continue the 

 species." 



We cannot stop to notice a tithe of the curiosities of 

 natural history with which this volume abounds, such as 

 the poisonous toad which kills horses, and the wrestler 

 frog, which gives a sudden pinch to an enemy with its 

 muscular fore-legs, and then escapes ; the huge venomous 

 man-chasing spider, a species of Lycosa, which actually 

 pursues men on foot and on horseback ; the strange 

 dread which gnats, mosquitoes, and sand-flies have of 

 dragon-flies, so that a single individual of the latter insect 

 will cause clouds of the tormentors instantly to disappear ; 

 the interesting discussion on parasite problems, and the 

 wonderful storms of dragon-flies which precede wind- 

 storms from the interior ; the new and interesting cases 

 of mimicry and of warning colours ; and the delightful 

 chapter on the crested screamer, the author's prime 

 favourite among all the denizens of the Pampas, which, 

 though possessing a body as large as that of a swan, yet 

 soars up into the air like a lark, aind in flocks of thou- 

 sands, when so high as to appear only specks in the blue 

 sky, pours forth its song in silvery sounds delightful to 

 listen to. These and many other matters of interest 

 must be studied in the book itself, since we must devote 

 the remainder of our limited space to some valuable 

 observations and discussions on certain instincts, by 

 which new light is thrown on several disputed questions. 



The chapter on " Fear in Birds " is especially interesting, 

 since the result of the author's observations is opposed to 

 the view held by Darwin and Herbert Spencer as to their 

 NO. I 172, VOL. 45] 



instinctive fear of man or birds of prey antecedent to 

 experience or parental teaching. The one thing that is 

 instinctive is the alarm caused by the warning note of 

 the parent. This produces an effect even before the 

 chick is hatched, for, in three different species belonging 

 to widely separated orders, Mr. Hudson has watched the 

 nest while a young bird was chipping its way out of the 

 egg and uttering its feeble peep, when, on hearing the 

 warning cry of the mother-bird, both sounds instantly 

 cease, aid the chick remains quiescent in the shell for a 

 long time, or till the parent's changed note shows that the 

 danger is over. Young nestling birds take their food as 

 readily from man as from their parents, till they hear the 

 warning ci-y, when they immediately close their mouths, 

 and crouch down frightened in the nest. Parasitical 

 birds which do not recognize the warning cries of their 

 foster-parents show no fear. The young parasitical 

 cow-bird takes food from man, and exhibits no fear 

 although the foster-parents are hovering close by scream- 

 ing their alarm notes. So, a young wild dove, reared 

 from the egg by domestic pigeons which, never being 

 fed, were half wild in their habits, never acquired the 

 wildness of its foster-parents, but became perfectly tame 

 and showed no more fear of a man than of a horse. He 

 had none of his own kind to learn from, and did not 

 understand either the voices or the actions of the dove- 

 cot pigeons. Mr. Hudson has also reared plovers, tina- 

 mous, coots, and many other wild birds from eggs 

 hatched by fowls, and found them all quite incapable of 

 distinguishing friend from foe, while some, such as the 

 rhea and the crested screamer, are much tamer when 

 young than domestic chickens and ducklings. 



Mr. Hudson concludes that birds learn to distinguish 

 their enemies, first from parental warnings and later by 

 personal experience, and he considers that this view is 

 confirmed by the different behaviour of birds in the pre- 

 sence of various species of the hawk tribe, the amount 

 of alarm shown being exactly proportionate to the degree 

 of danger. Some hawks never attack birds, others only 

 occasionally. The chimango kite is chiefly a carrion- 

 feeder, and its presence excites no alarm among small 

 birds. One of the harriers is so like the chimango in 

 some states of plumage that the latter is sometimes mis- 

 taken for it, and a certain amount of fear is exhibited, 

 which, however, soon passes away on discovering the real 

 nature of the intruder. Buzzards are still more feared 

 than harriers, as they are more destructive to birds, and 

 they cause a somewhat greater amount of alarm. But 

 most dangerous of all is the peregrine falcon, and, however 

 high in the air this may be, the feathered world is thrown 

 into the greatest commotion, all birds, from the smallest 

 up to species as large as duck, ibis, and curlew, rushing 

 about as if distracted. Even when the falcon has disap- 

 peared, the wave of terror excited by it subsides but 

 slowly, and the birds continue for a considerable time to 

 be wild and excited. Now, this nicely-measured alarm, 

 proportioned to the danger to be apprehended from the 

 different species, can hardly be due to inherited instinct, 

 even if this could explain the general dread of raptorial 

 birds ; and, taken in connection with the numerous other 

 facts in the habits of young birds, leads to the conclusion 

 that fear of enemies is wholly the result of education and 

 experience. 



