NATURE 



\Nov. 7, 1889 



and we feel that we should not be doing justice to Mr. 

 Hudson if we did not quote for their benefit one speci- 

 men of this naturalist's writing. He is describing the 

 habits of the Carancho {Polyborus tharus) : — 



" When several of these birds combine they are very 

 bold. A friend told me that while voyaging on the 

 Parand. River a black-necked Swan flew past him hotly 

 pursued by three Caranchos ; and I also witnessed an attack 

 by four birds on a widely different species. I was standing 

 on the bank of a stream on the Pampas watching a great 

 concourse of birds of several kinds on the opposite shore, 

 where the carcass of a horse, from which the hide had 

 been stripped, lay at the edge of the water. One or two 

 hundred Hooded Gulls and about a dozen Chimangos were 

 gathered about the carcass, and close to them a very large 

 flock of Glossy Ibises were wading about in the water, 

 while amongst these, standing motionless in the water, 

 was one solitary white Egret. Presently four Caranchos 

 appeared, two adults and two young birds in brown 

 plumage, and alighted on the ground near the carcass. 

 The young birds advanced at once and began tearing at 

 the flesh ; while the two old birds stayed where they had 

 alighted, as if disinclined to feed on half-putrid meat. 

 Presently one of them sprang into the air and made a 

 dash at the birds in the water, and instantly all the birds 

 in the place rose into the air screaming loudly, the two 

 young brown Caranchos only remaining on the ground. 

 For a few moments I was in ignorance of the meaning of 

 all this turmoil, when, suddenly, out of the confused black 

 and white cloud of birds the Egret appeared, mounting 

 vertically upwards with vigorous measured strokes. A 

 moment later, and first one, then the other, Carancho also 

 emerged from the cloud, evidently pursuing the Egret, and 

 only then the two brown birds sprang into the air and joined 

 in the chase. For some minutes I watched the four birds 

 toiling upwards with a wild zigzag flight, while the Egret, 

 still rising vertically, seemed to leave them hopelessly far 

 behind. But before long they reached and passed it, and 

 each bird as he did so would turn and rush downwards, strik- 

 ing at the Egret with his claws, and while one descended the 

 others were rising, bird following bird with the greatest 

 regularity. In this way they continued toiling upwards 

 until the egret appeared a mere white speck in the sky, 

 about which the four hateful black spots were still 

 revolving. I had watched them from the first with the 

 greatest excitement, and now began to fear that thej'^ 

 would pass from sight and leave me in ignorance of the 

 result ; but at length they began to descend, and then it 

 looked as if the Egret had lost all hope, for it was drop- 

 ping very rapidly, while the four birds were all close to it 

 striking at it every three or four seconds. The descent 

 for the last half of the distance was exceedingly rapid, 

 and the birds would have come down almost at the very 

 spot they started from, which was about forty yards from 

 where I stood, but the Egret was driven aside, and sloping 

 rapidly down struck the earth at a distance of two 

 hundred and fifty yards from the starting point. Scarcely 

 had it touched the ground before the hungry quartette 

 were tearing it with their beaks. They were all equally 

 hungry no doubt, and perhaps the old birds were even 

 hungrier than their young ; and I am quite sure that if 

 the flesh of the dead horse had not been so far advanced 

 towards putrefaction they would not have attempted the 

 conquest of the Egret. I have so frequently seen a pure 

 white bird singled out for attack in this way, that it has 

 always been a great subject of wonder to me how the two 

 common species of snow-white Herons in South America 

 are able to maintain their existence ; for their whiteness 

 exceeds that of other white waterfowl, while, compared 

 with Swans, Storks, and the Wood-ibis, they are small 

 and feeble. I am sure that if these four Caranchos had 

 ..attacked a Glossy Ibis they would have found it an easier 



conquest ; yet they singled out the egret, purely, I believe^ 

 on account of its shining while conspicuous plumage." 



In his introduction Dr. Sclater gives a resume ol the 

 number of genera and species inhabiting the Argentine 

 Republic, and shows that the avifauna of that portion of 

 South America belongs to the Patagonian sub-region. A 

 little sketch-map would have been useful, to show the 

 configuration of the country and the proportions of the 

 mountain-ranges, as it is evident that a district which can 

 boast of a Dipper, and be at the same time the home of 

 two Cariamas, must possess elements of two very different 

 avifauuce. Some day, no doubt, an exact exploration, such 

 as that now being undertaken in Mexico by Messrs. 

 Salvin and Godman, will trace the limits of the avifaunae 

 of the Pampas and the mountain regions. If Mr. Hudson 

 could only be induced to resume his work of exploration 

 and visit the interior of the Argentine RepubHc, the 

 results would be, we venture to say, of the first importance 

 to science. 



Dr. Sclater, we notice, draws his comparisons of the 

 different orders of Argentine birds from the " Nomenclator 

 Avium Neotropicalium " of 1873, which is rather ancient 

 history. The statistics of American birds must have 

 altered considerably since that date, if we may judge 

 from the Tanagers alone, which numbered 302 species in 

 1873, and in 1886 had reached 377 in number, according 

 to Dr. Sclater's own estimate. In dividing the Neotropical 

 Region into the sub-regions he adopts the conclusions of 

 Prof. Newton in the " Encyclopaedia Britannica," but the 

 names of one or two of them are changed. The bound- 

 aries seem to be extremely natural, according to our 

 present state of knowledge, though we would scarcely 

 consider the Central American sub-region (or the Trans- 

 panamic sub-region, as Dr. Sclater renames it) to be 

 bounded on the north by Tehuantepec ! The author 

 probably intended to give only a general outline, for the 

 northern boundaries of the Central American sub-region 

 are much more elaborately defined in fact. 



R. BOWDLER SHARPE. 



OUR BOOK SHELF. 



The Chemistry of the Coal-tar Colojirs. From the Ger- 

 man of Dr. R. Benedikt. Translated, with Additions, 

 by Dr. E. Knecht. Second Edition. (London : George 

 Bell and Sons, 1889.) 

 Dr. Benedikt's little book is a standard treatise in 

 Germany, where the literature of the coal-tar colours is 

 fast becoming a most important branch of the general 

 literature of applied chemistry ; and Dr. Knecht has 

 done excellent service in making the work more gener- 

 ally known to English readers by means of his transla- 

 tion. It is remarkable that, although England may be 

 said to have originated the coal-tar colour industry, she 

 has contributed comparatively little to the general hter- 

 ature of the subject. Practically, all the systematized 

 information we possess has come to us through the 

 medium of French and German manuals. A number 

 of our chemists could be named who have communicated 

 original memoirs on the constitution of organic colouring- 

 matters to the recognized organs of chemical research, 

 but their work is very special in its character, and ap- 

 peals rather to the pure chemist than to the technologist, 

 and hence is seldom read by the latter. The want of a 

 good, sound, and comprehensive treatise on the subject 



