MOLOTHRUS. 



MOLYBDENUM. 



178 



Female : Sooty-brown above, pale beneath. 

 Young : Like the female, with the breast spotted. 

 ThU species i a native of America, and leads a wandering life, 

 appearing in the middle and northern States of the Union at the end 

 of March or the beginning of April. The winter is ]ased in the southern 

 State* and warmer parts of the continent, where they are to be seen 

 with the Red-Wings (letma Pkcenictui) and the common Blackbirds 

 (Quucalut rertirolor) in the ploughed fields, according to Nuttall. 

 They attend on the cattle constantly, like many of the Stunixlir, 

 intent on picking up the insects which are disturbed by the qua- 

 druped* or haunt their droppings, nor do they in the colder weather 

 refuse to hunt for aquatic insects and small molluscs on the margins 

 of ponds, where, according to the author last quoted, they may be seen 

 in the winter season industriously turning over the leaves of water- 

 plants to glean such as may there adhere. But though they with 

 their associates are occasionally found in the rice and corn fields, it 

 seems that their depredations are not co-equal with those of their 

 companions, for the food of the Cow-Bunting appears to consist chiefly 

 of insects and such food as makes them for the most part independent 

 of the farmer. 



The most curious of its habits remain to be told ; for this vagabond 

 bird, like our cuckoo, never prepares a nest for itself, but drops its 

 egg in another's nest. As a concomitant to this ordinance they do 

 not pair, but polygamy prevails among the flock without exciting any 

 great jealowy ; though now and then there may be a battle, as is usual 

 in such cases, in which the strongest generally prevails. The egg, 

 which is nearly oval, varies in colour ; sometimes the ground-colour 

 is white tinged with green and sprinkled with spots of brown, and 

 sometimes pure white with nearly black spots. It is a very little larger 

 than that of the Blue-Bird. This supposititious egg is, it appears, 

 always hatched before the legitimate ones. Were this not the course 

 of nature, the species would probably perish ; for the legitimate nest- 

 lings would suffocate the newly-hatched foundling, as the latter actually 

 does suffocate the young of its foster-mother, when they afterwards 

 come into existence. 



The favourite nests appear to be those of the Red-Eyed and White- 

 Eyed Flycatchers, and the Maryland Yellow-Throat; those of the 

 Blue-Bird, the Indigo-Bird, the Chipping-Sparrow, the Song-Sparrow, 

 the Blue-Eyed Yellow Warbler, the Blue-Gray Flycatcher, the Golden- 

 Crowned Thrush, and Wilson's Thrush, are however also selected as 

 places of deposit From the various and interesting accounts of this 

 curious phenomenon we select that of Nuttall, whose personal 

 observations we proceed to lay before the reader : 



"When the female is disposed to lay, she appears restless and 

 dejected, and separates from the unregarding flock. Stealing through 

 woods and thickets, she pries into the bushes and brambles for the 

 nest that suits her, into which she darts in the absence of its owner, 

 and in a few minutes is seen to rise on the wing, cheerful and relieved 

 from the anxiety that oppressed her, and proceeds back to the flock 

 she bad so reluctantly forsaken. If the egg be deposited in the nest 

 alone, it is uniformly forsaken ; but if the nursing parent have any of 

 her own, she immediately begins to sit. The Red-Eyed Flycatcher, in 

 whose beautiful basket-like nests I have observed these eggs, proves 

 a very affectionate and assiduous nurse to the uncouth foundling. lu 

 one of these I found an egg of each bird, and the hen already Hitting. 

 I took her own egg, and left the strange one; she soon returned, and, 

 as if sensible of what had happened, looked with steadfast attention, 

 and shifted the egg about; then sat upon it, but soon moved off; 

 again renewed her observation ; and it was a considerable time before 

 she seemed willing to take her seat, but at length I left her on the 

 nest. Two or three days after, I found that she hod relinquished her 

 attention to the strange egg, and forsaken the premises. Another of 

 these birds however forsook the nest on taking out the Cow-Bird's 

 egg, although she had still two of her own left. The unly example 

 perhaps to the contrary of deserting the nest when solely occupied by 

 the stray egg is in the Blue-Bird [Bi.uF.-Biitn], who, attached strongly 

 to the breeding-place*, in which it often continues for several years, 

 has been known to lay, though with apparent reluctance, after the 

 deposition of the Cow-Bird's egg. My friend Mr. C. Pickering found 

 two nects of the Blue-Eyed Yellow Warbler, in which had been depo- 

 sited an egg of a Cow- Bird previously to any of their own ; and, unable 

 to eject it, they had buried it in the bottom of the nest, and built 

 over it an additional story. I also saw, in the summer of 1830, a 

 similar circumstance with the same bird, in which the Cow-Bird's egg, 

 though incarcerated, was still visible on the upper edge, but could 

 never have been hatched. At times, I think it probable that they lay 

 in the nesU of larger birds, who throw out the egg, or that they drop 

 their eggs on the ground without obtaining a deposit, as I have found 

 an egg of this kind thus exposed and broken. I have also remarked 

 sometimrs two of these eggs in the same nest, but in this cose one of 

 them commonly proves abortive." The same author in 1 831 saw a 

 ben Red-Eyed Flycatcher sitting on two eggs, and one of the Cow/ 

 Bird ; and he adds that this species, Virto olivacevt, and (more lately) 

 rirntylra oltraeta of Bonaparte, Mtucicapa oliracta, Linn., appears 

 to be its most usual nurse. He has known this Vino begin her incu- 

 bation with only an egg of each kind, whilst in other nests he has 

 observed as many as three belonging to the 1'i'reo, as well as that of 

 the intruder; and he suggeete that, from the largeness of the egg, the 



nest probably immediately feels full to the incubating bird, so as to 

 induce her to ait directly, when the larger egg, being brought nearer 

 to the body of the nurse than her own, is first hatched, generally, as 

 he believes, on the twelfth or thirteenth day. The legitimate eggs 

 are hatched about a day later, are often stifled by the superior size 

 of the stranger, which is affectionately nursed by the poor dupe of a 

 dam, and when the young are dead are conveyed to a distance by the 

 parent and dropped ; but they are never found immediately below the 

 nest, as would be the case if they were ejected by the young Cow-IUnl, 

 as is done by the young Cuckoo. [CucCLiDJC.] " Indeed, ' continues 

 Mr. Nuttall, " as far as I have had opportunity of observing, the 

 foundling shows no hostility to the natural brood of his nurses, but 

 he nearly absorbs their whole attention, and early displays his charac- 

 teristic cunning and self-possession. When fully fledged they quickly 

 desert their foster-parent, and skulk about in the woods, until at 

 length they instinctively join company with those of the same feather, 

 and now becoming more bold, are seen in parties of five or cix in the 

 fields and lanes gleaning their accustomed subsistence. They still 

 however appear shy and watchful, and seem too selfish to study any- 

 thing more than their own security and advantage." TheCow-liird 

 is but a poor songster. Its flitting migrations are generally made in 

 the night or in the gray of the morning. 



Besides the localities noted above, this species is also found in Mexico, 

 but according to Audubon it is rare and a visitor only in Louisiana. 

 Prince Bonaparte, in his ' Geographical and Comparative List,' gives 

 " America generally " as its locality. 



Mr. Darwin (' Journal and Remarks ') states that another species 

 (Le Troupiale Commun of Azara), of a purplish black-colour, with a 

 metallic lustre, feeds on the plain near Maldonado in large flock*, 

 mingled with other birds. Several, he says, may often be seen 

 standing on the back of a cow or horse. While perched on a hedge, 

 and pluming themselves in the sun, they sometimes attempt to sing, 

 or rather to hiss : " the noise is very peculiar ; it resembles that of 

 bubbles of air passing rapidly from a small orifice under water, so as 

 to produce an acute sound." Azara states that this bird, like the 

 cuckoo, deposits its eggs in other birds' nests. " I was several times 

 told by the country people that there was some bird with this habit ; 

 and my assistant in collecting, who is a very accurate person, found 

 a nest of the sparrow of the country (a Zunotrichia) with one egg in 

 it larger than the others, and of a different colour and shape." 

 egg is now in the museum of the Zoological Society of London. 



MOLVA. [LOTJL] 



MOLYBDE'NUM, a Metal discovered by Scheele in 1778, in a 

 mineral which resembles and had been confounded with plumbago : ho 

 gave it the Greek name of MoAi/^Saim. This mineral is composed of 

 sulphur and molybdenum ; and it has also been met with in other 

 states of combination presently to be mentioned. This substance was 

 however first reduced to its metallic state by Hjelm, another Swedish 

 chemist, and its properties have been since particularly examined by 

 Bucholz and Berzelius. 



The metal is obtained from the native sulphuret by reducing it to 

 fine powder and beating it in aqua regia ; by this the sulphur is con- 

 verted into sulphuric acid, and the metal into molybdic acid, which 

 remains in the state of a white powder after being heated to expel 

 the sulphuric acid ; when this is very strongly heated with charcoal, 

 it is reduced to the metallic state ; or the metal may be procured by 

 pasting hydrogen gas at a high temperature over the acid in a porcelain 

 tube. This metal is obtained as a porous mass or in globules, and has 

 not yet been procured in the state of a button or bar. The grains are 

 somewhat crystalline; sometimes they are of a silver-white-colour. 

 When obtained by the reduction of the oxide, this metal has not much 

 lustre, but acquires it by burnishing. Its density is 8-0. When long 

 exposed to the air at ordinary temperatures, it appears to tarnish, but 

 the oxidation is superficial. By exposure to air and heat, it is 

 first converted into brown oxide, afterwords it becomes blue, and 

 eventually molybdic acid, which is white. This oxidation does not 

 however take place completely, but only at the surface. Sometimes 

 the metal takes fire at the moment of oxidation. It does not decompose 



w.lt' T. 



Ores of Molybdenum. Oxide of molybdenum occurs encrusting the 

 sulphuret of molybdenum, and also between its lamina) in thin layers. 

 Ita structure is thin fibrous, earthy, friable, and pulverulent. Colour 

 pale-yellow or greenish. 



It has been found only in small quantity in Scotland, Norway, and 

 North America. Its composition has not been ascertained. 



Molybdic Acid or Molybdic Ochre occurs in nature in combination 

 with lead and silver. 



Sulphuret of Molybdenum, Molybdenite, is the most common 

 mineral of this metal. Occurs crystallised and massive. Primary 

 form a rhomboid. Crystallises in hexagonal crystals. Cleavage very 

 distinct, perpendicular to the axis. Fracture indistinct Hardness, 

 scratches talc, is scratched by calcareous spar. Colour lead-gray, and 

 streak the same. Flexible in thin laminae, but not elastic. Lustre 

 metallic. Opaque. Specific gravity 4'.V.)1. Rubbed on paper, it 

 leaves a gray metallic mark, and on porcelain a greenish one. Massive 

 variety amorphous; structure foliated, granular. When heated by 

 the blow-pipe on charcoal, emits a sulphurous vapour, and leaves a 

 powdery residue. It occurs in various parts of the world in England, 



