176 



SCIENCE. 



[N. S. Vol. V. No. 109. 



polar bird, reacliing a latitude attained by 

 few other species, and specimens taken out- 

 side the Arctic circle (at Sb. Michael's, Kam- 

 chatka, the Fteroe Islands, Heligoland, and 

 Yorkshire, England) can only be regarded 

 as stragglers. No one has yet been able 

 to explain what becomes of the thousands 

 which pass Point Barrow in the autumn, 

 and less is known of the Vinter home of 

 this gull than of the region where it breeds. 

 Murdoch supposed that its breeding grounds 

 were somewhere north of Wrangel Island. 

 Nansen's observations seem to indicate that 

 they are much farther to the west, but, as 

 Schalow remarks, "when will man's foot 

 again tread the dreary wastes of those high 

 latitudes where one of the greatest rarities 

 of northern oology is to be found ? " 



T. S. Palmer. 



WASHINGTOisr, D. C. 

 ORIGIN OF PARASITISM IN THE COWBIRD. 



Eeproductive parasitism, as we find it in 

 our Cowbirds, is such a rare exception to 

 the rule among higher animals, where pa- 

 rental affection is highly developed, that it 

 never ceases to be an object of speculation 

 as to its origin. 



There are two peculiarities for which our 

 Cowbird is renowned : The one which gives 

 him his scientific name, Molothrus, a para- 

 site ; the other, which causes him to be 

 called Cowbird, his strong attachment to 

 grazing animals, especially horses and 

 cattle. 



Now, should there not be a connection 

 between these two traits ? Nobody would 

 think that the habit of following horses 

 and cattle has been formed since the intro- 

 duction of these animals by the white man. 

 Its Indian name, ' Buffalo-bird,' was cer- 

 tainly no misnomer, and it can hardly be 

 questioned that for ages the buffalo, or 

 American bison, was the animal which, in 

 the economy of our cowbird, plaj'ed the 

 part now taken by the domestic animals. 



The distribution of the one coincides in the 

 main with that of the other, except that in 

 recent years the Cowbird has extended its 

 range to follow domesticated cattle. A few 

 years ago the bison roamed over the greater 

 part of eastern North America from the 

 Atlantic to the Rocky Mountains, in suit- 

 able places, and it was not until the last 

 century that it became exterminated in the 

 territory east of the Mississippi river. 



But the habits of the Cowbird were prob- 

 ably formed before the bison and the Red 

 Man were on the scene, since some species 

 in southern South America have similar 

 traits. 



The Cowbirds, like all other Icteridifi, 

 have their origin in South America, and of 

 the twelve species and subspecies known 

 only three enter the United States. Not 

 all the species are parasitic ; of some we do 

 not know the mode of reproduction, but 

 Molothrus badius, of Argentina, Paraguay 

 and Bolivia, builds its nest and rears its 

 young like other birds, and there was un- 

 doubtedly a time when Molothrus ater did 

 the same. 



"VVe know that fossil remains of horses, 

 not much unlike ours, are found abundantly 

 in the deposits of the most recent geological 

 age in many parts of America from Alaska 

 to Patagonia. It was probablj' at that 

 period that the Cowbirds acquired the habit 

 of accompanying the grazing herds, which 

 were wandering continually in search of 

 good pasture, water and shelter, and in 

 their seasonal migrations and movements 

 to escape their enemies. 



As the pastoral habit of the bird became 

 stronger, it gave rise to the parasitic habit, 

 simply because, in following the roving ani- 

 mals, the birds often strayed from home too 

 far to reach their nests in time for the dep- 

 osition of the egg, and, being hard pressed, 

 had to look about for another bird's nest 

 wherein to laj' the egg. 



After the acquisition of the roving habit, 



