\\~idmann A Preliminary Catalog of the Birds of Missouri. 153 



played the part now' taken by the domestic animals. The dis- 

 tribution 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 suitable 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 probably formed before the bison and the Red Man were on 

 the scene, since some species in southern South America have 

 similar traits. The Cowbird, like all other Icteridae, have their 

 origin in South America, and of the twelve species and sub- 

 species known, only three enter the United States. Not all the 

 species are parasitic; of some we do not know the mode of re- 

 production, but Molothrus badius of Argentine, Paraguay 

 and Bolivia builds its nest and rears its young like other birds, 

 and there was undoubtedly a time when Molothrus ater did the 

 same. 



"We know that fossil remains of horses, not much unlike ours, 

 are found abundantly in the deposits of the most recent geo- 

 logical age in many parts of America from Alaska to Patagonia. 

 It was probably at that period that the Cowbird acquired the 

 habit of accompanying the grazing herds, which were wandering 

 continually in search of good pasture, water and shelter, 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 

 animals, the bird often strayed from home too far to reach its 

 nest in time for the deposition of the egg, and, being hard, 

 pressed had to look about for another bird's nest where-in to lay 

 the egg. 



"After the acquisition of the roving habit it is not difficult to 

 imagine that such cases occurred quite often, especially when 

 with the change of climate both, birds and mammals, spread more 

 and more into the temperate regions, where the spring move- 

 ments of the grazing animals fell together with the bird's breeding 

 time. By a combination of favorable circumstances this new 

 vay of reproduction proved successful, and the parasitic off- 

 spring became more and more numerous. In the course of time 

 the art of building nests was lost, the desire to incubate entirely 

 gone, paternal and conjugal affection deadened, and parasitism 

 had become a fixed habit." 



