344 IN THE WILDS OF SOUTH AMERICA 



one of them and, within a few hours, reached a habitation 

 called Bella Vista. The shambling structure stood on the 

 edge of a clearing planted in sugar-cane. Dense jungles 

 of wild cane and brush bounded the plantation. As I was 

 already convinced that the Rio Grande is the avenue up 

 which the chaco bird-life was penetrating into the higher 

 regions, we determined to remain at Bella Vista sufficiently 

 long to substantiate my views; it required only one day for 

 this purpose. The species that had been found in limited 

 numbers farther up, and that seemed to belong to a strange 

 fauna, exist in abundance at Bella Vista; among them are 

 brown-shouldered orioles, white anis (Guira), fork-tailed 

 goatsuckers, white-throated toucans (Ramphastos) and 

 many others. 



Pigeons (Leptoptila) were so numerous that they suffered 

 for lack of food. I am unable to say whether there had 

 been an abnormal increase in the number of the species, 

 or if the food-supply was unusually low; but one thing is 

 certain — they were in a very emaciated condition and some 

 of them had become so weakened that flight was impossible, 

 and they fell an easy prey to the natives or predatory ani- 

 mals. I also noticed that all the pigeons were infested with 

 parasites, but the weaker individuals were covered with 

 them, including many winged, fly-like bird-ticks (Hippo- 

 boseidce) that skipped among the feathers at bewildering 

 speed, and finally flew away with a loud buzz; sometimes 

 the repulsive insects settled on our hands or faces, when 

 it was almost impossible to displace them, owing to their 

 agile movements and to their clinging ability caused by 

 the hooks on their feet. 



This furnished a veiy good illustration of the survival 

 of the fittest, and one that I believe is typical of what 

 happens in many instances. Owing, perhaps, to unusual 

 or long-continued favorable conditions, the species had 

 become exceedingly numerous. So long as there was no 

 shortage in the food-supply, the birds were able to hold 

 their own and keep increasing; but, as the season of famine 



