4 Bulletin American Museum of Natural History. [Vol. XXXVI,^ 



This knowledge is not within our reach until we have a much larger num- 

 "ber of specimens than our museums now contain. These must be collected, 

 not at widely separated localities, but at as many stations as are necessary 

 to represent the principal physiographic and climatic areas contained in 

 the range of the species. 



Our expeditions were instructed to make as complete a collection of the 

 birds at each station as circumstances permitted. The commoner, more 

 widely distributed species are more apt to reflect environmental influences 

 than rarer ones of limited distribution, and are often, therefore, of more 

 scientific value. 



One unfamiliar with the problems involved might imagine that we have 

 accumulated an unnecessarily large number of specimens."^ But I regard 

 each specimen as standing for a concrete fact. It places beyond dispute 

 the occurrence of its species at a definite place on a certain date. The con- 

 dition of its sexual organs helps to determine the relation between season 

 and period of reproduction; its external characters enable us to distinguish 

 between individual variations of sex, age and season, and those which 

 result from environment and mark the nascent species. 



The bird-life of Colombia is probably as well known as that of any 

 other part of tropical America of similar extent, but one has only to read 

 the 'Review of Colombian Ornithology,' presented beyond, to realize how 

 wholly inadequate for the ends in view, were the existing data in regard 

 to the distribution of birds in Colombia when we began our work there. 



To determine the boundaries of zones and faunas as they are manifested 

 by birds and mammals is our first aim, and in the course of this work we 

 trust that our study of purely local conditions will at times so closely connect 

 cause and effect, that we may throw some light on the laws governing 



1 Lest we be accused of needless sacrifice of life, it will be well to state that our collections are far 

 from sufficient satisfactorily to settle all the questions of speciation and distribution raised by our 

 studies. ' 



From the standpoint of bird protection, the number of specimens taken has produced about as 

 much effect on Colombian bird-life as would the collecting of the same number of plants have on the 

 Golombian flora. The results of general collecting on the avifauna of a region as a whole are always 

 negligible. It is only when the collector's attention is focused on a certain species that its niunbers 

 are appreciably diminished. A milliner's agent, for example, whom I met in Mendoza, Argentina, 

 told me that he, alone, had sent the wing and tail-quills of 16,000 Condors to ParisI All were killed 

 in the Argentine Andes where, in consequence, the species has become comparatively rare. 



On the other hand, eighty years of general collecting for millinery purposes in the Bogot& region 

 has not, so far as we could observe, seriously affected the numbers of birds inhabiting it. Our expedi- 

 tion No. 7, in passing from the Magdalena Valley over the Eastern Andes to Villavicencio, and hence 

 through the heart of the Bogota region, secured over five hundred species of land-birds in some two 

 months' collecting, a number which clearly indicates the richness of the avifauna. Nevertheless from 

 this region, as stated above, hundreds of thousands, perhaps even millions, of birds have been shipped 

 to European dealers.- 



In view of these facts, it is hardly necessary to add that our average of twelve specimens per 

 species has not perceptibly reduced the bird-life of the wide area over which we worked I 



