Carrtker : List of the Birds of Costa Rica. 331 



in almost all of the families, but they seem to be commoner among the 

 ant-thrushes, tree-creepers, and humming-birds. 



With the destruction of the tropical forests, many of the most inter- 

 esting and by far the larger percentage of the typically tropical forms 

 of bird-life are in danger of extermination. Those highly specialized 

 forms, found only in the cool dark depths of the forest cannot possibly 

 adapt themselves to the condition of affairs brought about by the re- 

 moval of the virgin forest and their doom is certain. There is no im- 

 mediate danger of such a fate, but it will ultimately come, and unless 

 thorough work is soon done in some regions, many rare and interest- 

 ing species will disappear, leaving very little knowledge of their life- 

 history and habits. 



Habits, Food, and Song as Factors in Nomenclature. 



In some respects it is unfortunate that some of the men who have 

 done the most work in the systematic arrangement of the birds, have 

 had so little experience in the field, and know so little about the habi- 

 tat, actions, and song of the many tropical forms which have always 

 proposed vexing problems to the systematise It seems to me that 

 too much importance has been attached to some slight differences in 

 physical structure and that some characters have been used for sepa- 

 rating the higher groups which are subject to much variation in appar- 

 ently closely related forms. 



Naturally a bird must be placed somewhere in the great system of 

 classification which has been built up by scientists, and characters 

 more or less arbitrary must often be used for the separation into groups 

 of such a great variety of forms. It is a well-known fact that in all 

 divisions of the animal kingdom we have instances of the trend of 

 widely separated forms toward a common point, so that two birds, 

 really not at all closely related, may have a striking superficial resem- 

 blance. These resemblances, coupled with a scant knowledge of the 

 internal anatomy of the bird and little or nothing of its habits in life, 

 have brought about many errors in the determination of the true status 

 of many species. With the hope of shedding some light on the posi- 

 tion of some Costa Rican species, I here give in detail my observations 

 on the habits of a few of these birds. 



Rhodinocichla rosea eximia. This species is to be found exclusively 

 in the thick second-growth so common about Boruca and Buenos 

 Aires, seeking the most impenetrable parts, where it spends much of 



