» NEW YORK STATE MUSEUM 



snowstorm millions of longspiirs were destroyed in Minnesota (see page 

 56, volume i). 



Winds are also a climatic factor of effective influence not only in 

 determining the humidity and the rainfall of a region, but also because 

 of their influence upon migrating birds. As an example note the destruction 

 of warblers, beaten into the sea by severe head winds while crossing the 

 Gulf of Mexico, mentioned by Frazar (Henshaw, Nutt. Om. Club Bui. 6, 

 189). Every bird student may also recall numerous instances of nests and 

 young birds blown down and destroyed by high winds. 



Other climatic factors, such as hail and electricity, might also be 

 mentioned, and the illustrations given might be multiplied indefinitely, 

 but we trust that those cited will serve to show that these various factors 

 act directly upon the physiological nature of the bird and thus serve to 

 control its abundance, or even its very presence in a given locality. 



Physiographic factors. The wrinkling and sculpturing of the earth's 

 surface into great or small land masses, mountains, ravines, valleys, flood 

 plains, marshes, streams, lakes, sounds and seas, thereby determining the 

 slope of the land and the influence of the sun's rays upon it, all have great 

 influence upon the avifauna of a region. It is evident that they control 

 many of the climatic factors, especially the latitude and altitude determin- 

 ing the temperature and the humidity, and the latter is controlled also 

 by the nearness to the sea and the presence of streams or underground 

 water on the slopes of ravines and hillsides. 



The various statements made in the chapter on distribution in 

 volume I, illustrate the influence of mountains or altitude upon the various 

 zones of bird life within the State. The effect of ravines is well displayed 

 in central and western New York where many Canadian species are often 

 found on the south side of ravines which are not exposed so directly to 

 the sun's rays, whereas on the north margin of the same ravine Alleghanian 

 and Carolinian species usually predominate. The influence of streams and 

 bodies of water is clearly illustrated by their effect on the presence of such 

 species as kingfishers, herons, ducks and shore birds. Marshes are 



