The Warblers of Central New York 



153 



about the edges of sphagnum bogs, along cool trout-streams, and in the deep 

 ravines. 



Even as strange as the association of Louisiana Water-Thrushes with nor- 

 thern Warblers in the ravines is that which occurs in the swampy woodlands 

 at the north end of Cayuga Lake. Here are the standing pools of water and the 

 acres of skunk cabbage that attract 

 large numbers of Mourning Warblers 

 and Water-Thrushes, but with them, 

 because of the open character of the 

 deciduous trees, the undergrowth and 

 the heat of the lowland woods, are 

 numbers of the Austral Cerulean and 

 Hooded Warblers. The typically Tran- 

 sition Redstarts and Yellow Warblers 

 are the most abundant forms, and with 

 them a colony of Goldenwings. Truly, 

 with some birds, humidity and the 

 resulting vegetation are more important 

 than temperature in controlling their 

 distribution. 



Temperature and humidity are ordi- 

 narily so closely interwoven that it is 

 difficult to determine which is the more 

 important. Extensive forest growth 

 always increases humidity by retarding 

 evaporation and by the actual discharge 

 of moisture from the leaves. This, in 

 turn, modifies the temperature. When 

 all of central New York was covered 

 with forest, much cooler and more 

 humid conditions undoubtedly existed 

 than do today, and the birds that are 

 now confined to the ravines and hill- 

 tops were probably much more wide- 

 spread. This might have been due to 

 temperature alone. But when, today, we 

 fmd adjacent woodlands, where tem- 

 perature conditions are approximately the same, the dry woods supporting 

 purely Transition or even Upper Austral birds, and the swampy woods 

 supporting birds that are common throughout Canadian woodlands, it seems 

 that humidity is the more important factor in controlling their distribution, and 

 that the extensive forest growth and lower temperature of the Canadian wood- 

 lands produces the necessary humidity even where there is no standing water. 



A HOME IN THE WOODS 

 A typical nest of the Kl.ick-throated Blue War- 

 bler in a beech sprout, with the female incubating 



