CHAPTEE VII. 



ZOOLOGICAL EEGIOm. 



To write upon the Geographical distribution of the Charadriidse and to omit all mention of 

 the Zoological Regions of Sclater and others would be unpardonable ; but these Zoological 

 Regions have nothing whatever to do with the group of birds under consideration. 



In making these remarks I am only stating a fact, and not in any the least degree 

 suggesting that the importance of these Zoological Regions has been over-valued. 



No one appreciates their value more than I do, but the fact remains that they have 

 apparently not even a remote connection with the geographical distribution of the Chara- 

 driidse. These birds only recognize three Regions : — 



First, an Arctic Region, whence they originally sprung, and whither more than a quarter 

 of them still migrate every spring to breed. We may take the month of July as the height 

 of the breeding-season — a period when in these regions there is everywhere an unlimited 

 supply of food, perpetual daylight, and a mean temperature for the month varying from 

 60° in the lower latitudes to 40° in the higher ones. 



Second, a Tropical Region, where about the same number of species (rather more than 

 a fourth of the whole) breed and reside all the year round. Here also there appears to be 

 an ample if not unlimited supply of food ; but the duration of daylight is lessened by one 

 half, and the mean temperature of July, north of the equator, and of January, south of the 

 line, varies according to locality from 90° to 77°. 



The third Region has a mean temperature during the breeding-season varying from 

 77° to 60°, and may consequently be called the Temperate Region. Geographically it is 

 split into two subregions by the Tropical Region, the hmit of the north Temperate Region 

 being decided by the isothermals of July, and those of the south Temperate Region by the 

 isothermals of January. 



The boundaries of these Regions are deflected from the longitudinal parallels by 

 oceanic currents and other causes. The Gulf-stream, which raises the January isothermal 

 of 32° from the Black Sea almost to the latitude of the North Cape in the Atlantic, has 

 exactly the contrary effect in summer, depressing the July isothermal of 60° from the White 



i2 



Zoological 

 Regions of 

 the Chara- 

 driidse. 



Arctic 

 Eegion. 



Tropical 

 Region. 



Temperate 

 Eegion. 



