HEAT AND ITS INFLUENCE 213 



The heat itself may have something to do with 

 making them leave, although on the whole birds 

 from temperate countries or of mountaineering 

 habits seem to bear heat as well as tropical resi- 

 dents, judging from what I was able to observe at 

 the Calcutta Zoo. 



This is a most remarkable fact, considering that 

 the very peculiarities of birds I alluded to above as 

 fitting them to withstand cold are just those 

 which ought to make them susceptible to heat ; 

 and it is a curious fact that the warmly-clad Duck 

 tribe bear heat, even when migrants from the 

 north, particularly well, while the thinly-clothed 

 Pheasant family are more susceptible than any other 

 birds ; the Monaul bears heat worse than any bird 

 I know, panting in a temperature which provokes 

 no such manifestation of oppression from any other 

 bird. Among the Pigeons, too, I noted the Hima- 

 layan Snow-Pigeon (Columba leuconota) showed no 

 distress at the heat, although a high alpine bird, 

 while some of the warm-climate-dwelling fruit- 

 Pigeons were obviously affected, as were many 

 Parrots. Crows also feel heat much, even tropical 

 species like the Indian House-Crow, and the House- 

 Sparrow, although it lives well through both heat 

 and cold, pants constantly in the Indian summer, 

 while the imported Goldfinch seems quite indifferent 

 to heat. 



It is noteworthy, too, that while the Mallard in 

 its wild state does not visit the tropics except on 

 its southern migrations, its descendant, the domestic 



