ofAnimah to secure Warmth. 5J.3 



and even twenty. It will follow, of course, that, in order to 

 hatch so large a number, these little birds require all their 

 animal heat to be concentrated and preserved from being dis- 

 sipated. The dipper, indeed, lays but five or six eggs, and 

 weighs from six to eight times more than any of our other 

 dome-builders ; but it is to be recollected that its being a water 

 bird, and building near water, it may have more occasion to 

 use ' all appliances ' to concentrate its heat. Such are some 

 of the circumstances which occur to me corroborative of the 

 opinion. 



On the other hand, it may be alleged, that there are more 

 birds in tropical countries which cover their nests with domes, 

 than among our European natives*. I would account for 

 this, however, on the principle of procuring shade, in the same 

 way as our sailors put up an awning on deck in tropical lati- 

 tudes ; for birds, constantly sitting on their eggs during incu- 

 bation, must in these countries be frequently exposed to the 

 rays of a vertical sun, which could scarcely fail to prove in- 

 jurious. I am well aware that it is the received opinion, these 

 covered nests are designed to protect the eggs and young from 

 snakes ; but this mistaken notion has been adopted, without 

 taking into account the natural habits of the accused snakes 

 the smaller ones of which would more readily pry into a nest 

 with a narrow hole for a side entrance, than into an uncovered 

 nest. In the instance of a domed nest of the hay-bird (Sylvia 

 trochilus'), with which I was acquainted last summer, 1 found 

 a large snake (Coluber natrix) lying close by it, and the eggs 

 untouched ; but as it had just swallowed a large frog, which it 

 disgorged upon being caught, it might, probably, have no ap- 

 petite at this time for the hay-bird's eggs. 



The same anxiety to secure warmth by preventing the dissi- 

 pation of animal heat evidently actuates the wild animals 

 which pass the winter where snow is either permanent or par- 

 tial. Some of these, such as the marmot (Ardomys Mar- 

 mota, A. Bobacy &c.), lie several weeks or months torpid in 

 cells, previously prepared with no little care. This prepara- 

 tion of a winter abode has always excited admiration ; and 



* Prince Maximilian's Travels in Brazil, p. 105 



