120 John Ikichman. 



this kind of food. These are the Swallows {Hirundo)^ 

 the Night Hawk and the Whippoorwill (C'ap/'z'mw^- 

 gu>i), the fly-catchers and warblers. To them, migra- 

 tion is essential to the support of life. Insects at that 

 season disappear ; the eartli is bound in frost, or 

 covered over with snow ; but long ere that, these 

 lively tenants of the air, liave obeyed the impulses 

 of a mysterious instinct, cWid liave migrated to more 

 congenial climes. 



To these, we may add all birds that obtain suste- 

 nance from fresh water ponds and rivers. These, find- 

 ing the Northern swamps, brooks and shores, frozen 

 over, migrate to milder regions, where they can pro- 

 cure suitable food. Those that gain a subsistence 

 from the sea, are not obliged to migrate, as the 

 Gulls, Petrels and Pufhns, etc. In addition to their 

 warm coverhig, they are supplied with sacs, con- 

 taining an oleagenous substance, with which they 

 lubricate their feathers, thus rendering them im- 

 pervious to moisture. While floating on the surface 

 of the water, they often draw up their feet beneath 

 their warm covering of down, and thus every part 

 of their body is protected from tlie influence of the 

 cold. 



There is anotlier circumstance that ought to be 

 taken into consideration, with regard to the capacity 

 of birds to endure cold. A large mass of air pene- 

 trates the lungs and all the aerial sacs and canals of 

 the bird, thus increasing the action of the heart and 

 propelling the tide of circulation with great rapidity. 

 The pulsation can scarcely be counted, and the tem- 

 perature of tlie bodies is as high as 106° Fahrenheit — 

 the heat of the body enables them to bear with ease, 

 the rigorous cold in the distant north, and in the 

 elevated regions of the air. * * j ^r^ye ^qq^^ 

 wild pigeons in immense flocks in Canada, in the 

 coldest winters, when the thermometer was below 



