ARCTIC BIRDS WITH BROWN OR BLACK 

 UNDERPARTS. 



S. L. MOSLKY, l-.E.S. 



Several Arctic shore birds undergo a remarkable chansre from 

 white in winter to hazel-nut brown or black in summer. This 

 change is mostly on the under-parts. I have been conducting 

 some experiments with a view to ascertaining the reason for 

 these remarkable changes. 



The following species have the under-parts pure white in 

 winter and nut-shell or chestnut-brown in summer : — -Black- 

 tailed GodwMt, Bar-tailed Godwit, Knot, Brown Snipe, Curlew 

 .Sandpiper, Grey- and Red-necked Phalaropes. 



The following have the under-parts black in summer: — Grey 

 Plover, Golden Plover, and Dunlin. All these, except the two 

 last, are arctic birds; and they are alpine, which, climatically, is 

 the same thing. 



The well known facts concerning the colours of clothing 

 materials as regulating the loss of heat, suggested the idea 

 that in these regions of excessive cold every advantage which 

 secures an extra degree of heat during incubation will be taken 

 advantage of by Nature and propagated, and that the coloured 

 under-parts might conduct the heat from the sitting bird to the 

 eggs better than white. 



The mercury bulb of a thermometer was surrounded with 

 several thicknesses of cotton cloth and firmly grasped in the 

 palm of the hand. Care was taken that each cloth was of a 

 similar thickness and texture. 



White, I St minute mercury rose 8h\ 2nd niuuite i^ more. 

 Red, ,, ,, ,, ,, 9^% - " ~\ " 



Black, ,, ,, ,, ,, 10^°, ,, ,, 2^ ,, 



The bulb was then wrapped in cloths, as before, and held 

 against an 8-candle electric lamp, with the following results : — 



White, I St minute mercury rose 10^", 2nd minute 11 more. 



Red, ,, , 11^' 10 .. 



Black, ,, , 14 V 12 ,, 



ll will thus be seen that the red shows a dislincl achanlage 

 o\er the white, and the black over the icd in the transmission 



Nacuralist, 



