184 HIRUNDINID.E. 



some atmospheric change, anil, at such times, fly about with 

 tumultuous and passionate eagerness, repeating their pecu- 

 liar note. It appears probable that all the swallow tribe 

 pair for life, as we may judge by their returning annually 

 to the nest of former years, but the Swifts seem peculiarly 

 attached to one another and are constantly seen to fly 

 in couples. They are very irregular in their appearance, 

 being some years seen in considerable numbers, and 

 again become so scarce in the same locality, that hardly 

 two pairs are seen together on the wing. More or less fa- 

 vourable seasons are probably the cause of these variations, 

 especially, as before said, considering their great susceptibility 

 of every atmospheric change. The entire length of the 

 Swift is eight inches six lines, the wing from the carpus 

 to the tip eight inches ; the expanse from wing to wing, 

 fifteen. The beak, from the tip to the gape, seven-eighths 

 of an inch, and six-eighths from corner to corner of the 

 mouth. Feet of four toes, all directed forward, the in- 

 nermost, which is the smallest, reversible ; the claws ivory- 

 black, strong, and very sharp, the two middle ones three 

 lines and a quarter in length. Tarsi very strong, seven 

 lines in length, feathered on the upper surface, bare 

 beneath, with a whitish-mealy skin ; toes covered with a 

 blackish skin, and two or three soft scales near the claws. 

 The second quill-feather the largest, the first a little longer 

 than the third ; the chin pearl-white, marked down the 

 centre of the feathers with dusky ; the rest of the upper 

 and under plumage, including the tail and tail-coverts sooty- 

 brown, with brilliant reflections of pale yellow, green, and 

 purple ; wings and wing-coverts sepia, tinged with purple ; 

 tail forked. 



