836 STEBNA OF FISSIROSTEES. 



rushes, either by its power of flight like the falcon, 

 or by a momentum of gravitation like the eagle. Its 

 sternum bears up the whole under-part of the body, 

 and thus it can remain longer on the wing without 

 fatigue than any other bird with which we are familiar. 

 The rest of the tribe are inferior in this respect to the 

 swift ; but they all have the same general character 

 of sternum and. the same style of flight. 



The coracoids in these birds are short and strong ; 

 the clavicle open, but an elliptic arch more than a 

 circular one ; the scapulars are shorter than the ster- 

 num, nearly straight, rather slender, but enlarged a 

 little toward their terminations, which however are 

 pointed. 



Night-feeders, or those which feed only in the dusk 

 or twilight, and rest during the day, have their sternal 

 apparatus considerably different. They have the 

 sternimi short, widened in front, concave at the sides, 

 and the general outline to the rear convex, but 

 divided into three processes by two large notches. 

 The keel well developed, concave in front, convex 

 in the lower line anteriorly, but becoming straight or 

 even concave toward the rear. The lateral processes 

 with elevated points. The coracoids round in the 

 middle of the bone, but enlarged at the heads, and 

 with a pointed process on their posterior sides, near 

 their junction with the sternum. The furcal bone 

 open, but slender, and the sides not so much arched 

 as in the swift. Subjoined there is a representation of 

 these bones in the common goat-sucker of the size of 

 nature. 



The cuckoo is the bird whose sternal apparatus 

 most resembles that of the goat-sucker ; and though 

 the one is a day feeder and the other a night or twi- 

 light one, there is a verv considerable resemblance in 



