BIRD. 



479 



though there are others which are much more in the 

 water, or on its surface, there are none which have 

 equal power of wing, or are capable of extending 

 their excursions so far from the land. 



Sternum of the Grallidcc. Though the birds which 

 form this order, even when restricted by leaving out 

 those groups which have been already mentioned in 

 the course of these observations, differ very much in 

 the structure of their bills, yet there is far less diver- 

 sity iu their sternal apparatus than the consideration 

 of the bills, as their chief character, would lead us to 

 suppose. But, when we consider that none of them 

 are habitual fliers, that they fly only for change of 

 place, and that their flight is generally taken by rather 

 short, and swiftly-moving wings, we might be prepared 

 to find that agreement which there is in the sternal 

 apparatus. 



It suits the walking and the wading habits of those 

 birds, and also the tangled herbage through which 

 many of them have to make their way, to have the 

 body narrow in proportion to its depth. The sternum 

 is iii consequence long, and rather narrow, a little 

 enlarged towards the posterior portion, and divided 

 there by four notches of considerable depth, the 

 lateral ones generally the deepest ; the processes 

 between the notches feeble, but generally enlarged at, 

 their extremities, so as to form the posterior outline 

 of the sternum into a convex curve. The crest is 

 generally large, convex below, concave in front, with 

 the angle terminating in a process ; lateral processes 

 not nearly so much developed as in the petrel family ; 

 the basis of the coracoids not nearly so large, and 

 their attachment to the sternum not so firm ; the 

 coracoids are, however, short, stout, and considerably 

 enlarged at the heads, but their position is too parallel 

 to each other, and too much in the general line of the 

 sternum, for giving that stability to the shoulder-joint 

 which is essential to long-continued and rapid flight. 

 The clavicle is elongated, curved forward at the middle 

 of its branches, and directed at their junction through- 

 out the middle part of the anterior edge of the keel, 

 and they are enlarged in breadth toward their junction 

 with the coracoids. The scapulars are rather large, 

 flat, straight for great part of their length, but bent 

 downwards toward the points, so as to have a firm 

 embedment on the back. 



In this latter part of the structure it will be per- 

 ceived that those birds have much more the character 

 <f walking or ground birds, than those of the preceding 

 group, or indeed than any of the water birds which 

 are much in the habit of using the wing, even though 

 not so good fliers for a short time as some of the 

 wading birds are. The enlargement of the clavicle 

 toward the shoulder-joints, the large heads of the 

 coraeoids, and especially the increased size and 

 peculiar form of the scapular, together with the com- 

 paratively loose attachment of the coracoids to the 

 sternum, show that the strength of the shoulder in 

 those birds is not wholly, or even chiefly, based upon 

 the sternum, but that great part of it is connected 

 with the back through the produced shoulder-bone, 

 and being connected with the back, it is, by means of 

 thai, referred to the legs for support. This is not the 

 case so exclusively as in the wingless birds, because 

 all the grallidac can fly occasionally, most of them can 

 fly well, though their flights are rather short, and the 

 wings of them all are ready in turning and wheeling; 

 but still a careful examination of their sternal ap- 

 paratus, as combining the elements of walking and 



the elements of flight, would probably be found a 

 much better ground of classification than any to which 

 systematists have hitherto resorted. We shall give 

 the sternal apparatus of the lapwing, which is a 

 tolerably good runner, and also a ready flier, as nearly 

 an average specimen of the whole. 



Lapwim 



The following cut represents the sternal apparatus 

 of the same bird in profile, and both cuts are of the 

 natural size : 



Profile of the Lapwing. 



Sterna of the Lmncllirostres. As in so far as their 

 aquatic habit, is concerned, the sternal apparatus of 

 all these birds is adapted for the bearing up of their 

 bodies while they float upon the water, there is, 

 independently of their different degrees of adaptation 

 for flight, a general character which runs through the 

 whole order. The largest diameter of the body is 

 reversed as compared with that of the grallida?. 

 These have it vertical, so that they may the more 

 easily make their way among the herbage, and also 

 present the least resistance to the air, and give the 

 greatest scope to the legs in walking, wading, or 

 running. But the flat-billed birds have the body 

 more or less flattened horizontally, as well as the bill, 

 by which means they present to the water a large 

 base in proportion to their weight, and thus swim 

 more lightly. The sternum is elongated, and also 

 increased in width, so as to accommodate itself to 

 this form of the body, and upon the average it is so 

 placed that the centre of gravity of the bird is very 

 nearly over its centre of resistance, so that all parts 

 of it are pressed upon with nearly equal force as the 

 bird floats along. 



The habit of floating along the water is, however, 

 in the different genera and species of these birds, 

 combined with so many modifications of other habits, 

 that it is subject to numerous though slight variations. 

 Those habits are greater or less degrees of flying, 

 walking, and diving ; and, from what has been already 

 said respecting birds of which each of these is the 

 principal habit, it will readily be undeistood, without 



