GREBE. 



669 



recovering the foot, that is in bringing it in advance 

 through the water preparatory for a second stroke, 

 the mechanism performs its office with equal perfec- 

 tion. When the full bent of the stroke is given, all 

 the joints and membranes of the foot are at their 

 greatest degree of tension, so that the foot strikes as 

 if it were one expansion of solid matter, and the 

 membranous border of the tarsus, together with the 

 flat surface of the bone, assist in giving additional 

 effect. As soon, however, as the stroke is given the 

 whole foot relaxes, the tarsus turns with its thin edge 

 to the front, and thus the foot is advanced and a new 

 impulse given before the momentum of the body is 

 visibly diminished. No feathering of an oar, even 

 by a most expert rower, can at all compare with this 

 recovering of the grebe's foot, though that manoeuvre 

 with the oar is a sort of humble imitation. 



Grebes being chiefly inhabitants of those waters in 

 which there is a good deal of vegetation, derive con- 

 siderable advantage from the division of the foot, and 

 they get additional power from the great length of 

 the toe. The wings also keep stroke with the loot ; 

 and from their hollow shape and their linn texture, 

 they may assist a little in the forward tin it ion, yet the 

 chief use of them is in directing the course of the 

 bird, especially in ascent and descent; so that, thus 

 furnished, the grebe has nearly the same command 

 of itself in the water of the tangled pools as the divers 

 have in the free water of the ocean. 



The form, the covering, and indeed every thing 

 connected with these birds, is a beautiful instance of 

 the adaptation of structure to habit. No plumage 

 resists the water better, or gets through it with less 

 friction. Indeed the surface of the grebes is strongly 

 repcllant of water when thev are alive ; and though 

 it is not easy to say in what this property of the fea- 

 thers of binl which swim under water consists, the 

 knowledge of it would be exceedingly useful in deter- 

 mining by \vhat means, other tlvm mere form and 

 smoothness of surface, a vessel conld be propelled 

 through the water. The grebes afford a very con- 

 vincing proof that this property is not obtained by 

 the application to the feathers of an oil secreted by 

 the glands on the rump of birds ; but that, on the 

 other hand, it must extend to the whole surface, to 

 every feather, down esen to the finest filaments of 

 the webs. That ii i< something connected with life 

 in the birds we are certain, because the dead feathers 

 of those birds are soon wetted : and that it is not put 

 on by any action of the bill, becaiie it is just as per- 

 fect in those parts which the bird tannot reach with 

 its bill as in those which it can reach. 



There is another provision in the covering of the 

 grebes which shows how well they are organised for 

 bearing the temperature, as well as the other influence 

 of the water. They are covered immediately under 

 the skin with a considerable layer of fat ; and that fat 

 is of the same oily nature as the fat on the under 

 sides of many swimming birds, and also on the bodies 

 of whales. This fat gives a disagreeable rancid, or 

 what is usually termed " a fishy flavour" to the flesh 

 of grebes ; but it is possible that, as is the case with 

 many of the marine birds, this flavour might be, in 

 great part at least, removed by burying for some time 

 in fresh mould. This flavour appears to be a subject 

 respecting which there are very general mistakes. 

 The term " fishy " seems to be a misnomer, for it 

 is not easy to see how feeding upon fish could com- 

 mutacate this flavour ; because it is the flavour of a 



substance which has undergone two complete changes, 

 first, assimilation by the digestive process, and secondly, 

 secretion by those tissues in which it is lodged. The 

 way in which the particular nature of the food of ani- 

 mals modifies the qualities of their flesh is, however, 

 a subject upon which much information is wanted 

 before any definite conclusions are arrived at. 



These birds are very miscellaneous feeders. They 

 do catch fish, but their bills are not adapted for the 

 capture of very large fishes ; and they are known to 

 feed on many other substances, such as spawn, water 

 beetles, crustaceous and molluscous animals ; and it 

 has been alleged that they sometimes eat the more 

 succulent roots of vegetables, though this is some- 

 what doubtful. They also swallow their own feathers, 

 which they are careful to pull out the moment that 

 they begin to decay; and as these feathers, mixed 

 with the elytra of beetles, and other indigestible mat- 

 ters, are often found in pellets in their stomachs, it 

 has been supposed that they " cast " these pellets in 

 the same manner as owls and other birds of prey cast 

 the indigestible " quids " of their food. 



From their structure, grebes are very awkward 

 upon the land; and therefore they come ashore as 

 seldom as possible, and they are comparatively seldom 

 on the wing. At those seasons when they have 

 recourse to the sea. and the wind blows strongly in 

 shore, they, like the other diving birds, have con- 

 siderable labour in keeping themselves from being 

 strangled, which they endeavour to do by swimming to 

 windward. But though these are times of labour to 

 them, they are also times of plenty ; for the agitation 

 of the water brings up a areat quantity of those sub- 

 stances on which they feed, and so tosses about the 

 smaller fishes that they also become an easy prey. 



The nesting-places of grebes depend a good deal 

 on the nature of their pastures ; those which are more 

 seaward, or inhabit waters destitute of vegetation, 

 nestle in holes of the banks ; whereas those which 

 frequent the reedy and sedgy pools inland form their 

 nests of vegetable substances, concealed in a tuft near 

 the water's edge, and not nnfrequently over its sur- 

 face, if the standing vegetation is capable of support- 

 ing the nest. Those nests consist of a great bunch 

 of vegetable matters, but, as the whole of these are 

 the produce of the waters, they are much coarser 

 than the nests of those birds which seek their mate- 

 rials on hind. The nests of grebes are sometimes 

 flooded, ami the wind sometimes breaks them from 

 their moorings, and drifts them to other places of the 

 pools, without having sustained much injury. On 

 these accounts there have been many mistakes re- 

 specting those nests. It has, for instance, been said, 

 that they are purposely wetted, and that the fermen- 

 tation produced by the humidity of such a mass of 

 vegetable matter generates heat, which greatly 

 assists in hatching the eggs. Now, this mistake, 

 which is a very common one, involves two errors ; 

 one, in the physiology of warm-blooded animals, 

 and a still greater one in the physiology of plants, 

 or rather, perhaps, in the phenomena of decaying or 

 decayed vegetable matter. So far as we know, there 

 is no egg of a warm-blooded animal that ran be 

 quickened into life by any action of heat, if accom- 

 panied with moisture at the same time ; and, on the 

 other hand, the vegetables which grebes, and all 

 other birds which use vegetables, construct their 

 nests of, are past that state in which any moistening of 

 them would produce either heat or fermentation. 



