248 PANDION HALIAETUS. 



dergoing fatigue, but also to fix itself in a particular spot with 

 a quivering or undulating motion, in order to watch the pro- 

 per moment for descending. Then, as it has to plunge into 

 the water, or at least is liable to come in contact with it, the 

 plumage of its lower parts is rendered more dense and com- 

 pact than usual, and the elongated tufts seen on the outer side 

 of the tibiic in other hawks, are here replaced by short feathers. 

 On the upper parts, however, the plumage is not more compact 

 than in Eagles or Buzzards. Great rapidity of flight, and the 

 power of executing sudden turnings, are not necessary for 

 this mode of life, and therefore the tail is not so long as in 

 hawks generally, for the Osprey, having spied its prey, merely 

 drops perpendicularly upon it. The peculiar form of its prey, 

 the slippery nature of its surface, and the facility wdiich it has 

 of getting out of reach, render necessary a very powerful in- 

 strument of prehension, and accordingly the foot has the tibia 

 extremely muscular, the tarsus very short, the toes of extreme 

 thickness, and covered beneath with prominent conical points. 

 All the toes are possessed of great mobility, and the lateral can 

 be placed at right angles to the first and third, so as to ensure 

 an ample and secure grasp. The very elongated, well-curved, 

 pointed claws are obviously excellent instruments for this pur- 

 pose ; and while in other hawks they are flat beneath and 

 edged, they are in this rounded, so as when introduced into 

 the soft flesh not to tear it, and at the sametime be readily 

 withdrawn should such a measure be rendered expedient by 

 the bird's having seized a fish too strong for it. The oesophagus 

 and stomach do not differ essentially from those of other birds 

 of the family ; but the intestine is excessively elongated and 

 attenuated. It is the same, but in a less degree, in the Sea- 

 Eagles, which feed partially on fish. And hence it might be 

 inferred that an intestine of this form is best adapted for ex- 

 tracting the nutriment from that sort of food, but how or why 

 does not appear ; and many birds that feed in the same man- 

 ner have short and wide intestines. The capacity of the in- 

 testinal tube of the White-tailed Sea-Eade is not greater than 

 that of the Golden Eagle, although the length is as five to one ; 

 nor is that of the Osprey greater than that of the Buzzard, al- 



