KESTREL FALCON. 329 



Vakiations. — The males vary little in size. The grey of the 

 head is sometimes tinged with brown ; the red of the upper 

 parts varies considerably in tint ; the spots in size and form ; 

 and the tail may retain traces of its original ten bars, which 

 on the middle feathers may be either direct or alternate, with 

 the exception of the last, which is always continuous. The 

 females assume more grey on the head, rump, and tail as they 

 become older. The ccecal appendages of the intestine vary in 

 size, from a quarter of an inch in length to half a twelfth ; or 

 they may be wanting on one or on both sides. 



Change of Plumage. — When fresh, the colours of the plu- 

 mage are much richer than toward the period of renewal, when 

 they are sometimes much faded. 



Habits. — The peculiar habits of this beautiful Falcon are 

 well adapted for illustrating the range of vision of the diurnal 

 rapacious birds. It has been alleged that Eagles, Kites, and 

 Ospreys, not to mention other species of the same family, are 

 capable of perceiving a very minute object at a most marvel- 

 lous distance, even from a height at which they seem no larger 

 than a midge or a mote. Experience, however, has led me to 

 discredit such assertions, and to consider them as resulting 

 rather from a vigorous imagination than from actual observa- 

 tion. There is no truth, not even probability, in the assertion 

 that Eagles perceive living prey from a height exceeding a few 

 hundred yards, although it is certain that they can distinguish 

 the carcase of a sheep at a much greater distance. The Hen- 

 harrier, the Sparrow Hawk, and the Kestrel, when searching 

 for small birds, mice, and other objects, fly at a height of from 

 ten to fifty feet. The latter never hovers at a greater dis- 

 tance from the ground than forty feet, and we know that its 

 power of distinguishing its prey does not extend over a much 

 greater range, for in traversing a meadow, it requires to as- 

 sume numerous stations in succession. A Falcon, however, 

 can perceive a Heron or other bird at a vast distance in the air, 

 and I have seen domestic fowls aware of the presence of an 

 Eagle two thousand feet above them. 



