TAILS OF BIEDS. 31 



and two backwards. This occurs in many families of birds not otherwise related 

 either in structure or habits. Examples : Wryneck ( Yunx torquilla), Common 

 Cuckoo (Cuculus canorus), Indian Koel (Uudynamys honorata), Eed-and-Blue 

 Macaw (Ara macao). 



II. The Walking or Wading [Cursorial or Grallatorial) type. In this form 

 the foot has the grasping power, but is especially adapted for walking on the 

 ground. The hind toe is elevated above the level of the others, and reduced in 

 size or totally lost. In some wading birds the intervals between the toes are 

 completely or partially webbed. Examples : Apteryx (A. oioeni), Pheasant 

 {Phasianus colchicus), Heron {Ardea einerea), Pheasant-tailed Jajana (Hydro- 

 pJiasianus chirurgus). Moorhen (GalUnula chloropus), Red-necked Avocet 

 {Reeurvirostra avocetta). 



III. The Swimming or Natatorial type. By the development of webs between 

 the toes the foot is transformed into a swimming instrument, usually with much 

 loss of its power of perching and running. 



(a) The Lohate modification. The toes not united together by webs, but 

 furnished with lobes or flaps along the sides, as in the Coot {Fulica atra), Crested 

 Grebe (Podiceps cristatus), and Grey Phalarope (P. fulicarius). 



ijb) The ordinary Palmate modification. All the front toes united by webs. 

 The hind toe free, as in the Wild Duck {Anas boscas), Black-headed Gull (Lams 

 ridibundus), Skimmer (Rhynchops flavirostris). 



(c) The Totipalmate modification. Webs not only between the front toes, but 

 also extending between the second and first, or hind toe ; so that all four are 

 united together, as in the Pelican (Pelicanus onocrotalus) (Nat. Hist. Museum). 



TAIL OF BIRDS. 



In the extinct Jurassic bird, the ArchcBopteryx, the skeleton of the tail was 

 elongated and consisted of about twenty free vertebrae. In all existing birds it 

 is short. Among these the Eatit^e have the caudal vertebrae mostly free and 

 gradually diminishing in size, a primitive condition, also seen in the early state 

 of all birds. In the majority, however, a certain number of the terminal verte- 

 brae become fused together and assume a peculiar shape, constituting the pygostyle, 

 or "ploughshare bone,'' which supports the rectrices or tail-feathers and the uropy- 

 gial oil-gland. 



The feathers of the tail consist of the large quill-feathers, or rectrices, and the 

 upper and lower coverts, or tectrices. The rectrices are so called because of their 

 action in directing flight. They are arranged in pairs and are usVially 12 in 

 number; less commonly 10, 14, 16, or 18, and very exceptionally fewer than 10 

 or more than 18. They radiate more or less from the pygostyle, the innermost 

 pair being placed above the level of the others. As a rule the upper coverts are 

 shorter and fewer than the lower, but in the Peacock they are far longer than 

 the rectrices, and form the gorgeous train which distinguishes that bird. 



Form of the Tail. The tail may be — 



(i.) Even at the end, "truncated," as in the Lapwing (F. vulgaris), 12 rectrices. 



