374 



The Plover-like Birds 



tinguished by its larger size, much longer bill, and brighter color is the Long- 

 billed Dowitcher (M. scolopaceus), chiefly of the interior and western provinces 

 of North America from Alaska to Mexico, while on the Asiatic side the place is 

 taken by the still larger M. taczanowskii, which breeds in eastern Siberia and in 

 winter visits the Burmese countries. 



THE SHEATH-BILLS 



(Family Chionididce) 



On the extreme southern portions of South America and the adjacent islands, 

 and on the farther Antarctic islands, are found four species of snow-white, Pigeon- 

 like birds known as Sheath-bills, the name being derived from the remarkable 

 saddle-shaped, horny sheath which encircles the base of the upper mandible and 

 partially conceals the circular (holorhinal) nostrils. There have been many dif- 

 ferences of opinion as to the 

 probable relationship of 

 these birds, but after a care- 

 ful and complete dissection 

 of the Kerguelen Island 

 form, Drs. Kidder and Coues 

 conclude that they are "a 

 connecting link, closing the 

 narrow gap between the 

 Plovers and Gulls of the 

 present day," and in their 

 opinion " represent the sur- 

 vivors of an ancestral type 

 - from which both Gull? and 

 v '.---- Plovers have descended." 



On the whole, however, 

 their affinities seem to be 

 rather more with the Chara- 



driida, and they are appropriately placed next to them. As additional characters 

 it may be mentioned that the Sheath-bills are four-toed birds, the anterior toes 

 not being webbed, though there is a slight membrane between the base of the 

 inner and outer toes; the tarsus is reticulated both before and behind and on 

 the carpus there is a curious spur, the use of which is conjectural, as it does not 

 appear to be employed in fighting. The Sheath-bills were formerly very rare 

 in collections, which in a measure accounts for the uncertainty long existing 

 regarding their relationship. 



The four species are placed in two genera, the oldest known being Chionis, 

 in which the face is bare and carunculated about the base of the bill. The oldest 

 and best-known species (C. alba], which makes its home about the southern 



FIG. 127. Lesser Sheath-bill, Chionis minor. 



