386 Lieut. -Col. R. Meinertzbagen on [Ibis, 



from outside tbe Paloearctic Region, is well illustrated by 

 tlie Grey Parrot in Equatorial Africa. Tbis bird, formerly 

 unknown mucb east of Ugauda, bas rapidly extended its 

 rauge across tbe i\Iau Plateau and Rift Valley, and will ere 

 long find itself on Mount Kenya and tbence to tbe east 

 coast of Africa. 



Gradual contraction of range from natural causes may be 

 due to meteorological or climatic conditions. Gaetke {' Birds 

 of Heligolaud ') quotes tbe erosion of tbe Heligoland cliffs 

 as partly destroying the breeding-baunts of tbe Guillemot 

 and Razorbill. A cyclone in INIauritius almost exterminated 

 tbe local species of ^Martin. Tbe sudden rising of water on 

 an artificial lake in Balucbistan completely destroyed many 

 dozens of nests of a Grebe, together witb many hundreds of 

 their eggs, and tbe whole colony of breeding-birds moved 

 that night and have not since returned to that lake as a 

 breeding-species. 



Or contraction may be due to inability to establish a 

 migratory habit, which we see after severe winters among 

 some of our own resident forms ; or to an iusufiiciently 

 developed migratory habit, as witb certain communities of 

 Redwings, Fieldfares, and Starlings, who perish in the 

 south of England and Ireland in very severe weather rather 

 than continue their passage to south-western Europe, as do 

 other communities of tbe same species who have developed 

 an increased migratory line of flight. 



Or contraction may be due to expansion in range of some 

 other species which becomes an evicting factor. Tbe Jack- 

 daw is believed to have been largely responsible for driving 

 tbe Chough from tbe cliffs of southern and western England. 

 The House-Sparrow, in extending its range in Russian Tur- 

 kestan, has supplanted tbe Tree-Sparrow, and bas evicted 

 tbe House- and Sand-Martin from many nesting-haunts in 

 England. Tbe Puffin bas replaced the Manx Shearwater 

 in some of the islands of the Inner Hebrides. 



Food-supply will also contract the range of a species, 

 thouirh this is usually only a temporary inconvenience. 



