OF THE BEITISH ISLANDS. 27 



secured in Europe, of which three were shot in the British Islands. In 1860 

 another example was procured at Sarepta, and in the autumn of the same year 

 an invasion of the plains of China is recorded; whilst in 1863 a large band 

 invaded the west, and birds were obtained in most parts of Europe, from 

 Scandinavia in the north to Italy in the south. The normal breeding area of 

 this Sand-Grouse is in Central Asia, on the vast steppes and salt plains of North- 

 east Turkestan, Mongolia, and Dauria; whilst in winter it includes West 

 Turkestan, the Kirghiz Steppes, and North China. 



Allied forms. None very closely related, with the exception of Syrrhaptes 

 tibetanus, an inhabitant of the tablelands of Thibet, a much larger species (the 

 largest of the order), with no black patch on the abdomen. 



Habits. We may appropriately preface our account of the habits of this 

 species by quoting what we have already written respecting its irruptic movements, 

 in our volume on the migration of birds.* These irruptic movements of birds 

 cannot be classed either as normal migration or as nomadic migration, although 

 many naturalists appear to think that they are nothing but variations of one or 

 other of these habits. Irruptic movements are entirely abnormal movements and 

 only occur at irregular intervals: waves of avine life that burst from certain 

 centres, eventually exhausting themselves, and ultimately ending in dissolution 

 and death. Gatke classes these irruptic movements as phenomena of migration, 

 and attributes them to meteorological influences, probably of an exceptional 

 character ; but I should be disposed to attribute them to an excess of population 

 flowing from an overcrowded area, taking of course the direction of the normal 

 migration at whichever season the movement may be initiated. As an example 

 of this irruptic movement we have the intensely interesting wanderings of Pallas's 

 Sand-Grouse, from Central Asia, that have from time to time extended to 

 Western Europe with startling suddenness. This species for the past fifty years 

 or so has evidently been in a highly restless and disturbed state, and from time to 

 time great waves of individuals have been thrown out, apparently to relieve a 

 congested area of distribution. Pallas's Sand-Grouse normally is an inhabitant 

 of the vast plains or steppes that stretch continuously from North-east Turkestan 

 and South Siberia to Mongolia. In the north it is a migratory bird, and the 

 winter range base extends into North China in the east, and the Kirghiz Steppes 

 north of the Aral Sea in the west. Until 1859 this species was practically 

 unknown to western ornithologists, although Russian naturalists had met with it 

 from time to time in its far eastern habitat. In that year, however, the first signs 

 of the coming irruptions broke into Europe, and examples of the Sand-Grouse 

 were obtained in Poland, Jutland, Holland, and in the British Islands. It is 

 interesting to note that the evident direction of this avine wave followed a north- 

 westerly course from the Kirghiz Steppes, almost exactly corresponding with the 

 * The Migration of Birds, pp. 257-260 (Amended Edition). 



