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individuals, a moderate calculation. The underlying causes of 
this movement were much discussed, although few British naturalists 
are sufficiently acquainted with the physical conditions prevailing 
on the steppes of Mongolia, to approach that difficult problem 
with much likelihood of success. Australia has furnished evidence 
that in that continent some well-known species are liable to appear 
in swarms in certain regions, and after an interval again to disappear ; 
while, even at home, some lessons are suggested by the remarkable 
increase of certain species, e.g. Sturnus vulgaris and Columba enas; 
the last named having of recent years colonised the north-east of 
Scotland, though formerly almost unknown in the most northern 
counties of England as a breeding species. Over-population, as 
long since suggested by Professor Newton, correlated with a scarcity 
of food, may probably continue to be accepted as the prime factor 
in the migration of Syrrhaptes ; at the same time we cannot forget 
that the species is accustomed, in Asia, to traverse vast distances, 
_ for which contingency it is admirably adapted by the development 
_ of the pectoral muscles and the shape of the long wing feathers. 
GENERAL HABITS OF PALLAS SAND GROUSE IN ENGLAND. 
So little has hitherto been written to explain the idiosyncrasies 
of this Sand-grouse, regarded as a British bird, that the writer feels 
that no apology is needed for presenting as full a statement on this 
head, as his own too limited opportunities of outdoor study enable 
him to furnish at the present juncture of events. 
Pallas Sand-grouse has proved, during the summer of 1888 in 
_ England, to be a highly gregarious bird ; constantly affecting the 
company of its fellows. It is possible that it may entertain some 
aversion to the company of other species ; at least it has not been 
_ observed by the writer to associate voluntarily with any other birds. 
In confinement, it has manifested some intolerance on this score. 
_ Thus, an example living at the Zoological Gardens (August) was 
observed to drive away a Woodlark (Alauda arboreus), and a 
second objected to the presence of a Pigeon placed in its enclosure 
_ to solace it supposed loneliness. In a state of nature, this Sand- 
_ grouse flies in parties of four or five birds, but more usually in 
