THE PERCHING BIRDS. 143 



Finally we come to the swallows and martins represented by some 

 six species, three of each. The common swallow of these parts is the 

 eastern house swallow {Hirundo gutturalis), which is allowed to build 

 in the ceilings and eaves of native houses. Both the Chinese and 

 Mongols consider it extremely lucky to have swallows build in their dwel- 

 lings, and in many places every house and tent has its pair of swallows, 

 which build in the rafters year by year. The other two swallows ire 

 the Nipal striped swallow (H. nipalensis), which has a striped breast, 

 and Tytler's swallow (H. tytleri), which keeps more to the wild parts. 



The house martin (Chilidon lagopoda), as its name suggests, builds 

 its nest in human domiciles, while the cliff martin [Ptyonopracne rupes- 

 tris) keeps to the rocky ravines of the mountainous districts, where 

 it makes its nest under tlie overhanging rocks and in caves. It is 

 about the same size as the swallow, but has a much shorter tail, and 

 is of a dark bro\ra above and white below. 



The sand martin {Cotile riparia) nest« in long tunnels, which it 

 excavates in sandy banks and cliffs. It is considerably smaller than 

 the crag martin, though of about the same shape and colour. When 

 travelling in Inner Mongolia, I frequently came across regular warrens, 

 excavated by these Httle birds in low banks, or even in thie sides 

 of disused wells. In places immense flocks of these birds were also 

 seen, evidently gathered together preparatory to the migration south- 

 ward. 



