THE PERCHING BIEDS. 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 {Hirmido gidturalis), 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, 

 whiclv build in tlie rafters year by year. Tlie other two swallows tre 

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

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



The house martin {Cliilldon lagopoda), as its name suggests, builds 

 its nest iir human domiciles, while the cliff martin (Ptyonopracne rupes- 

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

 it makes its nest under the 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 brown above and white below. 



The sand martin {Cotilc ripariu) nests 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 i\Iongolia, I frequently came across regular warrens, 

 excavated by these little birds in low banks, or even in the sides 

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

 seen, evidently gathered together preparatory to the migration south- 

 ward. 



