THE BIRD-LIFE OF LONDON 
more gregarious. Numbers of nests may be built side 
by side, but the colonies are never in proportion to the 
vast gatherings that assemble in autumn before the 
migration south. ‘Their ways at this season are full of 
interest, their daily flights and their evening gatherings 
at osier- and reed-beds, where they roost, being very 
characteristic. 
The adult House Martin has the general colour of 
the upper part glossy steel-blue ; the rump and some ot 
the upper tail-coverts are white ; the wings and tail are 
brownish black, the latter considerably forked ; the under 
parts are white. Bill black; tarsi and toes covered with 
tiny white plumes; irides brown. Length about 54 
inches. ‘The nestling is brownish black above, without 
gloss; the rump is white, as are the under parts, but 
the wings are margined with white, the secondaries 
tipped with the same. 
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