The House Martin, Delichon urbica, is a migratory perching bird of the family Hiruninidae. The European range of the House Martin roughly corresponds with that of its relative the Barn Swallow, and it also winters in tropical Africa.
The adult House Martin is steel-blue above with a white rump, and white underparts. Its short legs and toes have white downy feathering. Its bill is black. The young bird is sooty black, and some of the coverts and quills have white tips and edgings. The white rump of the House Martin, very noticeable in flight, should prevent confusion with either the Swallow or Sand Martin.
The House Martin is constant in returning to its old lair, repairing
the nest it built the year before, or making a new one close to the one in which it was reared. The nest is a cup fixed below a suitable ledge. The entrance is so small that the interfering House Sparrow cannot invade once the nest is complete. The mud, added in successive layers, is collected from ponds, streams or puddles. Both birds work at construction.
Undoubtedly the House Martin, before it found man providing shelter in the shape of overhanging eaves, was a cliff and cave dweller. Some colonies of cliff nesting martins still exist. Even on a bare cliff face the bird usually builds below an overhanging rock, and on houses the nests are close under the eaves so that they may be strengthened by attachment above. During construction there are frequent quarrels with trespassing sparrows, but if the sparrow remains in possession of a nest for long, the martins build elsewhere.
At all times the martin is sociable, and many nests are built actually in contact with one another. 4 or 5 white eggs are laid as a rule in early June with second and third broods common, however late nestlings are often left to starve. For weeks after leaving the nest the young congregate in ever increasing flocks which, as the season advances, may be seen gathering in trees or on housetops or on the wires with swallows.
Its food, as well as many of its habits, except those connected with nesting, are similar to those of the swallow.