143823 House Martin Delichon rubica L 12-13cm. Recognised by overall black-and-white appearance and striking white rump. Sexes are similar. Adult has mainly blue-black upperparts with white rump; underparts are white. Juvenile is similar but underparts are grubby and upperparts are duller. Voice Utters distinctive prrrt call in flight. Twittering song often delivered from overhead wires near nest. Status Locally common summer visitor. Typically constructs hemi-spherical mud nest under house eaves and overhangs, in loose colonies. On migration, often feeds on insects and congregates over freshwater.