Slightly larger than Barn Swallows, Red-rumps have a lazier, more floaty flight. They arrive at the beginning of April, well after their cousins, and leave later with the nesting site not so reliant upon Man's proximity, though they do use man-made structures such as bridges and drainage culverts, to the roofs of which they stick their closed, tunnel-entrance, mud nest.
They mate inside their nest with the tunnel entrance preventing an excess of males during mating.
Despite their beautiful appearance they can be aggressive towards other birds and quite often appropriate Barn Swallow nests if they so wish - if there are recently hatched chicks in any such nest these are summarily ejected to die on the ground.
With a pale, faintly streaked breast, a rufous nape and a pale rump with rusty tinge, it is difficult to mistake them for a Barn Swallow, but the best diagnostic difference is the absence of a dark chin-strap if seen from below and the large whitish rump if seen from above. The rump becomes redder with age. Their flight diagnostic is a greater prevalence for gliding than Barn Swallows.
There is an excellent picture below of the two different species over water that shows the different plumage of the Red-rumped as opposed to the Barn. Note the absence of any chin-strap, the orange neck, the white rump tinged with red and the absence of any windows in the tail.
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