The Sand Martin is the only Swedish swallow or martin that digs its own nest, and it always breeds in colonies in open sand.
Nest site: a 60–90 cm long tunnel dug straight into a vertical, eroding sandbank, with a lined nest chamber at the far end.
Colony: colonies can hold anything from a dozen to several hundred pairs, with closely packed nest holes in the same bank.
Digging: both sexes dig together, and 4–6 eggs are laid on a bed of straw and feathers in the chamber.
Because the banks become overgrown or collapse, the species is wholly dependent on fresh, bare sand constantly being exposed, for example in gravel pits.