Sand martins excavate nest tunnels in sandy riverbanks and quarry faces, with welfare challenges from riverbank erosion, flooding of nest tunnels, and nest site competition with rats.
Sand martin nests flooded during rain events drown eggs and chicks if the colony is in low-lying river banks. Bank erosion from high river flows undermines tunnels, causing structural collapse that kills incubating adults or chicks. Rat predation at colony sites causes catastrophic losses when rats excavate multiple tunnels systematically. Natural banks used by sand martins conflict with river management operations including erosion control works during the breeding season. Artificial banks require annual maintenance to remain suitable — blocked or collapsed artificial bank tubes reduce colony productivity.