sand martin
US /sænd ˈmɑːr.tɪn/
UK /sænd ˈmɑːr.tɪn/
1.
a small, brown migratory bird of the swallow family, typically nesting in tunnels dug into sandy banks.
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We watched the sand martins darting over the river.
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The cliff face was dotted with the nests of sand martins.