Sand martin
Riparia riparia
Grey brown above. White throat and belly separated by a brown band across the chest. Underwings are dark grey, brown.
Habitat: look for sand martins along sandy riverbanks, cliffs and gravel pits. Can often be seen feeding over water.
Distribution: a summer visitor throughout most of the UK, except the north of Scotland.
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Sand martin showing the brown band across the chest. (northeastwildlife.co.uk)
Not to be confused with
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Swallow
Swallows have much longer tail streamers and a red throat. (Amy Lewis/WTML)

Swift
Swifts are dark brown with scythe shaped wings (northeastwildlife.co.uk)

House martin
House martins have a pure white underside. (blickwinkel/Alamy)