Dave Bevan / Pair of Sand martins (Riparia riparia) feeding chicks, Carmarthenshire, Wales, UK, July.

Robin Chittenden / House martin (Delichon urbicum) group on ground, collecting sand for nests. Cyprus. April.

Robin Chittenden / House martin (Delichon urbicum) on ground, collecting sand for nest. Cyprus. April.

Dave Bevan / Sand martin (Riparia riparia) flying to nest hole and feeding chick, Carmarthenshire, Wales, UK, June.

Dave Bevan / Slow motion clip of a Sand martin (Riparia riparia) feeding chick at entrance to nest hole, Carmarthenshire, Wales, UK, May.

Dave Bevan / Pair of Sand martins (Riparia riparia) at nest hole in bank of coal waste, with another trying to land at the same hole, Carmarthenshire, Wales, UK, April.

Dave Bevan / Pairs of Sand martins (Riparia riparia) at entrances to nest holes in bank of coal waste, Carmarthenshire, Wales, UK, April.

Dave Bevan / Flock of Sand martins (Riparia riparia) preening, perched on tree roots adjacent to nesting bank, Carmarthenshire, Wales, UK, April.

Dave Bevan / Slow motion clip of a Sand martin (Riparia riparia) digging nest hole in a bank of waste coal, Carmarthenshire, Wales, UK, April.

Dave Bevan / Slow motion clip of a pair of Sand martins (Riparia riparia) at nest hole, chasing away an intruder, Carmarthenshire, Wales, UK, April.

Dave Bevan / Slow motion clip of a Sand martin (Riparia riparia) flying to nest hole and starting to dig before mate arrives to protect entrance, Carmarthenshire, Wales, UK, April.

Phil Savoie / Sand Martin (Riparia riparia) in flight catching insects over the Madison River, Montana, USA. May.

Phil Savoie / Reflection of Sand Martin (Riparia riparia) hunting Speckled mayfly (Callibaetis sp.) Madison River, Montana, USA, May.

Phil Savoie / Sand martin (Riparia riparia) perched on wire, Madison, Montana, USA, June.

Phil Savoie / Sand martin (Riparia riparia) in flight, hunting insects above the Madison River, Montana, USA, June.

Loic Poidevin / Sand martin (Riparia riparia) feeding chicks on nest, Brittany, France, June

Loic Poidevin / Sand martin (Riparia riparia) feeding chicks on nest, Brittany, France, June

John Waters / Sand martin (Riparia riparia) about to grab swan feather on surface of River Wye to line its nest located nearby, Herefordshire, UK, May.

John Waters / Sand martin (Riparia riparia) taking swan feather from surface of River Wy to line its nest located nearby, Herefordshire, UK, May.

Pal Hermansen / Sand martins (Riparia riparia) chicks calling, begging for food, in nest, Norway, July.

Loic Poidevin / Sand martins (Riparia riparia) group of three on barbed wire, Vendee, France, July

Loic Poidevin / Sand martins (Riparia riparia) group of six on barbed wire, Vendee, France, July

Jussi Murtosaari / Sand martin (Riparia riparia), at the nest, North Karelia, Finland, June.

Cyril Ruoso / Barn swallow (Hirundo rustica) and Sand martin (Riparia riparia) perched, France.

David Tipling / Sand martin (Riparia riparia) at nest in sea cliff, North Norfolk, UK, June.

David Tipling / Sand martin (Riparia riparia) leaving nest in cliff, Salthouse, Norfolk, UK, June.

David Tipling / Sand martin (Riparia riparia) feeding young in nest hole at colony in sandstone cliffs, North Norfolk, UK, June.

David Tipling / Sand martin (Riparia riparia) leaving nest at colony in sea cliff, North Norfolk, UK, June.

Mick Jenner / Common kingfisher (Alcedo atthis) stunning and eating sand eel prey, River Looe, Cornwall, England, UK, June.

Markus Varesvuo / Sand martin (Riparia riparia) in flight over water, Uto, Finland, July.

David Pattyn / Sand martin (Riparia riparia) sitting on wires during migration. Greece. May

Juan Manuel Borrero / Illustration of Hirundinidae family: Common Sand Martin (Riparia riparia), Northen House-Martin (Delichon urbicum), Common Swift (Apus apus) and Barn Swallow (Hirundo rustica). Pencil and watercolor p...

Martin H Smith / Aerial view of Common seals {Phoca vitulina} on sand spit, Blakeney point, Norfolk, UK

Martin H Smith / Aerial view Common seals {Phoca vitulina} on sand spit, Blakeney point, Norfolk, UK

Martin H Smith / Aerial view of sand spit with Common seal colony {Phoca vitulina} Blakeney point, Norfolk

Natalie Clements / Colony of Sandmartins (Riparia riparia) entering nesting holes in cliff. Multiple birds enter and leave frame, Abergavenney, Wales, June.

Natalie Clements / Sandmartins (Riparia riparia) landing outside of nesting holes in cliff, as others peer out of them, Abergavenney, Wales, June.

Natalie Clements / Sandmartins (Riparia riparia) perching outside of nest holes with chicks inside begging for food. Two enter and one leaves frame as another flies through, Abergavenney, Wales, June.

Natalie Clements / Sandmartins (Riparia riparia) entering frame and landing on cliff at nesting site, with some hovering near cliff and leaving frame, Abergavenney, Wales, UK, June.

Natalie Clements / Sandmartins (Riparia riparia) entering frame and feeding chicks in holes in bank, with some chicks peering out of the holes, Abergavenney, Wales, June.

Natalie Clements / Sandmartin (Riparia riparia) enters frame and enters nest with chick in it, as another lands outside entrance of nest hole above before turning around and leaving frame, Abergavenney, Wales, June.

Philippe Clement / Common sand martin (Riparia riparia) in flight, silhouette against white background. Digitally enhanced silhouette.

David Tipling / Sand martin (Riparia riparia) arriving at entrance to nest made in drainage pipe in a wall, with three hungry chicks waiting to be fed, Fairburn Ings RSPB Reserve, Yorkshire, UK. June.

Nick Upton / Pair of Sand martins (Riparia riparia) flying to nesting colony in coastal sand cliff, Cornwall, UK, April.

Nick Upton / Sand martin (Riparia riparia) flying overhead near coastal nesting colony, Cornwall, UK, April.

David Tipling / Sand martin (Riparia riparia) returning to nesting hole in cliff to feed chicks, North Norfolk, England, UK. June.

David Tipling / Sand martin (Riparia riparia) returning to nesting hole in cliff to feed chicks, North Norfolk, England, UK. June.

David Tipling / Pair of Sand martin (Riparia riparia) at entrance to nesting hole in cliff colony, North Norfolk, England, UK. June.

David Tipling / Sand martin (Riparia riparia) watching over chicks in nesting holes at cliff colony, North Norfolk, England, UK. June.

David Tipling / Sand martin (Riparia riparia) flying towards the cliff colony, North Norfolk, England, UK. June.

Terry Whittaker / Sand martins (Riparia riparia) flying to and from their nests in old drainage pipes along River Mersey retaining walls. Greater Manchester, UK.

Terry Whittaker / Sand martins (Riparia riparia) flying into colony nests flooded by rising River Tame, Greater Manchester, UK.

Terry Whittaker / Sand martins (Riparia riparia) flying into colony nests flooded by rising River Tame, Greater Manchester, UK.

Terry Whittaker / Sand martins (Riparia riparia) fighting over new nests in bank of River Tame, Greater Manchester, UK.

Terry Whittaker / Sand martin (Riparia riparia) returning to nest in bank of River Tame then excavating earth from inside, Greater Manchester, UK.

Nick Upton / Sand martins (Riparia riparia), Swallows (Hirundo rustica) and House martins (Delichon urbicum) perched and preening on power lines, gathered ahead of their autumn migration, Gloucestershire, UK, Sept...

Robin Chittenden / Sand martin (Riparia riparia) juvenile, Norfolk, England, UK.September.

Robin Chittenden / Sand martin (Riparia riparia) juvenile, Norfolk, England, UK. September.

Robin Chittenden / Sand martin (Riparia riparia) juvenile, Norfolk, England, UK. September.

Nick Upton / Sand martin (Riparia riparia) landing to join others and three Swallows (Hirundo rustica) perched on power lines as a mixed species group of hirundines gathers ahead of their autumn migration, Glouces...

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks, nesting in old drainage pipe along River Mersey retaining wall. Greater Manchester, England, UK. June.

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks, nesting in old drainage pipe along River Mersey retaining wall. Greater Manchester, England, UK. June.

Terry Whittaker / Sand martin (Riparia riparia) pair at nest hole entrance on river bank. River Tame, Reddish Vale Country Park, Greater Manchester, England, UK. April.

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks on nest in old drainage pipe along River Mersey retaining wall. Greater Manchester, England, UK. May 2020.

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks nesting in old drainpipes along River Mersey retaining wall. Greater Manchester, England, UK. May 2020.

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks at nest in in old drainage pipe along River Mersey retaining wall. Greater Manchester, England, UK. June.

Terry Whittaker / Sand martin (Riparia riparia) adults feeding chicks nesting in old drainage pipes along River Mersey retaining wall. Greater Manchester, England. June.

Terry Whittaker / Sand martin (Riparia riparia) feeding chicks on nest in old drainage pipe along River Mersey retaining wall. Greater Manchester, England. June.

David Perpinan / Sand martin (Riparia riparia) entering nest in sand bank and leaving with a faecal sac, Scotland, June.