This is a video of a sand martin breeding colony in Ostvik, Skellefteå, Sweden.
Common insect-eating birds suffer dramatic declines…
New research by Bird Studies Canada (BirdLife Partner in Canada) has highlighted alarming trends in insect-eating birds. In the last two decades alone, populations of many common bug-eating species – such as Sand Martin Riparia riparia, Common Nighthawk Chordeiles minor and Chimney Swift Chaetura pelagica – have declined by over 70%. With many of the birds’ prey species also being important plant pollinators, the consequences may be felt by more than just birds.
See also here.