One hundred pairs of sand martins have made their homes in coal ash at a Nottinghamshire power station.
The migrating birds, who have travelled from Africa for the summer, have made their nests at Ratcliffe on Soar.
Employees at the power station have created a distinct vertical face in the coal ash to replicate the birds' traditional cliff nesting sites.
Plant manager Gary Ulliot said: "It's something we've worked hard to support."
At present, the chicks are beginning to fledge and towards the end of August they will start their 2,000-mile journey back to Africa.
Sand martins have been coming back to Ratcliffe on Soar in increasing numbers for several years.
Commenting on the nesting site Erin McDaid, from the Nottinghamshire Wildlife Trust, said: "The Wildlife Trust welcomes any efforts to create new habitats for birds.
"But efforts to encourage birds such as the sand martin to return to the Trent Valley are particularly welcomed."
Sand martin numbers dipped in the 1970s and 1980s with a loss of habitat but since then numbers in England have risen.
Nottinghamshire is a stronghold for the birds due to the gravel works along the River Trent creating newly cleared habitats.
In the summer large colonies of sand martins can be found along the banks of the River Trent at Attenborough and at the Idle Valley Nature Reserve, near Retford in Nottinghamshire.