The environmentally-friendly roof of a new library in Cardiff has two guardians of the feathered variety.
Birds of prey Folly and Madam have been brought in temporarily to keep other birds away from eating seedlings and nesting on the grass sedum roof.
Once grown, the grass topping will help insulate the building in winter, reduce rainwater runoff and protect the roof from UV light to help extend its life.
The birds will guard the roof until building work is completed.
Folly is a male brown Harris Hawk with rusty red markings on his wings while Madam is a cream female Saker Falcon with brown wings.
Both have been trained by Phillippa Hawkins, the keeper of the resident hawk called Dad at the Millennium Stadium.
Dad keeps other birds out of the ground and off the pitch and similarly Folly and Madam will take it in turns to guard the roof.
They will be accompanied by a trained falconer.
Jamie Payne, project manager for the library, said the presence of the birds was aimed at preventing seagulls and other birds from getting too close.
"They are fantastic birds and they look great, I'm sure they will do a good job while they are with us at the library," he said.
"The soil was pumped up on to the roof last month and the sedum grass seeds have been planted.
"The roof is now in a very important and fragile stage of growth so the last thing we want is for birds to fly down and disturb the growing process.
"When it has grown the sedum grass roof is just one of the library's green features which will help to make it the most sustainable buildings in Cardiff."
The grass roof will also reduce heat loss in the summer and assist in the removal of CO2 and other pollutants from the air in the city centre.
The new library building at the southern end of the Hayes in the city centre, is part of the St David's 2 development which will open in 2009.
Rhodri Lewis talks to Philippa Hawkins about how birds of prey will protect the library's roof