The environment correspondent is Helen.
Red kites are being flown abroad to help save the Spanish population.
A lack of food and poisoning are some of the factors threatening the birds of prey.
Special permission has been given to take 30 red kites from England and release them in a remote area of Spain.
The hope is that the birds will breed there and save the population.
After almost being wiped out in the UK, the red kite has turned around.
The population is stable enough to support the work that was done in the 1980's and 1990's.
In the 1990s, Ian Evans of Natural England went to Spain to collect wild red kites. The ones coming this week may be from Spain.
He said that the birds they took from Spain in the '90s have done well in Britain.
In the 1990s, red kites in Spain were doing better than in the UK, where years of persecution had pushed the bird to near extinction.
Some parts of southern Spain have gone the other way due to a number of factors.
The reason for taking the birds back to Spain and releasing them in the wild was to secure the future of kites around the world.
Fifteen red kites are being flown to Madrid to be released.
The juvenile birds have most of their feathers and can feed on their own.
The project was kept under wraps until now, but the first 15 birds have already left.
The birds will be fitted with the latest technology for monitoring how they adapt to their new environment before being released.
30 birds will be released this year and 30 more in each of the next two years, according to the RSPB.
He said to find 90 to 100 birds to create a sustainable population. A new breeding nucleus should be created by that.
There have been increases in the number of red kites in Europe in the last few years, but there are still declines in southern Spain, Portugal and Germany. More than 10% of the world's red kites can be found in the UK.
Birds are being sent to Spain. The original effort to rescue British red kites was led by Karl Ivans.
He was involved in the project from the beginning. You are very proud to do something for the environment and for the wonderful species.
The Roy Dennis Wildlife Foundation is one of the groups involved in the project.