The BBC has teamed up with members of Beddington Farmlands Bird Group and Tower 42 Bird Study Group to study bird migration over London.

Coordinated watches are logging migrating birds as they pass over the capital, and the BBC has been filming the study as part of a Natural World documentary.

A surprising selection of birds pass over London in large numbers. There have been sightings of birds of prey and waders as well as smaller birds. Many often stay for a few days, at sites like Beddington Farmlands, to re-fuel and rest.

Peter Alfrey, a naturalist involved with both bird groups said: “The birds have spent the winter to the south and are now migrating to areas where they will breed.

“Recently an Osprey was tracked over London by observers at different posts. It was first seen at Beddington Farmlands, then passed over Central London and was seen again at Stoke Newington, North London. It took 25 minutes for the bird to move from south to north London.

“Ospreys winter in sub-Saharan Africa and the bird was making its way to either the north of England, Scotland or to Scandinavia.”

It is hoped the study will determine the speed, height and direction of the birds.

To this end birdwatchers have been positioned at Beddington Farmlands and on Tower 42, a skyscraper in central London with views stretching across the capital.

The Beddington Farmlands Bird Group is dedicated to the promotion, recording, preservation and conservation of the Beddington Farmlands site.

The site covers about 400 acres of mixed habitats, including a small lake, flooded grassland area and meadowland, and environmentalists want the area to become London's biggest nature reserve.

To see some of the stunning photographs taken during the study and for details of the development of the reserve visit Mr Alfrey’s blog at peteralfreybirdingnotebook.blogspot.com.

To join a mailing list for Beddington Farmlands news and to receive information about bird walks and events email littleoakgroup@btinternet.com.