With skylarks singing gloriously in the skies above Richmond Park, signs of spring are returning.

Richmond Park is one of the very few and best breeding areas for skylarks in Greater London but these threatened ground-nesting birds are easily disturbed by dogs and visitors.

Surveys by the British Trust for Ornithology and RSPB suggest that over the last 50 years, skylark populations across the UK have declined by over 65%.

They remain on the RSPB's Red List of birds of "highest conservation priority....needing urgent action".

Conservation charity Friends of Richmond Park has now produced a film to inform visitors about these endangered birds, presented by its patron Clare Balding OBE.

In the seven minute film Clare meets dog owners, bird experts and the park's manager Simon Richards, and explains why signs and skylark protection zones have been installed to alert park visitors to the breeding birds.

Read more: Out of control dogs at Royal Parks putting endangered bird species 'under threat'

Simon says: "We're asking dog owners to keep their dogs on leads and visitors to keep to the main paths in relatively small parts of the park to give the birds a chance to nest and safely raise their young." The protection zones will be in place until the end of July.

You can watch the film at the top of this story. The Friends have urged people to please share it widely with their friends and family.