By Jane Mower
BBC News, London
Some sparrows have been ringed
Rummaging through the undergrowth of a back garden in central London, nothing can shift the focus of Dr Nancy Ockendon and Chris Orsman.
Binoculars in hand they are looking for signs of nesting and listening out for the sound of chirping male birds.
Their dedication is all in the name of one of London's best-loved garden visitors, the sparrow.
In the last decade sparrows have significantly declined in London and have all but disappeared from some parks.
This "dramatic decline" prompted a study by the Royal Society for the Protection of Birds (RSPB) which aims to save London's sparrows.
Symbol of wildlife
Now, almost half-way through the London House Sparrow Project, Dr Ockendon and her research assistant Mr Orsman are busy preparing for a second breeding season.
This is part of a large-scale feeding experiment being conducted to see whether giving sparrows more food will help numbers recover.
They are closely monitoring 65 sites, selected in 2004, each with at least six breeding pairs and access to at least three volunteers' gardens.
Volunteers are asked to put meal worms out twice a day
At one site the birds are fed as normal and at the other, meal worms are put out twice a day between April and July.
During March and April the researchers visit the sites looking for "chirping males and signs of possible nesting sites".
Then throughout the breeding season visits are made once a month to count the number of fledglings.
Nest boxes were also put in so researchers could keep a close eye on the number of eggs laid and survival rates.
"Because house sparrows have such a strong association with London, people want to know what's happening and so we didn't find it too difficult to recruit volunteers," Mr Orsman said.
Between 1977 and 2000, house sparrow (Passer domesticus) numbers in the UK declined by 65%.
In London they have almost completely disappeared from the central Royal Parks and most notably in Kensington Palace Gardens numbers fell from around 2,500 in the 1920s to just eight in 2001.
Mr Orsman stressed that with two years of the project left to run "nothing conclusive can be drawn yet".
HOUSE SPARROW FACTS
In their lifetime most sparrows will usually only fly up to 2km from where they were hatched
Sparrows can have up to four clutches in one year, and the average clutch size is four
The oldest known British house sparrow was 12 years old
Sparrows nest from March until July, usually under the eaves of buildings, but occasionally in dense shrubs and bushes
But he hopes their results can be used to successfully stop numbers falling in London.
"If we can demonstrate that by putting mealworms out we are significantly benefiting the breeding success and survival of house sparrows then we might be able to put forward proposals for an insect-friendly way of managing open spaces and gardening.
"Sparrows are an important symbol of London wildlife and we're trying to find ways that people can help them to recover."