Volunteers were asked to look for bumblebee nests
Gardens are key habitats for the UK's nesting bumblebees, a survey suggests.
Scientists have found that the bees' nests are more likely to be located in gardens than in habitats such as woodlands or grasslands.
The study, reported in the Journal of Applied Ecology, could aid bumblebee conservation work.
The brightly coloured insects have suffered a dramatic drop in numbers. In recent years, three species have become extinct in Britain.
And for at least five of the UK's 25 species, special measures are being taken to stop their numbers falling further.
Scientists believe that finding out more about the animals' habitats could help them to better understand and address some of the factors responsible for the decline.
The British Bumblebee Nest Survey took place during the summer of 2004.
Volunteers were asked to look at an area of their garden plus one of six different countryside habitats for 20 minutes and to record whether any bumblebee nests were present or not.
Juliet Osbourne, lead author of the paper from Rothamsted Research, Hertfordshire, said: "Bumblebee nests are found underground or on the surface in areas like long grass or compost heaps, and people were basically looking for the traffic of bumblebees moving backwards and forwards from an entrance."
The collated results from the 719 volunteers revealed that gardens contained a high density of bumblebee nests - an average of 36 per hectare. Hedgerows, fence lines and woodland edges had an average of 20-37 nests per hectare; woodland and grassland habitats had the lowest densities (11-15 nests per hectare).
Dr Osbourne said: "It shows that gardens are actually providing a very good habitat for our bumblebees, and are actually quite a lot better than some of the habitats in the countryside."
She added that the findings were not unexpected as there were many reasons why gardens were attractive nesting sites.
"The diversity of garden features and gardening styles provide a large variety of potential nesting sites compared to more uniform countryside habitats," she explained:
"Areas with gardens have a high concentration of boundary features, such as hedges, fences and garden buildings, which are suitable for nesting."
Dr Osbourne added that gardeners could aid conservation efforts by encouraging more bumblebees to their gardens.
She said: "There is a lot people can do. They could just leave an area where the grass isn't mowed or grow bright scented flowers throughout March to September."