The group is hoping to discover what is causing the alarming fall in the numbers of the unassuming dull brown or grey bird. In 1925 there were 2,603 house sparrows recorded in Kensington Gardens but this spring just four were found. The decline has happened gradually. A count in 1948 recorded 885 house sparrows, while in 1975 there were 544 and in 1995 the number had dropped to just 46.