Sparrows are a family of small passerine birds. They are also known as true sparrows, or Old World sparrows, names also used for a particular genus of the family, Passer. Dying species Saving sparrows has become a matter of urgency as the birds have been recognised as an indicator of environmental health and urban biodiversity. ... But why are sparrows declining in countries which are more bird-friendly? There are a number of reasons, mostly linked to loss of habitat.