The house sparrow is one of a handful of birds that most Americans can identify. Even most non-birders recognize this small brown denizen of urban areas. These are the little birds that we see at street corners, around fast food parking lots, and in our backyards, especially if we live in urban areas. Over the millenia, house sparrows have become well-adapted to human habitation. They nest in cavities in human dwelling and take advantage of wasted food. House sparrows became an urban species first in its native Europe, and then adapted well to their new surroundings when they were first introduced to this continent in 1851.
Despite its past success, not all is well with this species. The Royal Society for the Protection of Birds is conducting a study to determine the cause of the house sparrow's decline in the U.K. and possible ways to reverse the trend. Sparrows have declined by 65% in the U.K. over the past quarter century and are almost gone from many of London's parks. The researchers are testing the impact of food supply on breeding success. Specifically they are testing if providing mealworms helps. If it works, the RSPB plans to start a campaign to get homeowners to increase the availability of invertebrates through gardening or feeding.
The house sparrow is declining in North America as well as Europe. While the species is still very common in cities, Christmas Bird Count circles have reported increasingly fewer house sparrow individuals over the past half-century. Reports for the entire United States show a fairly impressive decline. (Click to enlarge.)
Results from the counts in D.C., Maryland, and Virginia show a similar trend. (Click to enlarge.)
In both cases, the numbers of house sparrows per party hour peak in the mid 1960s and fall until the 1990s, when the graph seems to level off.
In some respects, the decline of house sparrows on this continent is a blessing for native bird species. The introduction of house sparrows is a classic case for the havoc invasive species can wreak on ecosystems. House sparrows, being aggressive, frequently outcompete native birds for resources. Where food and nesting space are scarce, this can put native species at risk.
But the house sparrow's decline may be a sign of larger problems. If these historically successful birds are having trouble, could this be a sign of trouble to come for other songbirds? Until we know the causes of their decline, we have to hope that the answer is no.