They can live nearly anywhere. Deep in coal mines. The most urban of 'hoods. Isolated farms in agricultural boondocks. Enterprising House Sparrows now even eke out a living in the bowels of giant box stores, resting in the rafters and sweeping down for cleanups on aisle six. But the common denominator with these industrious survivors is people. They are seldom far from our shadow.
An interesting thread began today on the Ohio Birds Listerv by a gentleman who noted what seemed like a shortage of House Sparrows recently. This was an astute observation and he is exactly right. House Sparrows, by almost all reckoning of long-term data, are indeed on the downswing, in Ohio and most of North America.
Handsome, jaunty male House Sparrow, photo courtesy of Wikipedia. Actually a very good-looking bird!
In 1851, a Mr. Nicolas Pike obtained 100 of these birds at $2.00 a pop - $200.00 for the lot. He then released them in Brooklyn, New York in late 1851 and early in 1852, and the rest is history.
House Sparrows quickly usurped a void not filled by our native birds - heavily human-modified habitats. This is why they were so successful so quickly, just as have been many Eurasian weeds. These species of Europe have been adapted to the disturbance wrought by people for thousands of years, in some cases, while the native North American flora and fauna were not. Thus, aliens like the House Sparrow quickly gained the upper hand in North America's newly peopled landscapes.
Lovely female House Sparrow, photo once again courtesy of Wikipedia.
But now, these interesting weaver finch allies (they are not true sparrows) are on the decline. This is not only true in North America, but also in their native range of Europe and Asia, where losses are more disturbing.
Many invasive non-native species go through "boom and bust" cycles. They are brought some place new, perhaps exploit an unexploited niche or outcompete the natives that were present, and enjoy a period of largely unchallenged prosperity. Oftentimes, though, Mother Nature eventually marshals her forces, and predators, changes in habitat, and other factors begin to come into play and drive the invaders out.
Our longest-running systematic bird survey is the Breeding Bird Survey, whose routes have been run all over North America since 1966. Overall, BBS data has shown a 2.6% annual drop in House Sparrow populations.
The National Audubon Society's Christmas Bird Counts have provided a wealth of data on bird populations. The graph above depicts the last 30 years of data on House Sparrows in the United States. Even though the number of CBC's and observers has increased, the trend is clearly downward for House Sparrows.
This is a graph showing the last 30 years of CBC data, published in the Ohio Cardinal for House Sparrows in Ohio, that I put together for the winter 2007-08 winter season issue. And a shameless plug: please support the Ohio Ornithological Society, which publishes the Cardinal, makes possible the Ohio Birds Listserv, produces the quarterly Cerulean newsletter, supports young birders, hosts all manner of interesting conferences, field trips and symposia, and more. JOIN RIGHT HERE!
The above chart once again shows a steady downward trajectory for our friend the House Sparrow.
No one is certain, but it seems as if much of the drop is in agricultural areas. Cleaner farming practices may be to blame, as technological advances lead to less grain spillage and other waste byproducts which provide much sparrow fodder. Increased use of pesticides which in turn reduce available insects for the birds to forage on also may play a role.
Even if a bird species in not native - and much despised to boot - it is still important to monitor their declines and try and ascertain the reasons for drops. After all, even birds like House Sparrows can be indicators of our ecological health.