Birders in the U.S. are supposed to hate European Starlings (Sturnus vulgaris), and there are plenty of reasons to do so.
The species originated in Europe, North Africa, and western-to-central Asia. While mostly abundant there as well, the species has been red-listed in England after populations plummeted by more than 80% over the last 40 years . Other northern European countries have witnessed a similar decline . We can only wish that would happen here.
North American populations have exploded since their introduction in the early 1890s. According to the USDA, starlings cost our country $1.5 million in damage to agricultural crops, the consumption of feed intended for livestock, and in property damage. In one winter, a million starlings can down 27,500 tons of livestock feed, not to mention what is ruined by their accumulated droppings—and latest estimates put the US population at over 200 million birds.
Because they congregate in large flocks of up to 100,000 individuals, starlings are a particular hazard near airports. They can be sucked into jet engines, causing extensive damage. In 2002, a 737 jet had to make an emergency landing at SeaTac airport after hitting a flock of “only” 100 starlings.
Those large flocks have to land somewhere. When they do, their constant racket can be deafening. Starlings cause extensive damage to trees, buildings, and other structures. The droppings from so many birds can actually kill trees, while the weight of the birds can break off branches. Plus, those droppings are highly acidic, which corrodes metal.
Starlings are a direct threat as well, carrying a number of diseases that affect livestock. Twenty-five of these diseases affect humans. For example, Histoplasmosis is a respiratory disease caused by a fungus that lives on starling droppings. Anyone entering a building where starlings roost would do well to take precautions.
In addition to the harm done to human, starlings compete directly with a number of native birds. By stealing both food and nesting cavities from natives such as bluebirds, woodpeckers, Wood Ducks, and especially Purple Martins, they have caused a significant drop in the numbers of those species. In all, starlings might be one of the worst pests ever to invade our continent.
With such a dismal reputation, it might be surprising to learn that starlings have at least one good point. According to an article in the Christian Science Monitor,
Biologist Bud Anderson, with the Falcon Research Group, agrees that the starling invasion has been a disaster for many native species. But he says starlings are not all bad, ecologically speaking. He’s studying peregrine falcons’ comeback in Washington state since the phaseout of the pesticide DDT. “We’re looking at 30 pairs of peregrines and in virtually all those nests we see starlings as one of the main prey items,” he says. “Starlings are helping bring back peregrines.”
That’s wonderful—Peregrine Falcons are welcome to all the starlings they can find. Still, most ecologists, farmers, and federal agencies recommend continuing attempts to kill these destructive aliens. That’s why it came as a shock to find a website devoted to the rescue and rehabilitation of orphaned starling (and House Sparrow) babies. We don’t protect mosquito larvae, we don’t plant noxious weeds, and we shouldn’t try to save birds that don’t belong here, even if they are cute little babies.
In fact, if you maintain bluebird or other nest boxes, it is up to you to prevent starlings or House Sparrows from raising a family there. Do the responsible thing, and oust these invasive pests!
 Snow, D. W. & Perrins, C. M. (1998). The Birds of the Western Palearctic Concise Edition. OUP ISBN 0-19-854099-X.