Alfred Hitchcock was right, in a way. Birds can be scary. But the nature of the threat can be a little different than expected. Today, we profile 10 bird species that are able to wreak havoc on the natural environment. Their ability to cause damage is generally caused by human introduction or assistance coupled with their specifically aggressive natural tendencies and adaptations. Here is our rogue’s gallery of the air.
10. European Starling
Mentioned in Shakespeare’s works, the European Starling was deliberately brought over from Europe to North America… and that was a huge mistake. This bad bird became the single most serious avian threat to the North American environment. Rogue starlings have decimated populations of bluebirds, woodpeckers and swallows while ripping into orchards and agricultural fields and forming garrulous flocks that look like scenes from The Birds. Accumulating starling droppings foster the growth of Histoplasma capsulatum, the agent behind histoplasmosis, a disease capable of causing loss of vision and in some cases death. Their massive, messy nests are also considered fire hazards when the fearless birds take over buildings.
A shocking 200 million European Starlings are estimated to live in North America, allowing the damage they inflict to take place on a grand scale. The black birds are adorned with star-like speckles, hence their distinctive name, while their sharp yellow bill enables them to easily dispatch any small bird with which they end up in a fight. Bluebirds and woodpeckers, much loved native birds, are often the worst suffering victims of starlings as they force them from their nests.
9. House Sparrow
A small, introduced killer of native birds, the House Sparrow (alternatively named the English Sparrow) is native to the old world, where it inhabits gardens, parks and agricultural landscapes as well as urban streetscapes. The bird was introduced from the old world by nostalgic settlers who missed its foraging presence and chirping, but this proved disastrous upon its arrival. Beloved bluebird populations started dwindling, while species like swallows also suffered attacks. The House Sparrow may not be a carnivore, but it is bad news for nesters as it trashes nests and injures or kills nestlings and, sometimes, adult birds in attempts to get control over scarce cavity nests, natural sites and nest boxes alike.
The House Sparrow is one of the most significant drivers of declines in native bluebird species declines across North America. As it is small, it is very difficult to exclude the House Sparrow from bluebird nests with baffles, while its tolerance of human settlement gives the already ubiquitous bird an extra advantage. House Sparrow control is legal across the continent as it is not a native bird. Do not confuse this species with the many protected native sparrow species in North America — which are more closely akin to buntings — with the House Sparrow actually being a weaver finch.
8. Canada Goose
Iconic and big, Canada Geese present a problem. On one hand, the species is native to North America, yet the birds encroach on settled areas in unnaturally large numbers and for extended lengths of time, aided by human environmental modifications. Introduction of larger subspecies of the Canada Goose — beyond their normal range — has also led to serious invasion problems, with environmental damage of the worst kinds occurring thanks to roving flocks of locally resident, acclimatized geese. Canada Geese represent threats of the most serious kind to human safety and the environment. This one species is responsible for around 35 percent of aircraft/bird collisions annually, according to the FAA, causing disasters that have cost many human lives.
The emergency landing of an airliner in the Hudson River and a fatal crash in Alaska that killed 24 people were both caused by Canada Geese. People often do not realize is that Canada Goose presence is artificially boosted by unwitting habitat creation in urban and agricultural areas, leading to chronic goose overabundance. The damage is enormous. Rogue flocks of invasive geese trigger erosion and large scale habitat loss. The voracious geese overgraze, causing erosion near watercourses, destroying fish and bird habitats, while fecal deposits can reach 1.5 pounds per day, per bird. The result is plants are no longer available to filter the water, while the masses of goose poo feed toxic algae blooms, furthering the chaos. Goose culls and habitat modification to discourage geese are often the only answer.
7. Mute Swan
Mute Swans are native to Europe and Asia but have been widely introduced worldwide. Known to have a nasty disposition when confronted, Mute Swans show up almost anywhere, where they compete with native migratory swans, disturb other waterfowl and plunder aquatic vegetation. They can also cause serious injuries to humans, should a conflict occur in a park, for instance. Wetlands home to a diversity of native species dependent on aquatic plants, such as pondweeds, may be stripped of vegetation almost entirely by roving Mute Swans. The combination of being powerful and voracious, with limited predation on adults, allows Mute Swans to inflict significant damage uninhibited. Furthermore, an invasive species often faces limited competition, while native species are ill-adapted to resist.
Why are Mute Swans in North America? Because of introductions that took place in the 1800s and 1900s that brought the birds from Europe and East Asia for ornamental purposes, only for the birds to escape and set up shop. Mute Swans are also dangerous, as shown by the drowning death of one unlucky Chicago man who was using the swans to control invasive geese.
The quintessential duck and the ancestor of the domestic farmyard duck, the Mallard is native to temperate and sub-tropical zones of North America, South America, Europe, Asia and Northern Africa. The ubiquitous waterbird has also been introduced to Australia, New Zealand, Southern South American countries and South Africa. The green headed males are the main culprits, for they aggressively mate with females of native dabbling ducks, leading to depletion of species of conservation concern. Furthermore, these more aggressive introduced ducks may outcompete native species for food, overgraze, and trigger water pollution. Mallards are also becoming a species of invasion and pathogen vector concern as carriers of avian influenza, and are considered a potential cause of a pandemics.
Native duck species that are at risk from Mallard hybridization and competition include the New Zealand Grey Duck, the Mottled Duck, the American Black Duck, the Hawaiian Duck, the African Black Duck, the Yellow-billed Duck, and the Meller’s Duck.
5. Rock Pigeon
Diseases, airplane strikes and displacement of native species are some of the results of massive congregations of Rock Pigeons, the species known as city pigeons or feral pigeons. In the United States alone, the birds cause a shocking $1.1 billion dollars in urban destruction annually, releasing droppings which contaminate urban areas and cause acid damage to buildings. Furthermore, the birds harm agriculture as grain intended for human consumption may be irreparably contaminated by pigeon flocks, which serve as reservoirs for some nasty avian diseases.
Rock Pigeons may carry Newcastle disease and ornithosis and spread salmonella, encephalitis, cryptoccosis, toxoplasmosis as well as hosting nasty parasites like fleas, mites and ticks, further affecting human health where the pigeons congregate. Methods of control include scaring, installation of baffles to prevent perching and nesting, killing by chemical means, shooting and trapping. Rock pigeons are also big enough to bring down planes if they get into the engine and, worse, commonly loiter at airports. The birds pose a threat of extinction to rare native species like the Galápagos Dove, carrying the disease Trichomonas gallinae, which can kill the scarce native birds as well as harming poultry stocks.
4. American Crow
Crows can devastate the environment when they get out of hand. While crows and their relatives are geniuses of the bird world and boast remarkable intelligence, their dexterity and intellectual capabilities, coupled with adaptability and aggression, spell trouble for many native species, farmers, and city dwellers alike. Roving groups of crows, known as murders, can spread avian diseases such as West Nile Virus while plundering crops in a relatively short timeframe. Crows are also capable at times of harming small or young livestock.
Human habitat modification has increased the number of crows, and increasing the ratio of edge habitat to interior habitat has allowed crows to raid bird nests (which otherwise would have been protected by deep forest) with ease. At the same time, habitat modifications that increase waste crops, and the presence of unsecured garbage and discarded food, may draw crows to congregate, allowing them increased access to prey. Despite their ability to, at times, inflict disproportionate damage, crows have a role in the ecosystem as sentinels and valuable scavengers. We just do not want to encourage them to excess.
3. Common Grackle
Native to North America, the Common Grackle is a large songbird that eats pretty much anything. Why would it become a problem? Human environmental modifications have increased feeding and nesting opportunities for the grackles, allowing them to conquer new territories and gain deeper access to natural areas where they can unleash a little havoc, eating other native birds and pillaging crops. While the grackles are technically songbirds, they are more like a half-baked imitation of a raptor in their roving hunts, eating birds, nestlings, small fish and amphibians as well as small mammals.
The birds may also dump large quantities of droppings in urban areas, steal food outside restaurants, attack patrons and even mob humans in groups when their nests are being guarded. Groups of grackles are often called a “plague” of grackles and may inflict significant damage when they feast on crops with little regard for efforts to discourage their onslaughts. Tame birds of prey, as well as chemical control, have been used to control the menace of grackle population growth and range expansion.
2. Red-billed Quelea
An avian agricultural pest on an unprecedented scale, the small, sparrow-like Red-billed Quelea has been aided on the African continent by human agricultural expansion, which in turn allows it to inflict greater damage due to its increased abundance and range. A member of the weaver family, this widely distributed African songbird is the single most abundant wild bird in the world, with a population of 1.5 billion. The methods of control often used against the species include fire bombing and chemical sprays, with the impact on agriculture being simply extraordinary. One has to witness the living clouds the birds create as they take off as a group to fully comprehend the huge numbers of such small birds.
Often called a “feathered locust,” the Red-billed Quelea is considered the most destructive bird on the planet for the threat it poses to human food security. The birds can reproduce at extraordinary rates thanks to their ability to produce three sets of young per year, with three each time around, for a potential yearly total of nine chicks.
1. Brown-headed Cowbird
North America’s proliferate answer to the Eurasian Cuckoo, the Brown-headed Cowbird evolved to lay its eggs in other bird’s nests. But the problem is not entirely natural. These birds once followed bison and thus could not take care of their young, leaving them behind in the care of other birds. When humans cleared land on a grand scale, cowbirds responded by increasing numbers and gaining new access to countless new bird populations. Now, they jeopardize the very survival of native bird species and are subject to culling programs to mitigate the threat.
Habitat modification, with hopes of reducing suitability of natural areas for cowbirds, is also used to protect native birds from the onslaught of these nest parasites. Shiny black with a brown head, the male cowbirds are subtly handsome, while the females are a drab brown color. Both genders are fairly secretive when it comes to breeding, avoiding being noticed by their victims. Once laid, the cowbird egg is incubated until it becomes a voracious eater that frequently causes the victim’s real young, its unfortunate nest mates, to starve. Species like the formerly endangered Kirtland’s Warbler are among the most vulnerable, having small populations and being too “naïve” to push the cowbird eggs out of their nest.