Are some birds invasive species?
Many nature lovers know that plants such as European Common Reed (or Phragmites), Dog-strangling Vine, Russian Olive, and buckthorn are non-native invasive plants that are unwelcome because they crowd out native species that are important parts of healthy biodiverse habitats. The Norway Maple is an example of a non-native tree and the Zebra Mussel is an invasive non-native species of mollusc. Is it possible that some Southwestern Ontario’s birds are non-native species? The answer is yes.
Mute Swan, European Starling, House Sparrow, and Rock Pigeon are examples of the non-native bird species that are here in numbers.
The first records of Mute Swans in Canada are from the 1870s. They were brought here by European settlers as decorative waterfowl and they have since thrived. The population in this lower Great Lakes region of Ontario is one of the largest. Mute Swans can be very aggressive. They will frequently outcompete other birds for habitat. Although Mute Swans are widely admired, they will at times attack people.
Numbers of Mute Swans have grown a lot though the last four decades. The Environment and Climate Change Canada website states that “unless control measures are expanded, these trends will likely continue until the population occupies all available habitat. Increased numbers and distribution will increase the risks that this species poses to Canada’s native wildlife, wetland habitats and people.”
Mute Swans are admired by many for their romantic beauty, however this non-native species is an avian bully that outcompetes many native birds for habitat.
All photos by Paul Nicholson.
Like the Mute Swan, the Rock Pigeon is an invasive bird species that has its own beauty. Unlike the Mute Swan however, Rock Pigeons are generally reviled. They have thrived in urban settings such as downtown London because they are an adaptive synanthropic species. These birds don’t crowd out other bird species aggressively. They are simply exploiting a niche. Populations are kept in check by raptors such as the Peregrine Falcon. Like some other invasive bird species, Pigeons have adapted so successfully to new environments that many don’t even migrate.
The Pigeon (above) which is part of the dove family and the House Sparrow (below) are non-native bird species that have adapted exceedingly well to built environments such as cities.
House Sparrows are native to Europe and the Middle East. After having been introduced in New York City in 1851, the species spread across most of North America. The bird is now one of the most populous in Ontario and it is the most widely distributed bird on the planet. The House Sparrow is another synanthrope: You will not find the bird outside of built environments. They are problematic because they aggressively outcompete native bird species such as Purple Martins for nesting habitat. As cavity nesters, they prefer nest sites such as nest boxes and holes in trees and fence posts.
As its name suggests, the European Starling hails from Europe. It was another cavity-nesting species that was introduced in the 1800s in New York City and has since flourished. Because of this bird’s tenacity, diverse appetites, and adaptability to built environments, it too has become one of Ontario’s and North America’s most numerous birds.
Although the Starling’s plumage does have its own beauty, many people overlook this aspect of the bird. Interestingly, the online Global Invasive Species Database includes Starlings in its “100 of the World's Worst Invasive Alien Species” list, adding that they “contribute to the decline of local native bird species through competition for resources and nesting spaces.”
European Starlings (above) are native to Europe, not North America. They arrived from England in New York City in the late 1800s and have since flourished. Large flocks of Starlings (below) are known as murmurations.
The story of the Eurasian Collared-Dove is an interesting one. A few of these birds are seen each year in Southwestern Ontario and birders are often pleased to add a sighting of this species to their list. There was one just outside of Rondeau Provincial Park through the spring.
This Dove, however, is a non-native bird. Some escaped from a pet shop in the Bahamas in 1974. By 1982 some birds had flown to Florida where a viable population was established. Since that time, their range has expanded rapidly, first to the west and then then to the north. The Cornell Lab of Ornithology’s Project FeederWatch blog has an animated graphic that shows the rapid range change of the Eurasian Collared-Dove from 2000 to 2009. The same blog entry states that “no species of bird has colonized North America at the speed with which the Eurasian Collared-Dove has marched across the continent.”
There are few effective measures that allow us to directly check the population explosions of invasive bird species.