Written By: Sarah Girton
It is an unfortunate reality that human activity has caused the accidental or intentional relocation of thousands of species across the planet. Rarely, those species end up finding their own niche in the local ecosystem, but more often they wreak havoc on the environment. Some notable examples are the Brown Tree Snake in Guam, and the Burmese Pythons in the Florida Everglades. Additionally, there are hundreds of species of birds around the world who have found themselves living in non-native areas.
Today we are going to highlight a few of the invasive bird species in North America; Not to demonize them or ostracize them, because it is through no fault of their own that they ended up here. They are simply trying to survive like anyone else.
We will learn about how they came to this continent, their life history, and how they have affected their new ecosystems. Below are short passages about 4 such birds that have established populations in this country and even into Canada and Central America.
A staple of cities and suburbs the world over, the Rock Dove has a bit of a reputation as a nuisance. Some people refer to them as “rats with wings”, and consider them dirty. But there is actually a lot to appreciate about this bird’s relationship with humans.
Rock doves came to North America in the early 17th century on board European ships. They have a long history of assisting humans, and are actually one of the earliest domesticated animals, with records going back at least 5,000 years! They have been trained by humans to perform a variety of tasks; most notably delivering messages. Some pigeons have even earned medals for their services during wartime!
Aside from their relationships with humans, one must take time to appreciate their beauty. They are so common that they are often overlooked. Their green and purple iridescence, the rich slate and gray coloring in their feathers. Each bird has unique patterns in their plumage, which is uncommon in a lot of bird species.
Unfortunately, Rock Doves do compete with a lot of native bird species for food and nesting sites.
Eurasian Collared Dove
The Eurasian Collared Dove is a much more recent resident of the United States, having only been here since the 1970s, when around 50 escaped captivity in the Bahamas. After arriving in Florida, they quickly spread around the whole continent. Now they can be found pretty much everywhere including suburbs, cities, towns, plains…pretty much anywhere with a human presence. They are frequenters of bird feeders, though they can sometimes chase off smaller birds. It’s so endearing to me that mated pairs will often perch on my fence and engage in mutual preening, which strengthens the pair bond. It’s a similar behavior to humans holding hands or stroking a loved one’s hair; quite the romantic little birds!
On a less than happy note, they have a tendency to drive off the native and much smaller Mourning Doves, as they compete for nesting spots and food sources. One bit of good news with this is that in the places they’ve been established the longest, such as Florida, their populations are starting to decline, suggesting that their negative effects on local bird populations may start to decline as well.
House Sparrows were intentionally released in New York City to combat the local linden moth population, and it worked…but the House Sparrows also began to enjoy the local crops and other food sources for local birds.
So how has the House Sparrow affected indigenous bird species? They are very aggressive little birds and are known to evict other birds from desirable nesting sites. They are also not terribly picky with what they eat, inconveniencing a variety of other bird species.
They are considered an agricultural pest, causing huge monetary and seed inventory losses.
If you’ve noticed the black “bibs” on the males, you’re seeing the hierarchical markers that the males use to sort out social status. The bigger and darker the bib, the higher up the male is in the pecking order. Younger, lower ranking males will move out of the way for those males at food sources, and females tend to choose those males as mates.
Whether this bird grinds your gears or not, you have to admit that they are stunning! Their spotted iridescent feathers are truly a work of art, and their eyeliner is on point. But this is another introduced bird species that has been wreaking havoc on both the environment and economy. They have a tendency to swarm in the hundreds or thousands, and back in the 1960s one of these swarms actually caused a massive plane crash, killing 62 people.
There are 114 species of Starlings, with most being tropic dwelling species. They are excellent mimics, which is what Shakespeare alluded to in his play Henry IV in the quote, “Nay, I’ll have a starling shall be taught to speak nothing but Mortimer, and give it to him to keep his anger still in motion.” This is most probably why Starlings were brought to the US.
Like the other bird species I’ve mentioned so far, this bird is very competitive and aggressive, especially with food sources and nesting cavities. Bluebirds are one of the birds most affected by this.
What I’ve discussed today are human-caused threats to local ecosystems and economies. I personally do not hold grudges against any animal for living where it shouldn’t. The animal had no say in where it was born, or where it was transported to. Rock Doves, House Sparrows, Collared Doves, European Starlings, and the thousands of other plant and animal species that have been forcefully uprooted from their homes and plopped into unfamiliar environments are just trying to survive like anyone else. They have a powerful biological drive to eat and to produce offspring, even at the expense of indigenous species.
That being said, there is scientifically-backed legislation in place for managing invasive species. There are things you can do to discourage invasive species, but killing them is still illegal, as it breaks animal welfare laws.
This situation is unfortunate for everyone involved, but going forward there are always things we can do to minimize the impact of invasive birds. The Nature Conservancy has compiled a helpful list. Their best advice? Prevent invasive species in the first place. You can read the whole article on their website here.