Here in the South Okanagan we hear a great deal about invasive plants (weeds) and rightly so as the economic and environmental costs of these plants are significant. What we don’t hear about quite so often are invasive animals, even though North America in general and the South Okanagan in particular are now home to numerous alien invaders. Many, but not all, of these invaders have significant associated economic and environmental costs.
Some of the better known invasive species are European starlings, zebra mussels, bullfrogs and carp. Starlings arrived in North America (Central Park, New York City) in 1890 as part of an individual’s plan to introduce to the U.S. all of the birds mentioned in the works of Shakespeare. What an incredibly costly decision that was. Starlings compete with native birds such as bluebirds and flickers for nesting sites and cause significant economic damage to crops, including our own cherries and grapes. The annual economic cost in the U.S. is estimated to exceed $500 million in crop damage alone. In addition, they can cause significant structural damage with their corrosive droppings.
The common carp, native to Asia but introduced in the U.S. in the early 1800s, was first noted in the Okanagan in 1912. It is now found in many lakes and rivers in southern B.C. While it is a popular food fish in parts of Asia, it is highly detrimental to lakes in southern B.C., causing increased water turbidity and significant algal blooms. Its feeding habits are highly disruptive to many duck populations and it eats vast quantities of insects and fish eggs which would normally be food for native species.
Another very recently arrived alien in the South Okanagan is the Eurasian collared dove. This bird, about the size and weight of a city pigeon (itself an alien species in North America), has spread across North America faster than any other known bird species and has had a similar story in Europe. In the late 1890s this bird was found only in central, warm-temperate Asia. However, beginning in the 20th century it has made a remarkable advance across Europe. Climate seems to be no barrier as it is now found north of the Arctic Circle.
The Eurasian collared dove was introduced to the Bahamas in the 1970s (we just never learn!) and by 1982 had spread to Florida. As late as 2000 it was still mostly confined to the East and Gulf coasts of the U.S. with sporadic sightings elsewhere. However, since then there has been a veritable explosion in the population of this dove. In the early part of the 2000s it was consistently found in the Cawston area but in the last few years has rapidly expanded northward. This past summer breeding pairs were noted in Kaleden as well as elsewhere in southern B.C. So in less than 30 years this alien has effectively colonized all of North America.
Unlike most stories of alien species in North America, which generally range from bad news to really bad news, so far there appears to be few detrimental effects associated with the invasion of the Eurasian collared dove. These doves do best in altered habitats — rural to semi-urban areas with some farms and/or feed lots. The observational data indicates they do not seem to compete with the native mourning dove, which is the only widespread native dove in North America. Let us hope this continues to be the case.
The South Okanagan Naturalists’ Club meets monthly at the Penticton United Church on Main Street at 7:30 p.m. Our Nov. 24 speaker is Karilyn Long, fisheries biologist with the Okanagan Nation Alliance, who will talk about her work to protect and restore salmon resources and their habitat in the Okanagan Valley.
Robert Handfield is past-president of the South Okanagan