Monday, August 28, 2006

Birds from Elsewhere: What Do We Call Them?

Taking a cue from Jennifer Forman Orth of the Invasive Species Weblog, I did Google searches to determine the relative degree with which various terms are used to describe bird species that have been introduced to localities outside their native ranges. The results differ markedly from those reported by Forman Orth for invasive species in general (numbers reflect the number of hits for each term):
  • "exotic birds" (1,040,000)
  • "nuisance birds" (13,800)
  • "introduced birds" (12,900)
  • "non-native birds" (11,500)
  • "alien birds" (2,680)
  • "invasive birds" (755)
  • "non-indigenous birds" (233)
  • In recent years, the term "exotic" has come to be used interchangeably with invasive. In the bird world, however, it has long been used as term to describe birds in the pet trade. It therefore is not an appropriate search term to use in trying to locate documents on introduced or non-native birds.

    In reference to birds, "nuisance" has come to be used to describe any species that is causing economic damage to human interests. It is a term that can be applied to any bird species, regardless of its origins. It can even be applied to species protected in the U.S. by the Migratory Bird Treaty Act.

    In marked contrast to such organisms as insects and weeds, the terms "alien" and "invasive" have been applied sparingly (to date) to introduced or non-native birds. "Alien" is applicable in all cases, but "invasive" implies a sub-category of species that are harmful to human interests or ecosystem function.

    Although synonymous with introduced and non-native, the term "non-indigenous" has been applied sparingly (to date) in describing such populations of birds.

    Thus, the preferred search terms for locating Internet documents relating to bird species outside their native ranges appear to be "introduced" and/or "non-native."


    Blogger Jennifer Forman Orth said...

    Interesting stuff John.

    I was thinking about what the issue could be here. Is it just that few introduced bird species become what we might call "invasive"? Part of it has got to be that birds are loved by such a large segment of the population - even the much-maligned pigeon has its fans.

    Also I wonder how these definitions (or similar ones) apply in other countries.

    August 29, 2006 3:00 PM  
    Blogger John L. Trapp said...

    It seems to me that birds are often an afterthought on published lists of invasive species, even those of the U.S. Truth be told, however, although many bird species have been introduced into the U.S., few have been responsible for the types of economic and ecological damage as have other groups such as weeds, insects, and fish. Only a handful of birds introduced to the U.S. can truly be called invasive: European Starling, Rock Pigeon, and House Sparrow belong at the very top. I would also add Mute Swan, Eurasian Collared-Dove, and Monk Parakeet (talk about having a devoted following!).

    August 29, 2006 3:15 PM  
    Blogger Bill Pulliam said...

    I personally prefer "alien" for introduced birds in general, and "invasive" for those that expand their ranges and populations. So Eurasian Collared-Doves are "invasives," but European Goldfinches were just "aliens."

    August 30, 2006 6:55 PM  
    Blogger John L. Trapp said...

    Many species native to North America have expanded their ranges and populations without direct aid from humans. Examples of such species that I have seen some authors call "invasive" are Double-crested Cormorant and Brown-headed Cowbirds. But I believe that these examples represent a misuse of the term invasive. Personally, I reserve use of invasive for those species that (1) have been introduced to an area outside their normal range by direct human intervention, and (2) are causing economic or ecological damage. By that definition, I guess some populations of resident
    Canada Geese could be deemed invasive.

    August 30, 2006 8:53 PM  
    Blogger Bill Pulliam said...

    "Noxious avian weeds"

    August 30, 2006 9:42 PM  
    Blogger Jennifer Forman Orth said...

    ooo, I like that one!

    August 31, 2006 10:09 PM  
    Blogger Chris Kreussling (Flatbush Gardener) said...

    Gardening in Brooklyn, one of the epicenters of the Monk Parakeet invasions, I've had occasion to blog about them several times. The best descriptive phrase I've come up with so far is:

    "Brooklyn's most charismatic potentially invasive species"

    It's just not going to show up on a lot of Google searches.

    September 05, 2006 2:56 PM  

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