[APWG] Native "invaders"?
John
jmbarr at academicplanet.com
Sat Sep 15 16:14:58 CDT 2012
Is there a word or phrase for those species that might be native, but
because of their adaptability to humans and human actions, might be
considered invasive species?
I am not interested in rehashing the definition of invasive species,
these are all native pre-human history. The negative impact on humans
or the environment is lacking in some cases and clear in others. I am
looking for another word or phrase to indicate those species whose
population growth is directly tied to human action.
I know that, in general, armadillo are not considered invasive species
because they invaded under their own power without an assist by humans.
In the Austin area, I can think of several bird species that were
native to the area, but whose populations have exploded because of
human's impacts on the environment.
They are:
White Winged Doves
Boat-tailed Grackles
Cliff swallows
Blue Jays
Purple Martins (I hesitate to include this popular bird, however......)
Brown headed cowbirds
The White Winged Doves used to be rare to endangered, then they
learned to nest outside of South Texas thorny scrub and to visit
backyard bird feeders. They have moved steadily north from south
Texas to Dallas over the past 20 years displacing other dove species.
Boat-tailed Grackles love to congregate in urban areas at night and
forage in the surrounding suburban and rural areas during the day
looking for bugs and grubs stirred up by tractors and lawnmowers.
Cliff Swallows have expanded their range and numbers by using highway
underpasses.
Blue Jays are one of the most problematic. They follow the
encroachment of suburban sprawl especially backyard bird feeders, then
eliminate or displace the less aggressive Scrub Jays. Blue Jays are
nest robbers, and one of the predators on our endangered Golden
Cheeked Warbler and Black Capped Vireos.
Purple Martins nest almost exclusively in human built houses.
Brown headed cow birds have become year round residents because their
natural affiliation with migratory Bison has been replaced by
perennial cattle herds in fenced pastures.
Any thoughts?
john in Austin
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