[APWG] Native "invaders"?

[Wayne Tyson]

John,

It's adaptation, not "invasion." When the context changes, by human agency 
or anything else, populations shift accordingly. Organisms and their 
environment are in a continuous process of change. Doves and rodents, for 
example, respond to increases in things like food supply (of course, it's 
more complex than that, but food and water are the big variables that affect 
most organisms.

I have concocted a "Law" of biology: "Organisms do what they can, when they 
can, where they can."

Discuss?

WT



----- Original Message ----- 
From: "John"
To: "john
Sent: Saturday, September 15, 2012 2:14 PM
Subject: [APWG] Native "invaders"?


> 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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