Tweets,

If a species arrives in a new area on its own it may be inappropriate to
refer to it as "introduced", but it would still be what I call a
"successful new immigrant species". Either way it is likely to disturb
the order and balance of the existing community of plant, animal and,
fungal species. This community of native species has what I have
started calling the "three co's". They are co-evolved, co-adapted and
co-dependent. Since the last "co" has another meaning in psychology one
could alternately call that "interdependent". When any successful new
immigrant species becomes established in its new home it is likely to
drive the species it eats and competes with into greater rarity or
extirpation. It will then cause indirect problems for any species that
was best adapted to life with any species that has declined or could
become an indirect benefit for species negatively impacted by a species
that has declined. On the whole it can be expected to create
difficulties for a chain of species that are not well adapted to the new
mix of species in the changed community.

-Stewart

Stewart Wechsler
Nature Walks/Adventures
Local Native Plant Expert
West Seattle
206 932-7225



On 11:59 AM, Eugene and Nancy Hunn wrote:
>
> Evan, tweets,
>
> I believe it is also the case the Eurasian Collared-Dove greatly
> expanded its European range in the past few decades from the eastern
> Mediterranean now all the way to Scotland and perhaps beyond. I like
> to entertain the possibility that this explosive expansion of range
> could well have brought collared-doves across the Atlantic on their
> own, as apparently was the case with the Cattle Egret. In that case
> they would not be an "introduced" species.
>
> Gene Hunn
>
> Sonoma, CA
>
> enhunn323 at comcast.net
>
> *From:* tweeters-bounces at mailman2.u.washington.edu
> [mailto:tweeters-bounces at mailman2.u.washington.edu] *On Behalf Of
> *Evan Houston
> *Sent:* Monday, November 29, 2010 1:26 PM
> *To:* Tweeters
> *Subject:* [Tweeters] Eurasian Collared-Dove spread!
>
> Hi Tweeters,
>
> Today I came across a very interesting post by a bird blogger that
> illustrates the rather amazing spread of Eurasian Collared-Doves
> across North America during the past couple of decades. This blogger
> has used data from the bird sightings database eBird.org to create a
> year-by-year animation that illustrates the rapid westward and
> northward spread of this species. The animation shows an amazing
> spread of green (the blog explains that green indicates presence of
> the species being depicted) through the 2000s.
>
> link (click on animated gif within this link to see the animation):
>
> http://bbill.blogspot.com/2010/11/ebird-visualizations-eurasian-collared.html
>
> From the book "Birds of Washington" by Wahl, Tweit, and Mlodinow,
> collared-doves apparently became established first in the Bahamas
> during the early 1970s due to escapes and releases, and have been
> spreading across North America ever since, with the first record for
> WA being in 2000.
>
> One thing to keep in mind is that the number of users of eBird is also
> increasing over time, so with fewer total sightings entered the longer
> you go back, absence of a species from a given area will not be as
> reliable. This increase in users over time might tend to make the
> spread look a bit faster than it really was, but nevertheless the
> trend of spreading rapidly to the west and north spread is undeniable.
>
> The final point of this post is that using eBird to submit your
> sightings can really contribute to very interesting research on bird
> distribution!
>
> Good birding,
>
> Evan Houston
>
> Seattle, WA
>