Dear Stewart and all,

I consider the Eurasian Collared Dove to be an introduced species
because they were apparently brought to the Bahamas by mankind, from
which they spread throughout the United States from there. If they
hadn't been brought to the Bahamas in the first place, they probably
would not now be seen at all in our country.

On the other hand, there appears to be no evidence of the Cattle Egret
being brought to the U.S. by humans; therefore the Cattle Egret would
be a "self-introduced" bird, a phenomenon which I consider to be a
"natural" occurrence. The same could be said of the Barred Owl in the
Pacific Northwest.

Barry Ulman


On Nov 30, 2010, at 8:42 PM, Stewart Wechsler wrote:

> 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
>> ?
>
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