As in the two Baikal Teal records for Oregon. The Pochard in
Humboldt County has also been a target. Wonder if it's still
around.
Lars
On Feb 1, 2017, at 10:35 AM, Fred Lawrence Ramsey wrote:
#3 includes predation by humans.
On Feb 1, 2017, at 9:07 AM, Wayne Hoffman <whoffman@xxxxxxxx> wrote:
Hi -
I think in general, " the chances or odds that these birds will ever return
to their kind and resume living in their normal ranges" is generally low. A
good source of information on this subject is the Howell et al. field guide
to Rare Birds of North America (2014).
Several possibilities exist for the future of a seriously out-of-range bird,
most of them not very hopeful.
1. It is stuck in unsuitable habitat and perishes.
2. It finds the habitat acceptable and establishes a "new" migratory
pattern rather than returning to its origin. This has been documented with
some frequency in waterfowl. For example, the Falcated Duck that wintered
near Eugene for 3 consecutive winters probably did not go back to Asia each
summer. An Eurasian "Common" Teal drake has wintered for a few years on a
particular pond near Toledo. The past two years the pond has also had a
couple of wintering hybrid Common X Green-winged Teal. We assume that the
Eurasian has mated with a hen Green-winged Teal and migrates with it, within
North America; an example of the Stephen Stills effect (when you're not with
the one you love..."
3. It is predated by a local predator. There is a body of research from
the 1970s indicating that raptors look for odd or unfamiliar prey. If a hawk
or falcon flushes a flock of birds it tends to preferentially chase
individuals that in one way or another are distinctive within the group.
This makes sense because sometimes a bird flying a bit differently is
injured and easier to catch, but it also means the raptor is likely to
choose to chase the vagrant.
4. It becomes resident in the area it strayed to, and remains, perhaps for
years. I know of several examples among geese. Another is the Steller's
Sea Eagle that appeared at Taku River SE of Juneau Alaska and remained for
10+ years. The multiple Jackdaws that appeared in the northeast US and
Canada in the 1980s tended to take up residence and remain, in some cases
for years.
and finally, 5. It may be he vanguard of a range expansion. Natural range
expansions are almost always driven by conditions and population dynamics in
the source areas. In the 1970s Barred Owls started showing up in British
Columbia, the northern Rockies, and hen the Pacific Northwest, and have
since become common. High nesting success in source areas together with
habitat changes (increased riparian forest and shelter belts providing a
"bridge" across the northern Great Plains) apparently allowed a considerable
number of colonists into the northwest.
Wayne
On 1/31/2017 9:59:58 PM, Jimhardman <jhardman43@xxxxxxxxx> wrote:
I have a question that I would like to have the birding experts ponder, and
it is this: With all the rare birds that we have been seeing this winter
i.e. - the Florence Brambling, Portland’s Black Throated Blue and others,
What are the chances or odds that these birds will ever return to their
kind and resume living in their normal ranges? POST: Send your post to
obol@xxxxxxxxxxxxx
JOIN OR QUIT: //www.freelists.org/list/obol ;
OBOL archives: www.freelists.org/archive/obol
Contact moderator: obol-moderators@xxxxxxxxxxxxx
