[obol] Re: Coos Gyr, lotsa Cacklers 10/18/2014
- From: Wayne Hoffman <whoffman@xxxxxxxx>
- To: Tim Rodenkirk <timrodenkirk@xxxxxxxxx>
- Date: Tue, 21 Oct 2014 11:42:24 -0700
Hi -
Dave is correct that most raptors follow migratory routes mostly over
land. Many have great unwillingness to cross water, and some seem to
suffer mortality on even modest crossings. From my years in the Florida
Keys, I have a lot of experience with raptors travelling down the Keys in
fall, and then certain species retracing their course back to the
mainland. Turkey Vultures, Swainson's Hawks, Broad-winged Hawks, and
Short-tailed Hawks in particular were often seen making these return
trips. At that time Swainson's and Short-tails were unknown in Cuba, just
90 miles to the south, even though both species were regular moving up and
down the Keys. I also heard several accounts from boaters of finding
multiple "hawks" floating dead on the water off the keys during the period
of fall migration. We were never able to find out which species, or
determine causes of death, but evidently for some species, ocean crossings
were very difficult or risky.
This does not apply to Peregrine Falcons, however, as they are well-known
to regularly make long over-water flights. Merlins also seemed very
willing to head out over the ocean. Ospreys and Swallow-tailed Kites also
regularly migrate south out of Florida toward Cuba and the Yucatan
Peninsula. I don't think we know enough about Gyrfalcon movements to be
able to say how willing they are to make long ocean crossings. I suspect
they are physiologically capable of flying directly from SW Alaska to
Oregon or northern California. I doubt they regularly try to kill geese
over the ocean, as I imagine they would have difficulty feeding on them at
sea, particularly if the surface was at all rough.
So, the possibility of following geese south remains speculative. The most
likely alternative explanation for the regular occurrence of Gyrfalcons
with geese in SW Oregon/NW California is that individuals that made it into
that area over land encountered the geese, and made a habit of returning in
subsequent years. I do not know whether we know ages on many of the fall
birds down here, but if many are adults, return migration would be
supported. The fall concentrations of Cackling Geese in those areas is a
recent development, so however the Gyrs are getting there, it probably is
recent as well.
Wayne
On Tue, Oct 21, 2014 at 4:57 AM, Tim Rodenkirk <timrodenkirk@xxxxxxxxx>
wrote:
> The migration route difference makes sense Dave, I wonder how the Gyr(s)
> find the cacklers? There has been a Gyr or several Gyrs that show up where
> the Aleutian cacklers are for the past decade or so. The Gyr reports have
> followed the cacklers south into CA some years also if I remember correctly.
>
> Tim R
> Coos Bay
>
> On Mon, Oct 20, 2014 at 11:40 PM, David Irons <llsdirons@xxxxxxx> wrote:
>
>> Alan et al.,
>>
>> I suspect that the apparent connection between the arrival of Aleutian
>> Cackling Geese and the earliest Gyrfalcons of the season in Coos County is
>> temporal only and that it has little to do with the route each species took
>> to get here. As a general rule, raptors are diurnal migrants whose
>> migratory routes are mostly over land, which allows them to take advantage
>> of thermal uplift that occurs during daylight hours. Aleutian Cackling
>> Geese take a more direct route from their Arctic breeding grounds, which
>> takes them across well over a thousand miles of open ocean. When migrating,
>> geese to continue flying all day and all night, making a mostly non-stop
>> flight. When hunting waterfowl, falcons essentially blast their prey to the
>> ground with a high-speed stoop from above. I can't imagine a falcon, even a
>> Gyr grabbing a goose out of midair or carrying one very far after knocking
>> it down into the water. With no terra firma on which to dine, what point
>> would there be to the falcons following their prey base out over the open
>> ocean?
>>
>> Dave Irons
>> Portland, OR
>>
>> ------------------------------
>> Subject: [obol] Re: Coos Gyr, lotsa Cacklers 10/18/2014
>> From: acontrer56@xxxxxxxxx
>> Date: Mon, 20 Oct 2014 15:06:26 -0700
>> CC: obol@xxxxxxxxxxxxx
>> To: timrodenkirk@xxxxxxxxx
>>
>>
>> There has been a pattern of occasional October Gyrs on the south coast.
>> I wonder if they simply fly down with the geese. Why not?
>> .
>> .
>> Alan Contreras
>> acontrer56@xxxxxxxxx
>>
>> Eugene, Oregon
>>
>>
>>
>>
>> On Oct 20, 2014, at 3:01 PM, Tim Rodenkirk wrote:
>>
>> Jim Heaney observed a GYRFALCON at New River, Coos this past weekend (on
>> Saturday). I remember when Dave Pitkin was still alive, that he observed a
>> Gyrhanging with the ALEUTIAN CACKLING GEESE in that same area for a few
>> falls and perhaps followed the flocks down from Alaska. I was with Terry
>> Wahl on Sunday (the 19th) and he got a call from Rick McKenzie who has a
>> large ranch near New Lake in the same area where the Gyr was seen. Rick
>> said he had 20,000 Aleutians on his ranch, a pretty huge number for fall
>> (perhaps the most he has had on his place this time of year?).
>>
>> Jim mentioned seeing the Gyr carrying a gull but also saw evidence of
>> cackler kills along the beach there...
>>
>> Merry migration!
>> Tim R
>> Coos Bay
>>
>>
>>
>
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