Peter Burke and I saw the gyrfalcon this morning on the big poles w of Taft on
Trilby about 10am. After maybe 20 minutes, the bird flew off in pursuit of
something toward the sw corner of the landfill and appeared to land on the
ground but we lost sight of it. About an hour later another big falcon landed
on a pole east of the one the gyr had been on. Eventually the second bird
moved one pole to the west and perched on the same pole the gyr had chosen
earlier (I am guessing the 5th big pole w of Taft). The second bird proved to
be a prairie falcon. Interestingly, we actually saw the prairie fly n to
pursue a common raven that was heading s out of the landfill with a big
mouthful of something distinctly yellow. What could the prize have been? The
falcon tried to shake down the raven but we did not see anything drop. This
episode was very reminiscent of what jaegers do with gulls.
Gauging the size of birds is tough on those big poles. Obviously, if the
choice is between gyr and prairie and one sees the underwing pattern, an ID is
rather simple. Back in the comfort of 70-degree computer chairs, Peter and I
went to school on our photos and would now suggest the following:
Both gyr and prairie are big gray falcons.
Both have dark malars, with a typical prairie falcon having a darker and
narrower malar than this gyr.
Both have bright white throats.
Both have pale areas on the side of the face behind the malar. On the prairie,
this area matches the throat in whiteness. On the gyr it is bigger and grayer
than the throat, not nearly as contrasting.
The prairie has a small white patch immediately behind the eye, the gyr does
not.
The supercilium of the prairie shows some bright white, the gyr's is pale but
not bright white.
Cere of prairie seems brighter yellow than the pale yellow-green of gyr.
As anyone who has seen this gyr knows, if it is on a pole, it may not, probably
won't, stay put for long. As soon as getting on a big gray falcon, check the
head. If it has bright white anywhere other than the throat, it is likely a
prairie.
We are trying to be helpful here and in no way quibble with anyone who has
wrestled with an ID of the falcons in this situation. The guides do not say
enough of help with this difficult ID challenge. One would think, myself
included, there would be little confusion between birds 6 inches different in
length and with one being twice the weight of the other. Not true at the
distances involved, being puffed up in cold weather, having full crops/bellies
and being under the optical illusion those monster poles seem to generate. See
my poor photos attached that, nevertheless, mirror the views one gets in terms
of distance and lighting. Left bird is gyr, right is prairie.
[cid:a3ff8f63-acb3-46ad-8da7-a10fd87655e7]
[cid:badbcb4b-1c51-4ff6-aad9-07229b387a0d]
And thank you to Andy Bankert and Robert Beauchamp for first finding the
gyrfalcon last winter and this winter, respectively.
Dave Leatherman
Fort Collins
--
You received this message because you are subscribed to the Google Groups
"Colorado Birds" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/cobirds/CY4PR0601MB360341315D06D4E495738261C1100%40CY4PR0601MB3603.namprd06.prod.outlook.com.
