What would be probabilities for a dark chocolate brown raptor, same size or
slightly larger that a raven that was chasing it? I saw it Sunday, March 26,
2006, at the base of the Snoqualmie Pass ski resort, about 1:30 in the
afternoon.

My immediate impression by shape was falcon, although not as angular as a
Merlin or Peregrine. Nevertheless, it had broadly pointed wingtips, and a
not-too-long narrow (not fan-shaped) tail.

Initially I saw it for about five seconds, as it flew towards me and then
turned perpendicular to me about fifty to seventy-five yards away, at or
slightly above eyelevel. The wing beats were deep, powerful, and slow. It
disappeared behind some evergreens, but appeared again a minute or so later on
reverse course, still being closely chased by a raven, with other ravens
observing. It was cloudy, not snowing at the time although there were flurries
throughout the day. The lighting gave a pretty decent view all things considered,
although I didn't have any binoculars.

The uniform dark brown color contrasted clearly with the black raven. There
appeared to be no barring, streaking, or mottling, although as it flew out
of sight I perhaps imagined a flash of a light white patch out towards the
primaries.

The Sibley Guide to Birds says a raven is 2.6 lbs, wingspan 53", length 24".
Wheeler & Clark's Photographic Guide says a Gyrfalcon is 2.2 to 4.6 lbs
(average 3.1), wingspan 43-51" (47), length 19-24" (22). The Northern Goshawk
female is 26-43 oz (37), wingspan 41-45" (43), length 18-20" (19).

Although I would not ordinarily think to confuse a falcon with an accipiter,
all the guides indicate the Gyr has a longer tail and more rounded wings
than most falcons, and the Gos has longer wings and shorter tail than a Cooper's.

The closest dark chocolate brown depiction in any of my field guides is
Sibley's dark adult Gyr (page 132), but Sibley indicates the dark morphs
primarily are in Labrador. The National Geographic shows a dark brown morph juvenile
which has a uniformly brown back, but it appears the front is much lighter
(and only after seeing this bird did I notice it indicates a juvenile Gos can
be confused with a Gyr). The guides show a juvenile Gos as brown, but most
seem to be a lighter shade than the bird I saw. The Nat Geo shows a juvenile
Gos with a darker shade of brown, but with faint white barring and a more
mottled appearance. Whatever white I saw was not a clear bar, but more an
imagined lighter patch.

I didn't see any barring of any kind on the tail, although I don't recall
having an angle which would let me see any barring. I didn't see any white
undertail coverts, which I would have expected to see on a Goshawk when it flew
perpendicular to me.

The terrain was mostly open, with the bird flying on the far side of a row
of evergreens, although there are lots of trees in the general area.

I'm leaning towards Gyr, but wondering how common dark brown morphs are
around here. My guess is mostly because my initial impression was falcon rather
than accipiter, and because the terrain was mostly open.

Any suggestions on how one tells a Gyr from a Gos, where one doesn't get a
chance to study color and/or head patterns?

Thanks,

Eric Stahlfeld
Burien, Washington