For those interested, some statistics on Seattle Accipiters:
I have been asked to chime in with some basic stats from my 9 year
(2002-2011) color-banding study looking at winter site-fidelity of these two
species and, since 2004, the nesting ecology of Cooper's in Seattle. Please
also see the mentioned Dennis Paulson Blog at Slater Mus. and Ruth Taylor's
posting to tweeters.
Over this time period, I have color banded equal numbers of "wintering"
Cooper's(COHA) and Sharpies(SSHA) at my in-city back yard banding station
(23 each). This is from random banding attempts - no set time or frequency
schedule. Individuals of both species have demonstrated winter- to- winter
site fidelity over 3 or more successive winters. However, in other areas of
the city, on fairly regular banding forays, it has been more difficult to
observe and band SSHA than COHA. Both species are regularly present in the
winter; I have no hard figures on relative numbers of the two species.
Regular, extensive but not exhaustive nesting surveys(within city limits)
have been done since 2005 with small, steady increases in nesting attempts
observed each year; 26 attempts in 2011. About 80% of the nests are
successful to fledging. High percentage of nests are in wooded parks (very
small to large) and creek drainages, or in hillside green spaces; a few have
been in residential areas. Total COHA nests 2004-2011 is 112 which have
produced 269 fledglings. The sightings reports indicate that most of the
COHAs remain somewhat local with outliers ranging from southern BC in the
north to as far south as Lake Tahoe.
Some nests have been close to the central downtown core ( on the north and
east perimeters). In addition, I have had sightings reports of the color
banded birds of both species throughout the downtown core; Lower Queen
Anne/Uptown, Belltown, along the water front, Downtown library, First Hill,
Capitol Hill, etc. (See Ruth Taylor's comments). Also, I have done
rescues(both species) from inside all manner of building types/locations
throughout the city over this same time period.
No SSHA nesting attempts have been observed over this same time period.
Therefore, SSHA likely only winter visitors to the city (See Dennis
Paulson's comments).
I think it is fair to say that in winter time, without the time or
opportunity to determine the specific species, "an accipiter" would suffice,
knowing that it could just as well be a Coops or a Sharpie. And, separating
the two can be troublesome/tricky at times without the observation of key
details.
See http://www.wos.org/research.html for details on observing and reporting
these and other color banded birds to me or others.


Jack Bettesworth