It should also be noted that peak Snowy Owl densities are usually
in January, after Christmas Bird Count have come and gone. The
CBC data suffers from being too early to genuinely reflect every
Snowy Owl irruption (Leadbetter, Columbia Estuary and Tillamook
are all in mid-December). They do a fair job of of catching big
events though.

WAYNE WEBER wrote:
>
> Birders,
>
> In view of the appearance of one or more Snowy Owls at Salem, OR,
> about 8 places in WA, and in southwestern BC, I thought the attached
> message that I sent to INLAND-NW-BIRDERS a few days ago might be of
> interest.
>
> Mike Patterson's graph of wintering Snowy Owl numbers in WA and OR,
> accessible through a link in his Nov. 14 posting to TWEETERS and OBOL,
> is very useful in showing Snowy Owl flight years. However, it doesn't
> tell quite the whole story. The reason: in some years, Snowy Owl
> flights seem to virtually stop at the Canada-US border. The Ladner
> Christmas Bird Count, which covers much of the Fraser River delta, is
> a good barometer of Snowy Owl numbers. Since 1968, Snowy Owls have
> been missed on this count only 6 times, although most years, there are
> only 1 to 5 birds.
>
> The flight years, based on data from Ladner and nearby counts, have
> been 1966, 1970, 1973, 1977, 1980, 1984, 1992, and 1996, with no
> flight in 1988, but "echo flights" at least in 1971, 1974, 1978, and
> 1993. However, Mike's data show almost no Snowy Owls in 1970 (4 at
> Ladner, many others nearby), 1971 (11 at Ladner), 1978 (21 at Ladner),
> 1992 (13 at Ladner), or 1993 (13 at Ladner). It looks like few
> penetrated south of Ladner in those years.
>
> The peak CBC counts at Ladner were 107 (!) in 1973, 62 in 1996, and 40
> in 1984.
>
> Like Mike, I have long been intrigued by Christmas Bird Count data. (I
> served as compiler of the Vancouver CBC for 18 years between 1973 and
> 1994, and Western Canada CBC editor for American Birds from 1980
> through 1984.)
>
> At any rate, it looks like this will be a good Snowy Owl winter, so I
> hope lots of you have a chance to get out and enjoy these beautiful
> birds!
>
> Wayne C. Weber
> Kamloops and Delta, BC
> wayne_weber at bc.sympatico.ca
>
> -----Original Message-----
> From: WAYNE WEBER <WAYNE_WEBER at bc.sympatico.ca>
> To: CHARLES SWIFT <charless at moscow.com>; CRAIG CORDER
> <ccorder at eoni.com>; INLAND NW BIRDERS <inland-nw-birders at uidaho.edu>
> Date: Tuesday, November 07, 2000 12:46 PM
> Subject: SNOWY OWL FLIGHT YEARS IN THE PACIFIC NORTHWEST
>
> >Charles, Craig, and Inland Birders,
> >
> >Craig is correct that SNOWY OWL "flight years" in the Northwest do
> not
> >necessarily coincide with those east of the Rockies. To the best of
> my
> >knowledge, Snowy Owls wintering west of the Rockies come mainly from
> >breeding areas in Alaska. Lemming population "crashes" in Alaska may
> >or may not coincide with those in the central and eastern Arctic.
> >
> >Snowy Owl "flight years" in the Northwest occur quite predictably at
> >4-year intervals, or less frequently, at 3-year intervals. Since the
> >mid 1960s (my period of personal experience), major Snowy Owl flight
> >years in the Puget Sound-Gulf of Georgia area have been 1966, 1970,
> >1973, 1977, 1980, 1984, 1992, and 1996. (The 1988 "flight" failed
> >almost completely to materialize, for some reason.) Some of these
> >flight years have been followed by "echo flights" in the following
> >winter, in a few cases (1978, 1993) with numbers almost as high as in
> >the "flight" years, at least in some areas.
> >
> >The above summary is based largely on Christmas Bird Count numbers in
> >SW B.C. and NW Washington. I believe that "flight years" in E
> >Washington coincide with those west of the Cascades. I have not had
> >time to check CBC numbers from the Great Plains or Ontario, but I am
> >quite sure that the major flights are often in different winters than
> >those in the Northwest.
> >
> >If someone else has had time to check CBC data from east of the
> >Rockies, or recalls offhand which years were "flight years", please
> >enlighten us!
> >
> >At any rate, as 1996 was a major flight year, and we have never had a
> >gap of more than 4 years between irruptions (except for the "missed"
> >1988 flight), I fully expect (and hope) that 2000-2001 will be a big
> >Snowy Owl winter!
> >
> >Wayne C. Weber
> >Kamloops, BC
> >wayne_weber at bc.sympatico.ca
> >

--
Mike Patterson Alas, to wear the mantle of Galileo,
Astoria, OR it is not enough to be persecuted
celata at pacifier.com by an unkind establishment,
you must also be right.
---Robert Park
http://www.pacifier.com/~mpatters/bird/bird.html