Subject: Re: Cause and effect (was Bayswater Beach...)
Date: Nov 4 12:21:35 1996
From: jcbowling at mindlink.bc.ca - jcbowling at mindlink.bc.ca


Michael P. wondered:

> Following from the second, one of those 'Well, duh!'-type realisations
>hit. I've always wondered not only from what part of the Cascadian outer
>coast these WEGU and hybrids arise, but what prompts them to come here
>and when. Unless, I'm mistaking effect for cause here, their arrival here
>inland is coincident with the outer coast getting creamed by the first
>big Pacific Lows which move S from the Gulf of Alaska when the Jet Stream
>loops S in mid- or late October. So, if many of our wintering diving
>ducks ride out from the Interior to the coast on the first continental
>Arctic High irruptions, the reverse arrival of these gulls heading inland
>from the coast depends on the timing of the first winter storms.

Possible for the gulls for big winds. However, I am looking at pictures of
10 ad., one 2nd winter, and one 1st-winter Glaucous-winged Gulls I took
Nov. 26, 1983 at 48.4N, 148.3W. This is 700 nautical miles south of the
nearest landfall, the Shumagin Is. off the southern Alaska Peninsula (they
are not *all* garbage dump birds). The wind at that time was relatively
light for the n.e. Pacific in November at SW 25 knots. The gulls showed no
sign of stress, especially since they just perched on the superstructure of
the ship whenever they needed a rest. What's my point? There are likely
significant numbers of gulls out on the open ocean in the non-breeding
season when adults move away from the breeding colonies and join the
younger ones. Therefore, you can expect that any storm moving onshore will
intercept these gulls and potentially blow them onshore. However, this
likely only occurs with winds of storm or hurricane force since any lighter
winds are no problem for gulls. Note that, given a choice, ships deviate
from a planned route whenever a big storm lies in their path. This would
mean there would be fewer ships on which gulls could perch to take refuge
from big winds, so they may not have much choice other than to be blown
with the wind inland. As for the scoters, etc., I believe the main impetus
for the southward migration of the Arctic breeding waterfowl is the
southward progression of lake freezeup, which can lag the first southward
arrival of Arctic air by a week or two depending on residency time of the
Arctic air.

>Oh yeah, apparently there's been a vole population crash this year, and
>according to the Glabe & Mail bird column, they're netting large (20-30
>per night at one site, another place had a hundred)numbers of Boreal Owls
>in Eastern Canada, and there's every expectation that Northern Hawk-Owls
>are heading S too. If the crash is across the board, we may be seeing
>more than usual numbers of Snowy, Great Gray, and Hawk Owls--maybe even
>Boreals-- here too; they do seem to have arrived a week or two early this
>year. Are there any night-netting sites here in Cascadia where a
>comparison may be made?

A N. Hawk Owl already turned up here in P.G. about a week ago. Pretty
early. By the way, the Arctic has not really been all that cold yet this
year so low rodent numbers is a more plausible factor than weather in the
recent appearance of Arctic and sub-Arctic raptors. Don't know about
night-netting sites. Perhaps Dennis P. would know?

- Jack






Jack Bowling
Prince George, BC
Canada
jcbowling at mindlink.bc.ca