Hi Tweeters

>On July 28, Al Jaramillo said:
>
>> Yesterday I saw a juvenile Lesser Yellowlegs here in Half Moon Bay,
>>San Mateo Co, California. I looked up the early juvenile date in Dennis's
>>book and this one beats it by one day. Given that I am quite a bit further
>>south, it seems to be a pretty early record.
>
>And then Michael Price wrote:
>
>>In Vancouver BC, Deborah Kerr & Jim Morrison found couple of juv LEYE in
>>the Jericho Ponds yesterday the 27th (snip)
>>Vancouver BC average juv arrival of LEYE is July 25. I wonder sometimes if
>>they don't arrive from the west as a wave more or less simultaneously along
>>the coast.

Then Jack Bowling responded:

>Seeing as how Lesser Yellowlegs are *probably* breeding somewhere
>around the Prince George area (yet to be confirmed), it is amazing to
>annually witness the incredible buildup of young yellowlegs around the
>third week of July here. A favoured lakeshore can go from token
>numbers of locally produced young Greater Yellowlegs to scores of
>young Lessers within a few days. I think most of these are arriving
>from North of 60 on their way south. But likely a few are also finding
>their way in from the swamps near Prince George, too. I would find it
>hard to believe that a yellowlegs wave could originate from any
>quadrant other than the north in this part of the world.

But Interior migration routes would differ from coastal routes, and I'm sure
it gets more complicated when birds from the Interior move out to the coast,
which they may do at several or many locations. I *do* know from asking
people in the Fraser Valley to keep track of spring arrival dates that
arrivals on the inner coast here in Vancouver BC consistently are about a
week to two weeks earlier than even 50 km inland, and it seems to be the
same southbound, though the data's much sparser. The same discrepancy
obtains between Vancouver & Victoria BC, and I imagine that were arrival
dates in either direction monitored on the actual outer coast of BC, say in
Tofino, that they'd be even earlier. It's clear from Vancouver & Victoria BC
migrational data that birds migrate along the outer coast earlier than they
do the inner coast, and earlier along the Inner Coast than inland, with
about a week between each.

But, old weather guy, wouldn't many shorebirds from Alaskan populations be
able to stage at some location on the south or southwestern coast as they do
on your PG lakeshore, wait for a Pacific Low to come sweeping by, then ride
on the northwesterlies which come in behind the cold front, and hitchhike
down on those tailwinds? Landfall then becomes a matter of where the jet
stream pushes/pulls the Low to intersect the Coast.

What I'm trying to figure out is why shorebirds sometimes appear more or
less simultaneously along the Pacific Coast from Cascadia to California (I
say, that has a nice ring to it, doesn't it? "From Cascadia to California",
like the title of a National Geographic article of the 1950's), and it seems
that two possibilities are, first, that a big bunch set out from the north,
some drop out sequentially at various sites along the coast and the
strongest keep flying until they reach Al's region or further in a day or
two of sustained flight or, second, that they again leave en masse after
staging but use assisting winds associated with Pacific weather systems,
coming ashore wherever these systems do.

Michael Price
Vancouver BC Canada
michael_price at mindlink.bc.ca