Hi Tweets

Scott Downes writes:

>Tweets,
>This afternoon was spent birding at Point no Point. DEspite the lack
>of numbers of Jaegers (might be too early) the rest of the birding
>was great,

Probably a titch early, Scott: in Vancouver BC, Parasitic Jaegers' average
southbound arrival date is Aug. 25 with the peak in Week 3 and Week 4 of
September. Whether it's going to be similar for an area as close as Point No
Point WA is open to study, as there doesn't seem to be much hard information
on how the jaeger migration actually works in the Inside Passage from
northern Vancouver Island on south to the western entrance to Strait of Juan
de Fuca.

When I first started seabirding, I thought Parasitic (PAJA) and other jaeger
species' migration was relatively simple: southbound jaegers at Vancouver BC
came into Georgia Strait at the N end of Vancouver Island and headed south
until they picked up a signal to turn W into Strait of Juan de Fuca and then
went out to the ocean. Northbound --well, I dunno. Probably the reverse. My
assumptions coincided with the local wisdom (which turned out to be the same
assumption, judging from the increasingly grumpy go-ask-your-mother
responses I'd get when I tried to find out definite, known facts on it from
the local gods). A hunch emerged that it is far more complex. When I saw the
typical jaeger counts at PNP posted on Tweeters, citing far higher numbers
at the same time of year, though not very distant from here, hunch became
certainty. So, how does it work?

Do the southbound jaegers we see come directly from the Pacific Ocean or
from Georgia Strait or both? If the former, they should enter Juan de Fuca
Strait from the Pacific and fan out among the various Gulf and San Juan
Islands, Puget Sound, and Georgia Strait (oddly, at Point Roberts WA, which
is part of the Greater Vancouver BC Checklist Area, virtually every jaeger,
north- and southbound, heads past the point from SE to NW; what the heck
could *that* mean?). Where then? Do they all funnel S into the S end of the
Sound and then head overland SW to the ocean, as Gene Hunn suggested once?
Or would some reverse and exit back through Juan de Fuca?

Or do some head down the Pacific coast, then enter northern Georgia Strait
at the Queen Charlotte entrance, head straight south down Georgia Strait and
then into Puget Sound and Juan de Fuca?

What role do choke points in straits play, such as Active Pass between Mayne
and Saturna Islands in the Gulf Islands, another virtually totally
unsurveyed site except for brief (10-15 minutes) runs through it on a BC
Ferry, with its enormous staging/early wintering flocks of tens of thousands
of terns and Bonaparte's Gulls? Do migrant jaegers stay longer at such
sites? Do they concentrate at them? Intuition says yes to both.

I'm curious about the numbers, too. During peak southbound migration, PAJA
numbers typically are 7-10 per day in Vancouver BC, yet at PNP they're far
greater (the first time I read a PNP account, I thought the writer had
typo'ed) though the site isn't a lot further south. I've wondered why ever
since. It'd be interesting, too, to see if there's an age-sorting; be easier
to tell with that more many birds. Is there a difference (i.e., age, sex,
breeding location) between birds which migrate through the Inside Passage
and those that migrate well out from land?

Michael Price
Vancouver BC Canada
mprice at mindlink.net