** Reply to note from Richard the Great -

<snip>

> It has always been and continues to be a mystery to me why these birds are so
> seldom seen there before about 5:30pm. Perhaps they are further offshore by
> day, feeding, resting, who knows what, then pack it up in the evening, come
> inshore 'til they hit the upwelling, then head north, thus I suspect when it
> comes to serious migration, they may be primarily nocturnal. I have no way of
> knowing this; maybe someone else has some thoughts. It is interesting to note
> Michael that you saw your Sabine's flocks in the morning hours around 8am.
> Nice posting Michael!

A couple of weather-related theories:

1) The N. Pacific High is responsible for the longshore winds along the
California coast which Richard mentions. It is also responsible for the
formation of a huge swath of sea stratus over the Northeast Pacific basin (Warm
air gets dragged up from the south flowing clockwise around the centre of the
high. Meeting progressively cooler water, the water vapor eventually condenses
out in the lower levels, gets trapped by the strong low level temperature
inversion under the high, and voila! - a huge deck of stratus and fog in the
east quadrants of the high pressure system). Once pushed onshore, the fog
usually burns back offshore with the heat of the sun (or more typically, with a
change to an offshore wind). Maximum heating of a California land surface in the
summer usually occurs around 1600-1700 hours, thus that is when one can expect
the least onshore penetration of fog. Perhaps the Sabine's Gulls are just taking
advantage of the diurnal fog burnoff to make seeing where they are going easier.

2) The past week or so, the fog banks have been tenacious and widespread along
the west coast north from California. Usually, the Sabine's travel north off the
west coast of Vancouver Island (sometimes at great distances offshore). Perhaps
the fog banks have been so thick that the gulls decided to take an inside
passage this week to avoid the low visibilities and give themselves a frame of
reference.

I will have to check the 1990 data to see if either of these scenarios applies.

- Jack


--------------
Jack Bowling
Prince George, BC
jbowling at direct.ca