Nocturnal Migrants, Cont.
Last night I wrote that, from my home in Arroyo Grande, I had been counting
the migrants seen crossing the moon. The 55 birds seen between 9:19 PM and
12:01 AM showed that last night was a flight night. I haven't done the
math--as if I could--to get an idea of how many birds were actually in the
sky over AG last night, but it had to be a lot.
I awoke at 5:30AM and stumbled to the front deck with my scope. In fifteen
minutes I had 4 passerines cross the moon in the pre-dawn gloom. Things were
still moving. As some of you know, when there's an east or northeast wind
in the morning in spring I often see migrants in numbers flying by to the
north from the front deck in the first few hours of morning. The east wind
blows nocturnal migrants westward, increasing our numbers locally--and I
believe they are using the contours of the land to protect them from the
wind as they continue to work their way north after dawn.
It was still this morning. Between 6:35 and 7:35 AM I had a very modest
count of northward-moving birds from the front deck: 38 swallows (3 Cliffs,
the rest Trees), 25 Tricolored Blackbirds (2 flocks), 12 warblers (4
Yellow-rumps, the rest distant), 3 Am. Goldfinches, and 2 hummingbirds
(zipping straight north above the trees). If we had had an east wind in the
morning, after a flight night, the count would have been much higher, and
probably more diverse, at this date.
Last night I speculated that we could have lots of migrants in SLOCo this
morning--unless the birds overflew us and kept going. This seems to be what
happened. Birding a few local spots in south county this morning where I
normally encounter migrants I found none, zero, el zilcho that were
unequivocally migrants. Not one Yellow-rump, Townsend's, flycatcher
concentration or the like.
We have often wondered, on mornings like this, if birds weren't moving, if
they weren't stopping here, or if they simply were dispersed so broadly as
to be invisible. Last night was clearly a decent flight night. But they
seemed to have kept going. Maybe, because the weather grounded them in
Southern California within a few hundred miles south, they vast majority
passed over us by early morning and came down well to the north? Some were
still in the air at dawn, but I saw no evidence of them "on the ground".