---------- Forwarded message ---------
From: Nancy Stotz <nstotznew@xxxxxxxxx>
Date: Sun, Mar 12, 2023 at 2:28 PM
Subject: [obol] Scoter flocks foraging on herring eggs (long)
To: obol <obol@xxxxxxxxxxxxx>
Yesterday, my husband and I decided to take advantage of a rare dry day and
run over to Newport, hoping to see some of the herring spawn action. Our
first indication that anything special was happening was the thousands of
gulls loafing on the beach north of the jetty at Yaquina Bay SP (vs the
dozens to hundreds we more normally encounter there). Mid-day, a little
after low tide, there were also many hundreds of gulls in the shallow
water just below the north side of the Hwy 101 bridge. Lots of scoters were
across the way, by the south jetty, but while we were on the north shore,
they all took off and disappeared out into the ocean. By the time we swung
by the south jetty mid-afternoon, the scoters were back, and they were
doing their synchronized diving thing. I was totally enthralled by this
behavior when we got to see it in 2020 (OBOL post about that encounter
available here:
https://www.freelists.org/post/obol/Synchronized-scoters ;), so we found a
couple flat rocks and settled in for the show. A link to two videos from
this year follows the description below.
Tight masses of scoters, mostly in long, semi-triangular formations, were
milling about in the channel; eventually a front group would angle toward
the jetty, stringing out the triangle behind them. Closer to the jetty, the
leading birds would dive, immediately followed by trailing scoters, one
after another, as more distant scoters flew in to join the feed line. We
eventually learned to recognize a smooth patch of water that would appear
after about 30 seconds, which showed us approximately where the scoters
were going to surface. Birds would begin to pop up, just a few at first,
and then suddenly a whole mass, frantically scrabbling about and quickly
moving farther out from the jetty. Though it was tough to watch individual
birds in the swarming mass as they surfaced, sometimes we managed to see a
chunk of what looked like 'seaweed' (a gummy, pale green, semi-leafy mass)
being manipulated in a scoter's bill. The group would reform out in the
channel, and begin their organized march toward the jetty again.
When I posted about this in 2020, Wayne Hoffman let me know that they are
feeding on herring eggs (which are sticky and adhere to rocks and submerged
vegetation), and the synchronized diving and surfacing are thought to be a
tactic to reduce the risk of predation (Birds of Oregon says the same).
Watching the frantic scrambling after they surface, and the ever-present
gulls that immediately congregate around surfacing swarms, made us wonder
about it being an anti-theft tactic as well. It would seem like the tight
masses of scoters, going every which way, might make it tougher for a
kleptoparasitic gull to focus on an individual scoter to grab an egg (or
chunk of vegetation with eggs attached).
Two videos from this year are posted via the link below. Though there's an
unfortunate amount of traffic noise (we weren't the only ones to take
advantage of a beautiful Saturday!), if you turn your volume up, you can
hear the cool, hollow "wappa wappa wappa" noise their wings make when they
fly.
https://www.flickr.com/gp/98973699@N03/6m7hB95co0
Many thanks to those who posted to OBOL about the herring spawns occurring
this year so we knew it was time to get over there.
Nancy Stotz
Corvallis
