I spent Friday morning, Jan 31, working the area from Pt Gray to
Spanish Banks and beyond, the south shore of Burrard Inlet, in
Vancouver BC, looking for the Common Eider. I found it, but in
doing so, observed some fantastic scoter behaviour.

Standard scoter behaviour, when in large groups, involves then
floating around together for a while, then a group dive, in
which a fairly constant number of scoters dive, until all are
down.

In searching for the eider, I worked west from Spanish Banks
along the shore line, about 1 mile, trying to get a better look
at a very large number of scoters. I have no idea how many birds
there were (did M Price estimate 10,000 last week?), but there
were lots of them. They were constantly moving about, in groups,
flying a distance of a few hundred yards to up to perhaps a half
a mile, then all landing in about the same area, again forming a
very dense raft.

>From my location, as little as 100 yards away, it looked like
there was a scoter every square foot in these dense rafts.
Since I was at water level, this estimate of 1 bird per square
foot is at best a guess. If accurate, it can be used to estimate
the number of birds, since these rafts were as much as 200 yards
long by perhaps 30 yards. There wer 3 or 4 such rafts. Even if
there was only 1 scoter per square yard, this is still up to
24,000 birds.

Anyway, getting back to scoter behaviour. Once the raft
reformed, the birds appeared to be very active, while on the
surface. They seemed to be paddling very hard, while not moving
very much. It could be that there was a strong tide, but it
looked like they were stamping their feet. The water was
churning. Not frothing, but very active. After a minute or two
on the surface, the group dive would begin at one end and work
to the other end. Gradually, the entire group of birds would
all be down.

All three species of scoter were represented: perhaps 85% surf,
10% black, 5% white winged.

Of the surf scoters, almost all the birds were breeding plumage
males and first years males, perhaps as much as 90% adults.
There were more male black scoters than females, but the ratio
may have been 70/30. Almost all the white winged scoters were
adult males. There were very small numbers of other birds,
amouting in total to no more than 2 or 3% of the total: greater
scaups (M and F), red breasted mergansers, a some first years
gulls.

Given the high numbers of adult males of all three species, it
occurred to me that this might represent pre-mating behaviour.
The way the birds were moving, it appeared that their hormones
were surging.

Terres, Audubon Encyclopedia, suggests scoters eat shelled
critters almost exclusively. The Birds of BC says they are
known to eat herring. Given this, perhaps the churned up
appearence of the water was the caused by the herring. The
rapid movement of a large group from one place to another
corresponds then to the scoters moving from one herring
upwelling to another, not some hormonally triggered frenzy.

The common eider was with about 40 first year surf scoters.
This may account for the presence of the bird down here: he got
in with the wrong company and lost his way. I noticed it while
scanning the raft, only because the first year birds were
together, a little closer to shore (50 yards), out of the mass
of birds. They stayed there for about 10 minutes, apparently
resting and trying to digest their last food, with the eider on
the outside edge of this small grouo, then they all flew back
into the middle of the raft and the eider effectively
disappeared, although only 100 yards from shore.

It is a male first year bird. If the bill colour holds, it is a
member of the western v-nigra subspecies. There is no black on
the bird yet, just the white on the breast and around the neck,
the rest being more or less light brown (some white spotting on
the back). It is clearly larger than the scoters, perhaps 25%.
When flying away, the rear tail area exhibited a spiky
appearance, like a punk hairdo, but that was perhaps just
because it had its flaps down, in preparation for landing.

All this and sunny. Quite a morning.

Brent

--
Brent Beach, Victoria, BC, CA