First off, best of the season to everyone!
I
captured this amazing footage yesterday.
These surf scoters, a kind of duck wintering here on the west
coast, show interesting clustering patterns. They align direction and increase
density as they travel between feeding locations. At feeding locations they spread out and
dive in various directions for food.
When their feeding opportunities are exhausted in one area, they increase
density again, align in a common direction, and high-tail it, so to speak, to
the next good feeding area. It seems to me
these alignment and density changes are clear phase transitions, and
the high density clusters (when they are aligned in direction) appear to involve
a wake-following/hydrodynamic mechanism to optimize travel time and energy
expenditure. They generally travel at
angles to each other, and not directly behind.
After capturing this
video yesterday on a relatively poor camera, I decided to buy a better HDD
camera today and a monopod, for some better footage today. While a
technical camera glitch means I have no additional footage from today, much to
my chagrin, I did see some fantastic formations of a much larger flock of
scoters (perhaps 1000), including an arc formation in which they fan out in
a curve of one bird beside each other, perhaps acting something like a net,
covering as much area as possible in search of food. I also saw tell-tale
signs of a convection pattern whereby following birds, in what I surmise to
be zones of lower energy expenditure, pass leading birds in zones
of higher energy expenditure, creating a rotational pattern. This is the sort of
convection dynamic,very apparent in bicycle pelotons, that I have so
much wanted to document in natural collectives. It was unfortunate that I
ended up with no additional footage today, but it looks like I will get some
more opportunities, as the birds are likely to be around for a while.
While there are published papers discussing scoter
migratory and foraging patterns, from what I could see there are no published
papers discussing in detail these fascinating clustering
formations.
Hugh Trenchard
Victoria, BC
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