CAPITAL
CORMORANT CAPABILITIES
Wing drying and expandable throat pouches
Photo by Dr. Dan Sudia. Used with permission. Copyright 2004.
These poses always grab my attention -- hold it for a pleasurable while: cormorants atop pilings, piers, whatever -- extending their wings -- necks, heads, long hooked bills uplifted - uptilted -- in their uniquely regal manner. Are they simply hanging themselves out to dry and pompously showing off, or is there a bit more to it?
Many of us have observed that cormorants are great underwater swimmers. (Had a great view of one from above in the Anacortes marine area.) We are aware they are able to slip easily through kelp and eelgrass beds. I've read thay can dive downward more than 100 feet.
Relatively heavy-boned water birds, their air sacks are minimal and their outer feathers, unlike most aquatic birds, are very wettable -- very un-waterproof -- all factors which decrease bouyancy and make for this great and efficient underwater locomotion. Furthermore they are able to squeeze air from feathers which allows them to even more easily sink and remain beneath the water.
So we see their feathers are invaluable aids to one of their primary endeavors: the underwater pursuit of fish meals -- generally small fish. In this mode they hold their wings slightly extended from the sides of their bodies and move forward with the help of their webbed feet.
But there apparently is, in addition, an insulating layer of air retained in place next to their bodies. Hence they can spend a relatively long period of time seeking prey in water which at times is quite chilly.
We could surmise that cormorants have it both ways: comfy body air-wraps, yet marvelous and extensive underwater adaptations and capabilities.
But their underwater forays also leave cormorants' outer feathers dripping wet -- completely sodden. Hence the unfurled wing routine - a fairly lengthy one, time-wise, to assist in the their drying.
Another reason which was suggested in the past for cormorant wing extention was body temperature regulation. And although plausable sounding, it has not been accepted by many authoratative personages. Wing drying has however.
Yet another capability we may not give a great deal of thought to when viewing cormorants are their throat pouches. Yes, they assist in species identification, but these expandable receptacles possess other pluses -- also bring cormorants into close relationship with pelicans -- all-be-it pelican pouches are considerably larger.
The most widespread cormorant in North America, the Double-Crested Cormorants' pouches are yellow-orange -- brighter during breeding season when they play a role in courtship rituals. And these stretchable sacks enable them to take in multi fish as well as store eats for nestlings.
I have read that decades ago Japanese fishermen leashed together a half dozen Double-Cresteds, each with a fitted neck-ring to temporarily prevent swallowing: then sent them forth to capture fish. The productive fisher-birds were then later brought in and their throat bags emptied of captured prey. Would have to admit it was a very imaginative technique -- way to fish -- based on cormorant observation and noting that they were good fishers: but doubtful the cormorants were pleased with being removed from their natural habitat and working in servitude.
The Chinese, it seems, used cormorants as fishers as well, allowing a bird to keep each 7th fish caught -- using the latter as a motivational tool.
Cormorant pouches are also used as a natural means of cooling - "cormorant conditioning". They simply flutter the sack's bare skin -- fan it -- an especially fine adaption when incubating eggs or cooling nestlings on a warm day.
And last but certainly not least we're back to the pleasure factor - the pure pleasure we derive from seeing Double Crested Cormorants -- other cormorant species as well -- spreading out those dark wings and hanging them out to dry -- yes, letting it all hang out with that cormorant air of nonchalant hoity-toityness.
Pat Nash
Beach Watcher
Class of '94