Dive Dry with Dr. Bill

#374: A Cormorant Convention

It has been nearly three months since I last took a plunge into mother Ocean. That will be remedied the next two weekends as the ladies of LSD (Laguna Sea Dwellers, one of my favorite dive clubs) are coming over to dive with Dr. Bill, then the following weekend is our annual Avalon Harbor Clean-Up. Despite the "drought," I haven't remained entirely dry. Thanks to a neighbor who hired a very poor contractor nine years ago, my house has plenty of leaks and small waterfalls. But I digress... as usual.

On a recent non-diving weekend I took advantage of nice weather to film what appeared to be a convention of cormorants in the vicinity of Avalon Bay. There were thousands of them congregating in the dive park and even entering Avalon Bay. I'd say billions of them, but that would be a fish... er, bird... story. I am by no means a bird enthusiast, but cormorants seem to have good intentions at least while submerged. I've filmed plenty of them as they hunt underwater for various fish and invertebrates. However, as Paul Harvey said, to present "the rest of the story" I needed a fair bit of topside footage as well. I enjoyed two days of sunshine, dive friends at the park and a chance to film "the birds" (not, fortunately, ala Alfred Hitchcock).

When I got home, I resorted to my Audubon field guides and determined that most of them were probably Brandt's cormorants (Phalacrocorax penicillatus). These birds are known from southern British Columbia, Canada, to Baja California, Mexico. Now as a scientist, I can't simply enjoy the wonders of Nature without asking a few questions. It's in our nature to do that. Why were all these birds gathering here? I knew the SCICo was interested in drawing more convention business here, but guessed these visitors had nothing to do with their marketing efforts! I noticed several bait balls which could certainly explain the bird's presence... after all, a free meal will get my attention any time! You know, girls... the way to a man's heart is through his esophagus (or is it stomach)?

I was astounded at the number of birds that seemed to be doing repeated dives in the vicinity of the baitballs. However, as the raft of dark bodies entered the harbor, I had a chance to observe them more closely. Although I watched many birds diving, I saw no evidence of fishing or feeding at all. Hmmm. Then another hypothesis entered my brain. Perhaps these were males showing off their diving prowess to the ladies, and this was a gathering for one of the two or three most important functions of any species... mating.

I noted that several of the birds had nice white tufts of feathers on the side of their head. I surmised that these were the males. However, when I did my research, I discovered that these were not indicative of maleness as either gender could possess them early in the breeding season. Since I saw relatively few birds with them, I researched further. A cobalt blue throat pouch is present only during the breeding season, but it is hard to see... especially if you forgot your glasses. Fortunately there is a secondary characteristic indicating it is time for reproduction, and I did see many of the birds with a buff colored patch on either side of the pouch.

Adult Brandt's cormorants are almost 36" high, making them a pretty big bird... although no match for the one on Sesame Street. They are dark in color with hints of iridescence, which I detected as greenish and bluish in color. This species nests on coastal and offshore rocks adjacent to the waters in which they feed. Three to six chalky bluish eggs may be found in the nests which are made from seaweed, plants or items stolen from the nests of seagulls. I guess that makes them cormorant kleptos! Immature birds are dark brown with lighter chests and were easy to distinguish within the group, especially after they dried off in the sun.

I would have loved to be underwater with the incredible number of cormorants diving. Several who were said they were seeing dozens underwater at a time. However, I thoroughly enjoyed watching them in the warmth of the sun and filming their topside behavior. Like the anhingas I see near Mom's house in Florida, cormorants spread their wings out to dry in the sun. While preening, I had seen Brandt's cormorants rubbing their heads against their feathers. However, I knew they lack an oil gland to keep their feathers waterproof like many other seabirds. Most seemed to spend a lot of time fluffing and adjusting their feathers, so I assumed many were female (duck and hide). I even noticed one rather aggressive cormorant pecking at other birds on a rock it had just climbed out on... he (I presume) chased at least three other birds away, including one which was trying to get out of the water itself.

For someone who knows so little about birds, I learned a lot through my filming and quick research on the Brandt's cormorant. Some times even I have to "dive dry" in my work. When I focus on the marine birds episode for my proposed cable TV show "Munching and Mating in the Macrocystis," I'll do a lot more research on them and share it with you. I hope you, too, have learned a bit about these birds that swim... and that it has whetted (or should I say wetted!) your appetite for more. I'm off to give a talk on "the night shift" at the Orange County Underwater Photographic Society... I hope I can continue to stay dry with these rains. At least I won't be under the waterfall at home.

© 2010 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Head of Brandt's cormorant, some attendees of the convention just inside the dive park;
cormorant preening itself (alternate caption: "Am I a boy... or a girl?")
and cormorant holding wings out to dry.

This document maintained by Dr. Bill Bushing.
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