Brown pelicans are the lumbering Paul Bunyans of the seabird world. The snaking arcs of their necks look almost prehistoric, and indeed, the earliest known pelican, dating back to over 30 million years ago, exhibits little to no change in fundamental morphology (Louchart, Tourment, Carrier 2011)!
As exclusively-oceanic predators, they have a bunch of cool sea-faring adaptations: specialized glands that allow them to drink salt water (Schmidt-Nielsen, Fange 1958), air sacs under their skin for added buoyancy (US Fish and Wildlife Service 2009), as well as a hunting technique that is novel amongst other Pelecaniids.
The brown pelican is unique in that it’s the only plunge-diving pelican species in existence (2009). While most others of its clade will scoop at fish while sitting at the water’s surface, brown pelicans dive-bomb the sea like war jets, tucking their wings behind them in one deadly thrust. The timing of this part is crucial. If they don’t corkscrew to the right by just the right amount, they could fatally injure their trachea and esophagus.
Assuming all goes well underwater, they flap their gums open. Their gular pouch balloons out like a 3-gallon net, ensnaring the hapless fish between their jaws: anchovies, sardines, herring, sheepshead, mullet, pigfish… Occasionally, they’ve even been seen gulping down crustaceans (2009).
These ambush strategies have proven fruitful in chasing the ever-fast and finicky epipelagic fish, but plummeting from heights of 60 ~ 70 feet is not a skill they are born with (2009). Before maturing into sleek, bow-winged adults, pelican youngsters look something like this:
It’s like an overcooked marshmallow tried to grow feathers (a 3-5 month old juvenile) – July 3, 2017. San Francisco, CA.
These little ones, while cute, are honestly terrible at fishing. I got the chance to see this particular one attempt a dive, during which it lost balance and smacked against the water in an explosive belly-flop! A 1969 paper, “Age and Hunting Success in the Brown Pelican (Pelicanus occidentalis)” by Gordon H. Orians, attests that plunge-diving is a technique that takes years to develop. Using a paired t-test of nearly 2000 observations off the coast of Playas del Coco, Costa Rica, Orians compared the catch rates amongst different life stages of brown pelicans, and found significant evidence that the learning period for the juvenile birds takes at least 18 months to 2 years (1969). Orians remarks that this phenomenon, if widespread, could in part explain why brown pelicans, as do many sea-faring bird species, exhibit an unusually delayed maturation (1969) – while juvenile brown pelicans fully fledge at about 3-5 months of age, they don’t reach sexual maturity until they’re about 3 years old (US Fish and Wildlife Service 2009).
Once they hit breeding age, their chocolatey manes melt away. Their lores and bill area flush with color, and their eyes metamorphose from deep brown to salty-pale.
As social birds, adult pelicans can often be seen soaring together in V-formation over the beaches of North and South America. There are lots of them diving off Santa Barbara and especially IV, so next time you see one of these bombardiering specialists, try and see if you could pick out the steps in its technique!
SOURCES:
Department of the Interior, U.S. Fish and Wildlife Service (2009). Brown Pelican [Fact sheet]
Retrieved from
https://www.fws.gov/home/feature/2009/pdf/brown_pelicanfactsheet09.pdf
Louchart, A. Tourment, N. Carrier, J. 2011. The earliest known pelican reveals 30 million years of evolutionary stasis in beak morphology. Journal of Ornithology, 152(1): 15-20.
Orians, G. H. 1969. Age and Hunting Success in the Brown Pelican (Pelecanus occidentalis). Animal Behavior, 17: 316-219.
Schmidt-Nielsen, K. Fange, R. 1958. The Function of the Salt Gland in the Brown Pelican. The Auk, 75(3): 282-289.
