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Dive Dry with Dr. Bill

#375: A Problem With The "Pterodactyls"

Back in the late 1960s when I moved to Catalina to begin teaching marine biology, one of the major environmental issues in our region's waters was the demise of the brown pelican (Pelecanus occidentalis). Scientists formed hypotheses about why these marine birds were possibly following their look-alikes, the prehistoric pterodactyls, to extinction. The answer was industrial pollution. DDT and its breakdown products, released by Montrose Chemical, were being dumped in sewage streams off White's Point on the mainland.

The DDT became biomagnified as it moved up the food chain through plankton, then baitfish and finally predatory fish until the levels ingested by pelicans were sufficient to affect their reproduction. The DDT and other chemicals interfered with the biochemical processes necessary to produce their eggs. The shells on the eggs laid by the females were too thin, and cracked when the mother sat on the nest to incubate them. A similar mechanism also affected bald eagles, driving both species to endangered status.

Fortunately, new environmental laws such as the Federal Water Pollution Control Act of 1972 mandated treatment of waste water dumped into the ocean, and further constraints were levied against industrial pollution. When I worked briefly as a pollution control engineer for Northrop Corporation in the late 1970s, I had to ensure our facility's compliance with such regulations. A lawsuit against Montrose Chemical provided some remediation money to assist in the recovery of the bald eagle. Fortunately our brown pelicans also recovered.

This winter another threat has left hundreds of brown pelicans dead or starving. As many as 1,000 birds failed to migrate south from the Pacific Northwest and ended up in shelters further north. For the last two years thousands of pelicans have remained off Oregon rather than make the migration to California waters. Based on counts by the Audubon Society dating back to 1918, fewer than 100 birds remained in Oregon for the winter historically. The past two years over 3,000 have been counted. The ones that did arrive in our State's waters were battered by the recent series of strong storms. Many of them have ended up in rehabilitation centers along our coast. I'm sure a number of my readers have seen the pelican population at Avalon's Cabrillo Mole, begging food from the anglers who fish off the jetty there.

The estimated pelican population in North and Central America has increased to about 650,000 birds. It was only last November that the brown pelican was removed from the endangered species list. During their recovery, the summer range has extended as far north as British Columbia. Now some might be quick to suggest that climate change has caused this, as could be the case, but it is too early to tell. Some scientists believe the pelicans remained in the Northwest due to an extended period of upwelling that brought nutrient rich waters to the surface there, enhancing productivity and creating more food. For some reason, this suddenly reversed itself in January resulting in a diminished food supply up north.

Other scientists point to shorter term weather phenomena rather than global climate change as the cause. Although they are ocean hunters, pelicans are unable to feed during periods of rough water and high winds that accompany storms. If El Nino is already affecting our regional weather patterns as some suggest, this could be part of the puzzle. If pelicans are grounded (and not in the good sense) by strong winds, within 3-4 days they may be too weak to venture out to capture food.

Another possible hypothesis is based on normal population dynamics for any species. Critters which can't produce their own food, rely on the supply given them by Mother Nature. We did so in our hunting and gathering days, but became much less dependent on wild sources once we adopted agriculture and raised animals for food. Of course ultimately even these depend on the natural systems since fertile soil and animal feed supplements are part of the picture.

When the brown pelican population rebounded to its current high levels, it may have outstripped the natural food supply. Of course intensive fishing by humans has diminished the stocks of many potential food sources, so the resource base for the pelicans may be substantially less than it was 50-60 years ago. When resources are scarce and population numbers are high, something has to give. Starvation is one unfortunate mechanism through which Mother Nature adjusts the balance in ecosystems. Our own human population is rapidly outstripping its natural resources as well... fortunately I am far from starvation.

© 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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Pelican diving and capturing fish in its bill in better days; brown pelican at rest and preening its feathers.

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia