Thursday, January 23, 2014

WHITE PELICAN—ANOTHER SUCCESS STORY


Just as happened with their cousins the Brown Pelicans, American White Pelican populations fluctuated greatly during the 20th Century. Having bred at Moses Lake and probably Sprague Lake in the interior of Washington early in the century, by the middle of it they had disappeared from the state as a breeding bird.

As the second half of the century crept along, these pelicans remained in the state as nonbreeding visitors, sometimes as many as hundreds of them at fish-rich lakes of the Columbia Basin. Oddly, there is no evidence that American White Pelicans suffered from DDT poisoning as did North American Brown Pelicans. So there must have been other reasons for a general decline in their populations, and human disturbance of breeding colonies is considered a very likely factor.


However, late in the century a turn-around was observed, and White Pelican populations began to increase all across the range of the species. In the 1990s, a few breeding colonies were discovered along the Columbia River in the Tri-Cities area. The primary one now is on Badger Island in McNary National Wildlife Refuge, where as many as 1,000 pairs have bred. An injured flightless Bald Eagle spent the summer of 2013 there, and the pelican population may have suffered from that.

In 2010, a small colony formed on Miller Sands Spit, in the Lower Columbia River, reaching a few hundred pairs by 2012. The Army Corp of Engineers covered the nesting area with dredge spoil that fall, but small numbers continued to be seen the next summer.

A great number of nonbreeding birds, up to a few thousand, occur in the state every summer along the Columbia River and some of its tributaries. It would have been unheard of to see White Pelicans in the Yakima River 20 years ago, but now they feed all along its length. Small numbers even spend the winter along the Lower Columbia River, something never observed before the last few years.


The species has increased all over the continent in recent years. Counts made in 1998-2001 totaled about twice as many birds as in 1979-1981. Those counts, now 15 years old, estimated over 150,000 birds, a respectable number of individuals for a very large bird such as this. And the estimate is conservative, as some known colonies were not surveyed. Further surveys are to be carried out.

Brown Pelicans and their close relative Peruvian Pelicans are both confined to the marine environment. They forage by flying, often in small flocks, well above the water surface and diving into it when prey are sighted. American White Pelicans, on the other hand, feed like other species of pelicans all over the world.

American White Pelicans spend much time on fresh water, although they are equally at home on salt water, and large numbers winter coastally. When foraging, several birds move through shallow water, dipping the bill in the water rapidly to capture nearby fish. Sometimes a whole line of birds forms and moves forward steadily, individuals dipping their bills one after another as they herd schools of fishes ahead of them.

Like gulls and other fish-eating birds, they also collect at dam spillways where their prey is delivered to them, often too stunned to escape. Dams are usually not good for fish but often good for birds!

Dennis Paulson

Wednesday, January 15, 2014

BROWN PELICANS IN WASHINGTON


When I moved to Washington in 1967, Brown Pelicans were rare in the state. Formerly common and widespread on all coasts of the US, their populations had crashed over a period of decades. Only after some time and much research did the cause become clear. Beginning soon after the Second World War, DDT was developed as the first of the modern synthetic pesticides. Within a short time, it had been liberally applied to crops all over the continent and to settled areas to combat the mosquitoes that transmitted diseases such as malaria.

DDT accumulates in tissues and becomes concentrated as it passes up the food chain. Fish picked it up from the water and passed it on to the pelicans that ate them, concentrating the chemical in pelicans more and more. One of its byproducts, DDE, interferes with calcium metabolism and as a consequence, the birds weren’t able to produce sufficient calcium for their eggshells. The thin-shelled eggs cracked when the adults attempted to incubate them, and reproductive success dropped precipitously all around our coasts.

The consequences of using this pesticide became so obvious that in 1972 the Environmental Protection Agency banned its use in the US. Fish took up less of it, eventually pelicans were pretty much free of it, and their nesting success improved greatly.

By the end of the 20th Century, Brown Pelicans had become common again on the Pacific coast and were coming up to Northwest waters in numbers never seen before. Now thousands of them visit our outer coast every summer to take advantage of fish populations apparently greater than those around their breeding grounds in southern California and Mexico. A small number of birds make their way all the way down to southern Puget Sound, and a few even stay through the winter now.

Our pelicans are a good mixture of adult birds with white heads and dark underparts and juveniles with brown heads and white underparts. They roost in large flocks on sand islands, jetties and piers and launch into the air to feed after long sessions of resting and preening.

This unmistakable bird is an aerial plunge diver. Single pelicans, sometimes in groups, fly several meters above the water and, when they spot a fish or school of fish below, they fold their wings and drop like a plummet, piercing the water with their long bill and almost completely submerging. When the bill reaches one or more fish, it opens and water rushes into the huge pouch. The pelican lifts its head and lets the water drain out, keeping the fish inside to be swallowed.


Heermann’s Gulls, breeding in the Gulf of California, also move north along the Pacific coast, becoming common in Washington waters while the pelicans are here and then moving south again in late fall.

When a pelican dives, it may be accompanied by one or more of these kleptoparasitic gulls. If a fish falls out of a pelican pouch, a gull is often there to grab it.

Dennis Paulson
Nature Blog Network