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.
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.