From the Field: Unexpected River Visitors
From the Field: By Sarah Sinn-White, Expedition Leader
White pelicans are not an animal typically thought of when one imagines the wildlife of the Columbia River. Considered a littoral seabird, or a bird found along ocean shorelines, this prehistoric-looking bird is a semi-regular sighting during our travels down the river system that separates Washington and Oregon. With a wingspan than can be over 10 feet, rivaling the albatross, this bird displays an incredible sky silhouette as their “squadrons” fly overhead, catching gusts and updrafts. They come to the Columbia River and its tributary rivers for nesting, migrations and summer time feeding. Just like our guests aboard the Wilderness Legacy, this is a destination for them.
Typically gregarious, these strikingly colored birds gather in groups, especially during the summer. Working together to feed opportunistically on small fish, as a flock they herd schooling fish towards the shore or circle around them for easier feeding. White Pelicans then dip forward like an over-grown dabbling duck to scoop fish into their pouched bills. These extendable gular sacks are so large the White Pelican can hold roughly 3 gallons of water within that pouch. This pouch also contains a large amount of blood vessels near the surface, allowing for a cooling effect when the pouch is flapped upwards, similar to a desert jackrabbit moving its ears to catch the slightest breeze.
When rearing offspring large amounts of fish must be provided to the chicks at the nesting sites. Typically, a single chick needs roughly 150 pounds of food to reach a size large enough to fledge. In order to provide this large volume, the adults will switch from day to night foraging techniques. Although hunting by sight is more difficult during these dark hours it allows the adults to take advantage of the vertical diel migration layer of biomass that comes to the surface at crepuscular, twilight hours. This migration layer that occurs across the globe, is the largest migration in the world, also contains a wider diversity of species and larger fish than what the mature pelicans forage up during the day, allowing them to feed their chicks with fewer but bigger fish. Occasionally within these nesting colonies the parents can be opportunistic kleptoparasites on each other, essentially stealing the hard work of another parent right out of the bill and feeding it their own offspring instead. This behavior can also carry over to other species the White Pelican interacts with, such as our Double Crested Cormorants that also forage throughout the Columbia River corridor. Letting the Cormorants dive and swim beneath the surface, driving feeder fish upwards with their efforts, then the paddling, dabbling Pelicans simply scoop up the now-available prey from shallower depths.
Using technique, skill and talent the White Pelicans have made a presence for themselves within the Columbia River and its riparian ecosystem. Working together to feed, feeding off each other, and gathering in their colorful groups of white, orange and spots of black, they are a sight to see in their aloft v-formations or simply floating along the river as we float right beside.