Egrets, Efforts, and Energy

by Rex Burress

The morning hours were getting into the swing of a hot day down by the riverside. Resting in the comfort of a shaded bench, I saw a Great Egret flap by with determined wing strokes as if it knew where it was going.

Trailing behind the egret were two Black-crowned Night-Herons, also seemingly headed for some objective. Maybe it was the Great Wading Bird Rendezvous.

I wondered about what they knew. Was it some special pool along the river where fishing was good? I know down-river there is an egret rookery in the cottonwoods towering above a marsh. Some of that coming and going is probably connected to nesting operations in the springtime.

I watched that egret fly by so buoyantly, head tucked over its back like it was resting while the wing motors propelled the body steadily onward. It resembled some giant butterfly in lightness of motion, and there was no comparison with the way the cormorant had flashed by with head pointed forward like some dive bomber on a mission. Its wings were rapidly beating without any pretense at artistry.

The egret seemed to portray the essence of energy conservation. The fuel to sustain that flight was culled from living things around the waterway. Fish, frogs, and small aquatic life have to be caught and then converted into energy.

The egrets that build nests on Lake Merritt's Duck Islands have established some remarkable sites in spite of being in the middle of a city. Over and over again, we see how providing habitat space for wild animals is all they need to thrive. Habitat and protection. They will find the food source and craft their nest sites if they have a place.

It all started at Lake Merritt in 1972 when a few Black-crowned Night-Herons established the first nests on the manmade islands that just then were supporting tall trees and dense brush. The Great Egrets and the Snowy Egrets followed. The larger Great Egrets took advantage of the higher trees to build their stick nests, and the snowies and the night-herons sought out the dense shrubbery of the bottlebrush. By 1980 they were flourishing even as multitudes of joggers and park visitors watched from the shoreline. Some watched, but it was amazing how many people zoomed right on past, some never realizing what a fascinating activity was being enacted  - the greatest show in Oakland!  with no admission fee.

When the eggs hatched, the parent egrets solved the food problem by commuting out to the San Francisco Bay shoreline and catching baitfish. Burdened with a payload, they came gracefully gliding back to the lake, and regurgitated a fishy meal for the eager egret infants.

They seemed to go one parent at a time, slowly flapping into the sky, above the freeway traffic and above the skyscrapers, with the thought of gathering food firmly embedded in their minds. There is conservation of energy even when an egret stalks the fish. First the eye contact, then the slow footsteps toward the quarry, and at last the coiled strike, usually made in successful contact. For a bird that nests in trees, all of their foraging is spent on the ground.

In year 2000, Double-crested Cormorants took a fancy to the egret nesting tree - and the egret nest platforms - and built a dozen nests in the causarina tree. Next year, forty-plus cormorants had forced most of the egrets out of their turf. Those black birds are not the easy flyer like the egret, but power their way forward with rapidly beating wings.

Cormorants are more efficient in the water, as they are propelled along on strong legs, parting the water like a submarine. Researchers report that their bones are denser and heavier than most birds, and they do not have water-repellent feathers. Less buoyancy allows them to slip through the water easier, but they have to dry their bodies in the sun and air after fishing ... and fly faster to keep aloft!

The shifting focus of the egret tree brings to mind the reality of nature coursing along naturally, the more aggressive gaining an edge in the competition for shelter and food. But is it desirable that cormorants have displaced the egrets and forced them to seek other sites? A few egrets moved over to the less-desirable pine tree, but many have simply left the lake.

Are there too many cormorants? Full protection has allowed them to become quite numerous, not only at Lake Merritt and along the coast, but they are making intrusions into the trees at local lakes, and as far inland as the Feather River Rookery near Oroville, CA.

Should some control be put in place?  There has been an effort to reduce the Snow Goose population because numerous summer nesting colonies are tearing up the Arctic tundra. Animal populations rise and fall, often controlled by the available food supply. Canada Geese have flourished at Lake Merritt in an altered environment, largely because of the refuge island protection and an abundance of well watered lawn grass to eat  plus the enticements of "the brown bag supplements."

To those who thrill to the sight of the Canada Goose weaving across the city to descend in regal splendor onto the lake, there are never too many geese. Sometimes wildlife management is desirable when the environment becomes threatened by overrun, but some think we should retain all the wildlife the habitat will support. In any event, we only need to look at the self-sufficient birds to see how self gained energy can be used in the most efficient way.

© 2001 Rex Burress
May 20, 2001