Window on Nature
By Lowell & Kaye Christie, F47246
People feel uncomfortable when they’re being followed, but cows don’t seem to mind. If one of them turns around and sees a chicken-size bird following in its tracks, it gives a bovine shrug and continues eating. The beasts are accustomed to having cattle egrets dogging their hooves and even hitching a ride on their backs.
All species of egrets (at least all those in North America) are beautiful and graceful birds “” even when they’re foraging for insects, small frogs, and other food. But somewhere along the evolutionary line, cattle egrets veered from feeding in aquatic habitats, as do other herons. Once they discovered the advantages of following cattle, they made it their preferred method of finding food.
You’ve likely seen livestock meander around a field in search of more or better grass to feed upon. As they move, the birds literally follow in their footsteps, snatching up the edibles uncovered by the cattle’s hooves.
You may have heard of cattle egrets referred to as “tick birds.” While they do spend some of their time parked on the backs of cows, they’re not there to detach ticks. Their long bills aren’t designed to pry the insects off. But if a tick is moving, it’s down the hatch.
Cattle egrets are believed to have evolved in Africa. Many centuries ago, the birds didn’t specialize in a particular species; anything with hooves would do “” rhinos, zebras, wild cattle, even giraffes. But once the birds discovered domesticated cattle, they were really on to something. Cows grouped in a smaller area meant plenty of food and easy eating. As the centuries passed, cattle raising became more popular throughout Africa, and into Europe and Asia. The cattle’s white-feathered buddies went along.
With the development of agriculture came new opportunities for cattle egrets as farmworkers planted fields and harvested crops. Many more creatures were flushed from the soil by plows and tractors than by wandering cows and bulls. As the number of birds increased, they spread across the land. Today, cattle egrets are established on all seven continents. And, as hard as it may be to believe, it all happened well within recorded history. The egrets first spread north to deforested areas of Europe and Asia, and only later made their way across the Atlantic Ocean to South America.
It was 1877 before cattle egrets were actually documented in the Americas. Consider the effort it took these birds to get here. The distance from the bulge of West Africa to the coast of Surinam, where the first egret pioneers landed, is 1,780 miles. Even with a boost from prevailing trade winds, it would have required 40 hours of flapping before the egret reached landfall.
A stream of cattle egret immigrants arrived to build a huge South American population. At the time, humans in South America were clearing tropical forests for ranches, so the birds found a ready-made habitat as well as plenty of bovine hosts. A century later, cattle egrets ranged all the way to Tierra del Fuego at the southernmost tip of South America. The cross-ocean flapping continues even today, as cattle egrets are routinely sighted at sea.
The first breeding pair of cattle egrets documented in North America was spotted in Florida in 1953. By the 1960s the species had made its way to California. It continued to spread, until now cattle egret colonies are found in nearly every state in the continental United States.
In Texas alone, it’s estimated that 300,000 pairs of cattle egrets nest and raise their young. That’s quite an accomplishment considering the birds didn’t take up residence there until the late 1950s.
Cattle egrets will never become as widespread as another immigrant bird species, the dreaded starling. The egrets are far more beautiful and far less noisy, but do not tolerate the cold as well.
Today, cattle egrets winter in Southern California and across the southernmost states to the Atlantic Coast. Lesser numbers are found along the East Coast all the way to New England. When spring arrives, they spread out across most of the United States.
In the upper Midwest and in Canada, cattle egrets are mostly considered to be vagrants, short-term visitors blown off course. Amazingly, the birds have been spotted as far north as Great Slave Lake in the Northwest Territories. Naturally, they can’t remain in northern regions all year, so when the days get shorter the cattle egrets migrate south along with the motorhoming “snowbird” crowd.
Expanding their territory across so many miles in so few years was, to some extent, made possible by the fact that adolescent cattle egrets don’t hang around with their parents. Once they’re able to find their own food, they take to the skies. Bird-banding records document their dispersal. In one instance, a banded cattle egret was found 2,600 miles from its natal rookery.
Lest we forget, the cattle egret population explosion coincided with a worldwide boom in cattle farming, and especially with the creation of pasturelike habitats for grazing. Scientists have records indicating that a herd of cattle, shuffling their feet as they walk, kick up enough bugs for an egret to eat at a rate of two or three insects a minute.
Thanks to their atypical method of finding food, cattle egrets remain the only members of the heron tribe not tied to aquatic habitats. They still nest near watery places, and are quite willing to dine on creatures they can spot and grab along the edges of lakes or in marshes, but their overall survival is more closely tied to bugs kicked up by grazing cattle and other herbivores.
Here are a few more interesting tidbits about cattle egrets before we grab our binoculars and get out there with the birds. It’s been found that in some New Jersey garbage dumps, bulldozers plowing through the debris serve as surrogate cows for cattle egrets. Another source indicated that in Florida, cattle egrets have gotten into the habit of dashing onto highways to snatch bugs knocked down by cars, a sometimes fatal form of foraging.
It’s amazing to think back to when we first began seeing cattle egrets in the late 1970s “” we didn’t even know they were immigrants. That awareness came later, in the company of more seasoned and knowledgeable birders.