D e s e r t E x p o s u r e
January 2010
Vagabond of the Water Birds
The far-flying Cattle Egret has found its way across the Atlantic and all the way to New Mexico.
Story and photos by Jay W. Sharp
For some murky reason, late in the 19th century, the Cattle Egret began an expansion of its range at a speed and scope that rivals the greatest ever recorded for any avian species, according to top authority Ray C. Telfair II, writing for the Birds of North America Online.
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A Cattle Egret with the bird's typical "hunched" posture, at the El Paso Zoo |
Evidently native to Andalucan Spain, southern Portugal and tropical and subtropical Africa and Asia, the bird made its first known appearance in the Western Hemisphere, on the northeastern coast of South America, in 1877. It had flown completely across the Atlantic Ocean, likely beginning its journey somewhere along the west coast of Africa.
From its South American outpost and probably other trans-Atlantic crossings, it would colonize much of that continent, west and south, during the following decades. It then turned up in the Caribbean Basin in the 1930s and 1940s. It extended its range across Central America and Mexico during the 1950s and 1960s. It had reached the United States, in Florida, in the early 1940s, and began following coastlines and drainage systems to lay claim to new territory across the lower 48 states as well as southern Canada. Although the Cattle Egret's principal breeding range in the United States lies in the Southeast, it now nests in most of the contiguous 48 states, according to Cathryn Wise-Gervais in the Arizona Breeding Bird Atlas. In fact, it has become the most abundant of its family, the ardeidae (egrets, herons and bitterns), in our country, its numbers exceeding all those combined for its close kin, according to the Animal Diversity Web.
Meanwhile, the Cattle Egret founded new colonies in Australia and New Zealand in the middle of the 20th century and in Western Europe in the second half of the 20th century. In fact, as Telfair indicates, the bird now occupies much of the world except for those regions with extreme climates.
The Cattle Egret likely made its first appearance in New Mexico around the 1960s, about the same time it turned up in Arizona and Colorado. It is still spreading across the Southwest, leaving a lot of feathered drifters in its wake.
Distinctive Features
Egrets Only
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Among the smaller of the closely related species, the Cattle Egret has a length of about a foot and a half, a wingspan of about three feet and a weight of a pound or less. (The male is somewhat larger than the female.)
In the non-breeding season, the bird has white plumage, a yellow bill and dark gray to carrot-colored legs. During the breeding season, it produces orange plumes on the back of its head, on the higher part of its breast and, sometimes, on its lower back between its wings.
Compared with the other egrets and herons of similar size, the Cattle Egret generally has shorter legs, neck and bill; standing or perched, it often assumes a hunched stance. Like other egrets, it flies with its neck folded into an "S" shape. It walks with a swaying swagger. Its most common call sounds like "RICK-rack," with the accent falling on the first syllable.
Migratory and Dispersive Habits
The Cattle Egret, say ornithologists, yields to calls both to migrate and, simply, to disperse, especially if it is young and restless. In fact, its preference often seems unclear. A true vagabond, the Cattle Egret, says Telfair, tends "to wander extensively, exhibiting repeated incursions, temporary colonizations, retreats and establishments." It has been seen — from ships in the middle of the Atlantic Ocean — flying west, toward South America. (By contrast, some populations — for instance, some along the Texas Gulf Coast — remain essentially sedentary.)
If migrating across the United States, the Cattle Egret follows a leisurely and episodic route southward in the fall, joining a wave of its own as well as, perhaps, other related species, moving along the nation's flyways. It retraces its route, with only slightly more urgency, in the spring, again joining a wave of comrades in its flight to nesting grounds. Its breeding season will extend from late spring into the fall.
Typically, in a plentiful population of the birds, it is the young Cattle Egret — the juvenile struck by wanderlust — that feels drawn to seek out new horizons and new associations. Once it leaves, it never returns to its natal rookery.
Habitat and Diet
Unlike its fellow ardeidae, which depend heavily on aquatic habitats for food sources, the Cattle Egret forages in scattered flocks in open pastures and fields and, occasionally, very shallow waters. It feeds on a highly variable diet, which can include insects (especially grasshoppers and crickets), spiders, centipedes, millipedes, moths, mice, birds' eggs and nestlings, frogs and, to some extent, fish.
Adaptable and resourceful, it often associates with grazing animals, both domesticated and wild, capitalizing on the opportunity to feast on disturbed prey. It may even ride, totally ignored, on the back of a grazer (often a cow, hence the common name "Cattle Egret"), watching with a sharp eye for prey. "When feeding," says the Animal Diversity Web site, the bird "usually walks in a steady strut, followed by a short dart forward, and a quick stab," putting an end to its prey. It may even "leapfrog" over a fellow Cattle Egret to reach its mark.
In the Southwest, the Cattle Egret, along with other egrets, typically builds its nest along shorelines of rivers, wetlands, lakes and reservoirs, usually in a rookery. The Cattle Egret places its home some feet above ground level in gallery forests, or "bosques," of willows, cottonwoods, mesquites, tamarisk, Russian olive and other trees. The flexible and gregarious bird may also build its nest in commercial groves or residential areas.
Behavior and Life Cycle
While the Cattle Egret seems to feel the urge to mate later in the season than its native relatives, it responds vigorously when the time does arrive. The male, along with several other Cattle Egret males, chooses a nesting area. He picks out his specific nesting site. He proclaims ownership of the immediately surrounding area, threatening any would-be trespassers.
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A juvenile Cattle Egret, probably
about eight weeks old, that has appropriated a visitor bench at the Mesilla
Valley Bosque State Park, just west across the Rio Grande from Mesilla. |
Much like other egrets and herons, the male then, writes Paul Johnsgard in Birds of the Great Plains, "performs several visual courtship displays ('stretch,' 'twig-shaking,' wing-touching,' 'forward-snap,' 'flap-flight,' and 'forward')." A female, no doubt drawn by his charming behavior, flies to him, "landing on his back, and subduing his aggressive tendencies by repeated blows on the head. These blows gradually change to nibbling after the male has ceased to fight back. Mutual back-biting is used thereafter by the pair as a greeting display, and it often precedes copulation."
As the mating process plays out in several episodes over the next few days, the male escorts the female to his chosen nesting site. The pair establishes a bowl-shaped nest of sticks and twigs, perhaps appropriating and adapting an abandoned nest from a previous season, scavenging an old nest for building materials, or building a sparkling new nest from nearby materials. The male guards the couple's new home continually while his mate prepares to lay, typically, three or four pale blue eggs at a rate of one every other day.
The two incubate the clutch for some three weeks, when the hatch begins, typically at a rate of one every other day. As the process unfolds, says Telfair in his Birds of North America Online, a parent "flies to a nearby water source, dips abdominal feathers, then quickly returns to incubate, thus cooling eggs and preventing desiccation."
A newborn hatchling, helpless and down-covered, lacks the strength to stand or even raise its head. Over the next six to eight weeks, however, the chick — carefully nurtured and protected by its parents — grows and develops rapidly. It feeds — sometimes with voracious greed — as its parents offer it a diet of regurgitated insects and other prey. It grows the white plumage of its species. It takes short, exploratory ventures from its nest. It attains the size of an adult. It learns the skills of foraging. It masters the art of flight. Finally, it takes its place in its Cattle Egret community, perhaps beginning to feel a compelling urge to migrate or just explore new worlds.
At about two years of age, the Cattle Egret reaches sexual maturity, producing the orange plumes to signal its readiness to raise its own family. With luck, the bird may live seven or eight years and perhaps twice that long.
Life's Hazards
The Cattle Egret has capitalized on its adaptability and resourcefulness in an extraordinary expansion of its range and increase in its population, but like all wildlife, it faces an array of hazards. According to Telfair, its eggs may be stolen by grackles or crows. In some areas, its nestlings may be attacked by the Red Imported Fire Ant. Its young may also be taken by raptors, raccoons, foxes or even domestic dogs. The Cattle Egret may make a predator pay a price, however, with a flurry of beating wings and fierce pecking.
Jay W. Sharp is a Las Cruces author who is a regular contributor to DesertUSA, an Internet magazine, and who is the author of Texas Unexplained. To read all his guides to birds of the Southwest, see www.desertexposure.com/birds