The Story Of The Three Egrets
By Tony Burton
Three related but different species of white herons can often be seen somewhere near water almost anywhere in Western Mexico, including Lake Chapala and other nearby ponds and drainage ditches. They are the great egret, the cattle egret and snowy egret. If all three species are seen side by side, they are very easy to tell apart: the small ones, about 50 centimeters (20”) tall with yellow or orange beaks (red when breeding) and dark feet are cattle egrets. The middle sized ones, of a different shade of white, with dark bills and yellow feet, are snowier. And the largest ones, one metre (40”) tall, yellow-billed with black legs, are great egrets.
Cattle egrets nest in colonies, usually near water, with other herons, ibises, cormorants and anhingas. After the male attracts a female, both egrets build the nest from twigs or reeds, depending on the available vegetation. Nests from previous years are sometimes reused. Since other birds may steal their nesting materials, it is common for one bird (usually the male) to gather the nest material while the other acts as builder and security guard. The female lays from two to six eggs, at intervals of two or three days, thus ensuring that there is always a variety of sizes of young in the nest. The youngest chicks are the most likely to be preyed upon by grackles, purple gallinuies, gulls and snakes, or to starve if food is scarce. Both parents share fairly equally in incubation and in bringing food to the young, who begin to fly when about 40-50 days old.
Unlike its two cousins, the cattle egret (Bubulcus ibis) is often seen feeding alongside cattle as they graze. Indeed, the “Bubulcus” of its Latin name means “concerning cattle”. While they also eat “solo”, as do most herons, it is their use of cattle as insect beaters that makes them special. Studies of the feeding success of egrets foraging alone, compared with others looking for a meal next to grazing cattle, have shown that those near cattle captured significantly more insects, with far less expenditure of effort (using the number of steps taken as the measure). Analyses of their stomach contents have shown grasshoppers to be their preferred diet. While some authors have suggested that the egrets serve the cattle by deticking them, this has never been proven by the contents of their stomachs!
The great egret (Casmerodius albus) and snowy egret (Egretta thula) both prefer an aquatic diet. Great egrets have been reported to eat fishes, frogs, salamanders, snakes, and even tasty crayfish in addition to grasshoppers and mice. Snowy egrets also like shrimp and crab meat. Many snowy egrets feed by using one foot to stir up the mud in the shallow water on the edge of a pool, frightening prospective prey into view, then stabbing them repeatedly with ever- ready beaks. They will also “eat on the run”, dashing through shallow water, wings outstretched, after the next item on their menu.
These three close relatives, often seen in large flocks, add a dash of sparkling white to the Mexican landscape. The cattle egret, perhaps more than the other two, has claim to fame as being the earliest “snowbird” in the Chapala area to fall in love with the area’s climate, beauty and people sufficiently to settle here permanently!
(Ed. Note: Tony Burton is a naturalist, eco-tourism guide and freelance writer. His book, Western Mexico -A Travelers Treasury, includes details of many of the natural and historical wonders of Western Mexico.)
For more information about Lake Chapala visit: www.chapala.com