Click to Enlarge The blue heron above stands on a muskrat house to hunt, while the one on the facing page has captured a Graham’s crayfish snake that seems unwilling to become a meal. Click to Enlarge A blue heron fl ies with its neck curved and its legs hanging. Herons usually nest in trees, like this sycamore, near water. Great blue herons spend most of their days hunting. They patiently wait for prey to come within reach of their sharp bill.   Great Blue Heron by Roxanna Watts, photos by Jim Rathert These large birds are graceful fliers and skillful hunters. A tall, grayish-blue stilt walker is a daily visitor to our little stream. For the longest time he stands quietly, without so much as a ripple at his feet. Then suddenly, his slender beak darts into the water, and a squirming fish slides quickly down his long, pale gullet. The silent sentry then resumes his post. A common sight along lakes and streams in Missouri, the great blue heron is the largest of the North American herons. They can reach a height of 4 feet, with a wingspan almost 7 feet across. Easy to recognize, herons fly through the air with necks curving into graceful S-shapes and wings flapping in lazy rhythmic beats. Herons are usually solitary creatures, preferring to fish and live alone. However, when they return from their winter range in late February or early March, they gather to nest. Some birds only form pairs, but most form colonies consisting of large numbers of nesting pairs. In 1992, there were 192 active colonies in Missouri, with an average of 29 nests in each colony. In some areas, colonies may be so large that they kill all the plant life nearby. They must then spread out from the center. If you were to see one of these spreading colonies from above, it would look like a donut, with no nests in the middle. Heron to Heron During courtship, herons preen and dance, flashing elegant feather plumes and touching necks and beaks. A male may dance with several females before finding the perfect mate. When he finally makes his choice, he may offer his new mate a simple twig. This will be the first of many stick-gifts because the male does not build the nest. He only helps the female find materials. At first, the nest may resemble a large, plain platform, but if it survives the season, it may be used for many years to come. New material will be added each year until it reaches about 4 feet across. The females line the nest with fine twigs, grass and leaves. After breeding, a female lays three to six eggs—one every two to three days. This spacing means the eggs hatch over a period of time, giving a definite size advantage to the firstborn. Both parents incubate (sit on and warm) the eggs and feed the young once they hatch. As the nests fill with chicks, the colony becomes a loud and busy place. During this time, adult herons consume up to four times their normal amount of food. They then regurgitate the food for their young to eat. Because so many birds feed in the area of the colony, food supplies may run low. Studies show that young birds die from starvation more than anything else. From an ounce-and-a-half ball of fluff , the chick will reach full size in two months. On average, only one in five chicks survives to reach breeding age at three years. Those that do may live another 12 years in the wild. Still Hunting Herons hunt in a variety of ways. Sometimes they stand perfectly still and let the prey come to them. They also stalk prey by walking very slowly with their neck stretched out, ready to strike. Another common hunting technique is to crouch on a bank watching the water for a passing fish or frog. Studies show that herons catch the most prey by crouching, but they seem to prefer to use the other methods. Waiting and stalking help them catch bigger prey than the other hunting methods. Herons are not fussy eaters and will feed on fish, frogs, snakes, or even small birds or mice. They swallow food whole, unless it’s too large. In that case, a heron may strike it on the bank to kill it and then pick it apart. Some herons have choked from trying to swallow too large a meal. Others have died because they tried to swallow fish tail-first, and the fish’s fins stuck in the bird’s gullet. In the 1960s, blue herons were one of many species that fell victim to a strong insecticide, or “bug killer,” known as DDT. In 1939, a chemist named Paul Muller discovered that DDT was very good at killing mosquitoes that carried malaria and lice that carried typhus. Muller was awarded a Nobel Prize for his discovery. Unfortunately, while DDT was stopping disease, it was also dangerous to animals. By 1960, research was beginning to show that DDT levels were rising in the fat of living organisms, especially fish. Animals that regularly ate fish were greatly affected, because their DDT levels would rise with each meal. One of the effects of the DDT on fish-eating birds like herons and eagles is that it causes their eggs to have thin shells. Many times, the shells would be so fragile they would break from the weight of adult birds sitting on them to keep them warm. Today many species, including great blue herons and bald eagles, have recovered, or are recovering, from the use of DDT, which was banned in the U.S. by 1970. Unfortunately for great blue herons, the bald eagle is one of its predators. We’ll have to wait and see whether heron populations decline again—but for natural reasons this time. Words Worth Knowing When birds preen, they are using their beaks to clean, trim and sometimes waterproof their feathers. When an animal regurgitates, it brings up food it swallowed earlier, usually to feed to its young. A Nobel Prize is an annual international prize given to people who have distinguished themselves in the fields of physics, chemistry, economics, medicine, physiology and literature, or for promoting peace.