Heron rookery active again

PHOTOS BY GARRY BRANDENBURG — Great Blue Herons are a common wetland bird. It is tall, slender, and uses its pointed beak and lightning fast striking neck to spear fish, frogs, small mammals, insects or even small birds. These herons build colony nests where all the eyes of these birds prevent any unwarranted intruders. Great blue herons have a high percentage of rod-type photoreceptors in their eyes for improved night vision. In fact, they can forage for food sources day or night.

GREAT BLUE HERONS (Ardea herodias) are very interested at this time of year in catching foods and building nests. Instead of having a single isolated nest high in a tree, this heron species likes the company of many. Some places in North America have documented more than 100 nests in a grouping of tall trees. In the case of today’s image, there are about two dozen nests. A former nest colony, called a rookery or heronries, near this site, had 48 spindly-looking twig nests. By the time the male gathers enough twigs and small sticks, the nest can appear to be quite bulky. Then stand back at a distance, before the tree leaves out, and those blobs of many nest structures really stand out.

Great blue herons tip a scale at maybe 5 to 6 pounds. This is partly due to a hollow bone structure. Limb bones may appear smooth on the outside, however if broken open, will display a network of criss-crossing internal bracing. This makes the bones much lighter while still maintaining strength. Vertebrae in a heron’s neck are shaped to allow for maximum movement side-to-side or up and down. When hunting, the bird may hold its neck tall and straight, but if a fish is detected close to the surface of the water, a stealthy approach is used while the neck is placed in a large “S” shaped position. At just the right moment, the neck extends forward at lightning fast speed. The bottom bill is the spear to pierce into the flesh of the fish. The top bill clamps down to hold the squirming fish and prevent escape. Once firmly grasped, the heron will flip the fish around to position if head first into the bird’s throat. A few gulps later and the fish is deep into the stomach of the heron.

Great blue heron nests will typically have two to six eggs. Each egg is about 2.5 to 3 inches long and about 2 inches wide. It takes 27 to 29 days for incubation to complete its duties. After hatching, the young are brought food by the parent birds. Young eagerly insert their bill into the throat of the adult. Young will be in the nest for a long time, anywhere from 49 to as long as 80 days. Any young bird having the misfortune to fall out of the nest will die on the forest floor.

Every rookery will be relatively close to water sources such as a river, lake, pond or stream. For obvious reasons, that is where fish are to be found. Amphibians and small mammals like mice, voles or shrews are usually not too far away from water. Insects like water edge habitats also. And a heron standing motionless along the bank vegetation of water sources may have the perfect camouflage. Herons are masters of stealth.

TRUMPETER SWANS with neck collars may be in an area near us. Otter Creek Wildlife Area in Tama County is one place where nesting of free flying pairs is likely. Young cygnets in 2019 and 2020 were captured by DNR biologists and green neck bands were installed. Large white letters/numbers will be engraved on the neck band. Should your binoculars or spotting scope reveal the number, write down the location and date. Forward the information to me and I will see to it that the right people get that data. A few years ago, a swan from northern Iowa made a flight to Great Slave Lake in northern British Columbia. Most banded birds are likely to migrate but for lesser distances.

Other trumpeter swans have miniature GPS transmitters that send out a signal once every 15 minutes. The satellite data points can be plotted on a map of North America to see where the bird goes. This is very interesting information now the restoration program that began in 1993 resulted in 15 pairs of nesting birds by 2003. In 2010 there were 42 nesting pairs in Iowa. In 2016, more work was begun to track swans with GPS transmitters as they moved about in Iowa.

APRIL is here. What will this month bring us? Sunny warmer weather for sure, rain for sure, more migratory birds appearing and tree leaf emergence. Grasses will green up and people will think of gardens. Farmers will be ready to till the soil and plant crops. Spring is very welcome after a long cold winter.

However, in case your memory needs a reality check, do not forget the blizzard that brought 20 inches of snow, howling winds of 65 mph, power outages and traffic to a standstill for three days on April 9 – 11, 1973. It was a humdinger of a winter fury reminder of how weather systems can develop to bring snow to us in huge quantities. I was here in Albion to take care of two little boys. Wife Bobbi was safe and at work at the hospital, working overtime and extra shifts to cover for nurses unable to travel due to snow blocked roads. Locally, police had to resort to snow machines from volunteers. Nurses and doctors got to and from the hospital on snow machines. That winter blizzard was not a normal happening, but it did happen. I’m trusting Mother Nature will be nice this April. If I’m wrong, well, so be it.

During April, we can expect days to get longer quite quickly. On April 1, our day length was 12 hours, 42 minutes long with a sunrise at 6:53 a.m. and sunset at 7:35 p.m. When April 30 arrives, day length will be 14 hours and zero minutes long. Sunrise will happen at 6:08 a.m. and sunset will be at 8:07 p.m.

DNR biologists will conduct spotlight surveys over standard routes looking for deer and other furbearer mammals. In the waters of major glacial lakes or large reservoirs, fisheries crews will gill net walleye to gather fish eggs for hatcheries. And for hunters, wild turkey seasons begin on April 12. Mushrooms may pop out of the ground as those folks seeking morel mushrooms to eat go exploring area forest lands for these delicacies. And of course, water temperatures continue slow rises and fish respond accordingly. Flowers will begin to sprout blossoms and insects will begin to buzz. Snakes will come out of deep burrows. So will woodchucks and thirteen-lined ground squirrels. April is here again. It is welcome.

Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a graduate of Iowa State University with a BS degree in Fish & Wildlife Biology.

Contact him at:

P.O. Box 96

Albion, IA 50005


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