WILDLIFE IN RYERSONS WOODS
Great Blue Heron
Ardea herodias

Hiking along the Des Plaines River you may come upon a great blue heron gliding overhead or sitting motionless at the water's edge watching quietly and patiently for an unsuspecting fish or frog to swim by. At four feet, with a six-foot wingspan, this is the largest of the North American herons. It is easy to identify the majestic long legged dark blue-gray birds with brown neck, chestnut thighs and white cheeks, throat and crown; the adults with long black stripes along each side of their head.

Great Blue Heron NestsGreat Blue Herons build their nests along waterways in large trees with wide, open, spreading branches such as sycamores or cottonwoods. Constructed of sticks, the nests are lined with reeds, grasses and moss to make a soft bed for the two to four large blue eggs that are laid in the spring. Eggs hatch in just 28 days. Both parents care for the chicks as they grow, flying up to 15 miles in search of food. In about two months, the young herons are ready to fly and leave the nest.

Surviving their first winter is the hardest, but then, with a good environment, the great blue herons may live up to fifteen years.

The heron diet consists mainly of small fish which they spear with sharp pointed beaks and swallow whole. They will also eat turtles, crayfish, lizards, frogs, snakes, insects and even small birds and rodents.

In warm winters, some of the herons may winter over along the Des Plaines River which remains largely unfrozen. But generally, the birds begin to fly south in autumn as wetlands and ponds begin to freeze. They will return to the same nesting sites in the spring, although over time, the trees will begin to deteriorate and die as year upon year of waste is deposited on their branches. Then the herons will have to find a new stand of trees for their nests.

Once pesticides were the greatest threat to our populations of herons and other large birds such as the egrets and double-crested cormorants which were once on the Illinois endangered species list. In recent years, the birds have faced new challenges with the disappearance of nesting sites and changes in habitat and water quality. Lake county is fortunate to have several successful colonies of great blues nesting within its boundaries. With wetland restoration projects, installations of some man-made nesting structures, and construction of reservoirs that provide additional feeding at many of our corporate centers, their chances of survival continue to improve.

(photo of heron nests courtesy McHenry County Cobservation District)

Great Blue Heron
Crayfish
(photo courtesy Fermi Natrional Accelerator Lab)


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