Resident fish savvy enough to hide from herons

Putting our little ornamental ponds to bed is a priority in autumn, and it gives us our best opportunity to check on our goldfish — incredibly wary critters rarely spotted in the summer. That’s because great blue herons visit our yard, and smart fish don’t change their habits just because the big birds have gone south for the winter.

Great blue herons (Ardea herodias) are rarely spotted in suburban yards. They have long legs, stand about 4 feet tall and have a 6-foot wing span, although they only weigh between 5 and 8 pounds. They have gray-blue feathers and a black stripe over the eye. They feed on fish, amphibians like frogs, insects and even small birds.

Great blue herons breed in large groups where hundreds of birds mean lots of eyes on the alert for predators. Males stake an early claim to a nesting site and prove their worth to potential mates by stealing twigs and material from other nests. Nests can be in shrubs or even on the ground but are most often in trees. Heron droppings are extremely acidic, enough to kill the trees in an established colony, so nesting sites can move around. It’s illegal to disturb heron nests (and dangerous — they have long, sharp bills and aren’t afraid to use them).

Crows, raccoons and young hawks prey on heron eggs, and young birds are vulnerable to foxes, minks, raccoons and dogs. If they survive to adulthood, however, the birds may live 20 years.

Herons forage two to four miles from their nests and defend their hunting territories from other herons. We frequently see them in Sauk Creek and the Milwaukee River as well as in local detention ponds. In our yard they’re on the hunt for frogs since the goldfish have learned to hide. We’ve provided plenty of underwater hiding places for our fish, and as far as we can tell the local herons haven’t had any luck angling here. Catching frogs is much easier.

On the hunt, herons stealthily wade into shallow water or stalk into grasslands or farm fields. They patiently wait for their prospective meal to come into range, then snap up small prey like insects and impale larger prey like fish with their long bills. Sometimes they shake fish to break the dorsal spines before swallowing them whole.

Our area is listed as year-round great blue heron habitat, but we’ve never seen one this late in the year. With the frogs dormant and the fish protected by the ice, there’s not much for them to eat here in the winter. Most of them head south to ice-free areas. This October one tagged heron traveled from New Brunswick, Canada, to Nocatee, Fla., nonstop, making the trip in 38.6 hours.

There are over 80,000 breeding pairs of great blue herons in the U.S. The birds aren’t threatened, but their population is at risk from habitat loss due to development and climate change. Pollution leading to reduced water quality is also a threat to the survival of these and other water birds.

Great blue herons are frequently confused with sandhill cranes. Both birds fly with their legs dangling under them, but the herons can be identified by the S-curve in their necks. Cranes keep their necks straight while in the air.



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Ozaukee Press

Wisconsin’s largest paid circulation community weekly newspaper. Serving Port Washington, Saukville, Grafton, Fredonia, Belgium, as well as Ozaukee County government. Locally owned and printed in Port Washington, Wisconsin.

125 E. Main St.
Port Washington, WI 53074
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