Appetite for baby chicks hurts herons' reputation


POSTED: Monday, September 07, 2009

Last week as I looked through my literature on Hawaii's shorebirds, a headline in the Hawaii Audubon Society's journal, Elepaio, stopped me. It said, “;The Black-Crowned Night Heron: The Bad and the Good.”;

The bad? What could be bad about these stunning birds with the ruby-red eyes? As Hawaii natives, aren't they part of a balanced ecosystem?

Yes, but the more correct term is ecosystems, plural, because these herons hang out in just about every place in Hawaii that's wet. Freshwater streams, marine tide pools, brackish marshes, golf course water traps, sewage treatment plants and aquaculture facilities all attract these adaptable water birds. Last weekend I even saw one perched on a pier in the Ala Wai Boat Harbor.

The tilapia-packed drainage canals in Ala Moana Beach Park host resident herons, and it's a great place to watch these birds fish. I once saw a regal-looking heron snatch a tilapia from the canal in a strike so fast, I barely saw the bird move. But the fish was too big to swallow. With jerks of its beak, the heron, a handsome male with four white breeding feathers streaming from the back of its black crown, turned the struggling fish around and around.

I was sure the determined bird would get its prize down its throat, and also sure the fish would be dead by the time it happened. To my surprise, though, the heron practiced catch-and-release fishing. When it couldn't swallow its catch, the bird dropped the fish back in the water. The stunned tilapia hovered for a moment and then darted away to rejoin its school.

Besides being native to Hawaii, black-crowned night herons have made it on their own to every continent except Australia and Antarctica. They raise chicks just about everywhere, too, from sea level to nearly 16,000 feet, and from the tropics to the high latitudes.

The herons that nest in warm climates do so year-round and don't migrate. The ones that inhabit cold climates nest in the spring and migrate to balmy locations in the fall.

The species' remarkable success comes from the bird's ability to catch and consume just about anything it comes across. Black-crowned night herons eat, and usually manage to swallow, crabs, shrimp, fish, frogs, mice, insects and carrion.

They also have no qualms about snatching chicks from the nests of Hawaii's endemic and endangered stilts and moorhens.

One time in the protected stilt nesting grounds of Marine Corps Base Hawaii in Kaneohe, a bird researcher flushed 40 herons into the air at once. Another time in Maui's wetland preserve, Kealia Pond, workers counted 56 juvenile herons.

And that's the bad of Hawaii's black-crowned night herons. They eat baby birds.

There's plenty of good in these birds' big appetites, too. By eating mice, bugs and bullfrogs, these water birds keep some of Hawaii's alien pests in check. And in eating dead animals, the herons help keep our wetlands clean.

If our endangered wetland birds could recover their numbers to the point they were no longer threatened with extinction, then our heron's normal chick-eating behavior would also be a good thing, natural selection at work.

We can help all our native water birds by supporting the creation of predator-proof wetlands. It's the way to take the bad out of heron headlines.

Susan Scott can be reached at www.susanscott.net.