GOOD BIRDING

Great blue herons are disappearing from Maine’s coast and nobody knows why

Posted May 30, 2014, at 5:46 a.m.
Last modified May 30, 2014, at 6:31 a.m.
An adult great blue heron perches beside at least one nestling (others could be hunkered down) at a colony in Kennebec County.
Photo courtesy of HERON volunteer Eva Goulette
An adult great blue heron perches beside at least one nestling (others could be hunkered down) at a colony in Kennebec County.
Great horned owls can take over great blue heron nests and force a colony of herons to move.
Bob Duchesne
Great horned owls can take over great blue heron nests and force a colony of herons to move.

Sandi is a jinx. There, I said it. My wife is a jinx. She is a volunteer for the Heron Observation Network. Over the last few years, she has monitored several great blue heron nesting colonies. Her first assignment was to monitor a small colony of herons near Leonard’s Mills in Bradley. There were five visible nests. A freak microburst struck the colony and the severe weather damaged the nests. The herons never returned.

Two years ago, she was assigned another colony in Eddington. When she started, there were four nesting pairs of herons, all sitting on eggs. Two weeks later, they were gone. The reason for failure is unknown. Dutifully, Sandi offered to take on another colony that had just been identified.

A decade ago, biologists became alarmed that the number of great blue herons nesting along the Maine coast was crashing. Two-thirds of the herons were gone. I have just finished five days of birding in the Cobscook Bay area and I never saw a single heron. Not one.

A big decline often has serious implications for humans. In the past, peregrine falcons disappeared from the eastern United States when overuse of DDT caused the chemical to build up in the bodies of large raptors. Ospreys and eagles declined, too. Over time, we’ve witnessed other toxins build up in the bloodstream of birds and we have documented the ill effects. Humans are top carnivores and these dangerous chemicals can build up in our bodies, as well.

Or, maybe something is going wrong with the food supply. Herons forage in the salt marshes where sea-run fish spawn. Minnows hide in the marshes until they are big enough to go to sea. As Maine’s ground fishery has collapsed, any unknown environmental damage to marshes could prevent our fish stocks from rebounding.

Or, maybe it’s because the bald eagle has recovered. Numbers have risen and the eagle is no longer threatened in Maine. Great blue herons are large and they can stab with their dagger-like bills. They can defend themselves in a marsh when surrounded by water. But when the herons are in the air or on the nest, every advantage shifts to the eagle.

Enter the Heron Observation Network, a cadre of volunteers who are assisting biologists at the Maine Department of Inland Fisheries and Wildlife by adopting active colonies and monitoring productivity. It requires only a few visits over the early part of summer to determine how many herons are nesting in a colony and whether they are successfully raising young. Most volunteers monitor colonies near home. In fact, many of the volunteers are the folks who alerted DIF&W to the presence of a colony nearby.

The project has been successful along the coast and we now have a better idea of how dire the situation is. But one big question needs answering: If a decrease in food or an increase in eagles is the cause of colony collapse, have the herons simply moved inland? Danielle D’Auria is the state biologist who coordinates the program and she is always on the lookout for volunteers in rural areas. There aren’t as many people living where the herons could be going. To learn more, just look up the Heron Observation Network of Maine on the web or contact Danielle in the Bangor office of DIF&W.

Now, let’s return to the fact that Sandi is a jinx. Three weeks ago, we hopped into Danielle’s truck and visited a colony in Deblois behind the blueberry barrens. At least nine active heron nests had been documented at the site, and the landowner had recently reported that the herons were returning. This would be Sandi’s new site to monitor. Buoyed by the good news, we were in high spirits as we bounced over the dirt road and approached the colony from the best vantage point.

When we arrived, we discovered only one nest was occupied, and not by herons. A great horned owl had taken over, and two of the cutest, fluffiest babies were perched on the nest, watching us with suspicion. Great horned owls will also take herons, especially baby herons. In a big enough colony, the herons may tolerate the presence of nesting owls, but they clearly felt inadequate to defend this colony of only a few nests. One more colony had winked out of existence.

To volunteer, contact Danielle at the Maine Department of Inland Fisheries and Wildlife. We can’t always promise you herons. Sometimes, it’s just baby owls.

Bob Duchesne serves as a Maine Audubon trustee and vice president of its Penobscot Valley Chapter. Bob developed the Maine Birding Trail, with information at mainebirdingtrail.com. Bob can be reached at duchesne@midmaine.com.

 

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