In flight, great blue heron’s wings stretch six feet, tip to tip. Wading through water, the majestic bird stands more than three feet tall. And when it comes to building nests, the heron doesn’t hide away. Like the osprey, it constructs a large stick nest, high in a tree, 100 or more feet off the ground. In other words:
“They’re hard to miss when they’re there,” said Danielle D’Auria, wildlife biologist with the Maine Department of Inland Fisheries and Wildlife. “But that said, I don’t know if people see them as often as they should.”
The great blue heron population has dropped an estimated 66 percent on Maine’s coastal islands in the past 40 years, said D’Auria, who specializes in non-game wetland birds. The population plunge is likely connected to the growing number of bald eagles nesting on the islands. Not only do the two species compete for food, the bald eagles is powerful enough to prey on the great blue heron.
“There’s no way I’ll say that’s the only cause [for the decline in heron population], but there are lots of reports of eagles praying on heron young and adults,” she said. “The real issue is probably a food resource thing. Why else would a bald eagle choose to feed on a heron? They would probably rather eat a duck or a fish. Heron is all leg and wing bone and neck. Their mighty bill is actually quite a threat to eagles.”
Human disturbance also negatively impacts the heron colonies. Whatever the cause, the great blue heron was designated as a Species of Special Concern in Maine in 2007.
“We’ve monitored the coastal islands very closely,” she said. “What we don’t know is how the inland population [of great blue herons] has been doing over that same time period. No one has been actually paying attention to it.”
Since 2009, the MDIF&W ramped up its monitoring efforts by establishing the Heron Observation Network of Maine, or HERON, which enlists volunteers to monitor inland colony sites across the state through their adopt-a-colony program.
“We want to see if there’s a similar trend going on inland,” D’Auria said, “or if things are doing fine. Maybe they’re moving inland.”
It’s believed that the great blue herons living inland have benefited from the recovery of U.S. beaver populations, which have created a patchwork of swamps and meadows ideal for the heron to forage and nest in, according to Cornell Lab of Ornithology.
The difficulty in monitoring the inland population of great blue herons is that they’re so widespread. They nest in trees (living or dead), but about 90 percent of Maine is forested. They prefer to nest by water, but there are more than 6,000 lakes and ponds in Maine, and the state’s coastline is about 3,500 miles long.
“Almost all of the state is what you’d consider potential habitat,” D’Auria said. “Maine is huge.”
In 2009, the DIF&W Bird Group counted 1,071 pairs of great blue herons at 83 colonies (all known colonies statewide). Since then, HERON volunteers working to monitor heron colonies by ground have learned about 40 additional colony locations, though not all of those colonies are active in any given year. But they have yet to gather enough information to confidently estimate how many of the birds summer in Maine.
It won’t be until the 2015 breeding season (May-June) that a much more effective aerial survey of colonies will be conducted.
“That’s primarily based on availability of pilots,” D’Auria said. “We use the Maine Warden Service pilots and Maine Forest Service pilots to conduct these surveys because they are the most experienced at low-level flying. They know how it needs to be conducted, and we’ve worked well with them. We have some other surveys planned between now and then, mostly bald eagle surveys.”
In November, HERON partnered with Burly Bird, a Maine-based conservation sticker company, to help raise funds for the 2015 aerial survey. The public can now support the survey by purchasing a UV-coated vinyl sticker that sports a black and white silhouette of the great blue heron, a custom Burly Bird design. The sticker — which can be purchased from the Burly Bird website or through the MDIF&W’s online store — is $4, with $3 going directly to fund the survey. Sticker sales will also help leverage federal funding through Maine’s State Wildlife Grant Program.
“Once we get a population estimate, we’ll be able to repeat it five years after that and see how things have changed,” D’Auria said. “We are really trying to get at it long term.”
For information about the Heron Observation Network of Maine, visit maineheron.wordpress.com. To purchase a HERON sticker to support the 2015 great blue heron aerial population survey, visit burlybird.com or maine.gov/ifw/. To report a great blue heron colony or ask questions about HERON, contact D’Auria at email@example.com or 941-4478.