Great Blue Heron - Photo: Dow Lambert
The Great Blue Herons of Dungeness Bay
by Bob Boekelheide
March 2023
While birding recently at Three Crabs, it surprised me to see only one Great Blue Heron foraging on the giant mudflats. Where are the herons? There were thousands of Dunlins and hundreds of gulls, but only one heron. Are the herons disappearing? Or is it normal to see fewer herons this time of year?
Fortunately, the answers to these questions come from OPAS citizen science projects. Between 2014 and 2018, OPAS volunteers counted birds at Three Crabs as part of the Three Crabs Estuarine Restoration Project, coordinated by the North Olympic Salmon Coalition and WA Dept of Fish and Wildlife. During this study, OPAS volunteers counted birds at Three Crabs three times each month for five years, tallying all the birds we could find within about a hundred-acre area on the mudflat, beach, and bay, including Great Blue Herons.
Great Blue Herons foraging in Dungeness Bay. Photo: Bob Boekelheide.
Great Blue Herons are definitely a common species in Dungeness Bay, easily visible as they hunt in shallow water or roost in uplands above the beach. Despite this visibility, we found that herons are not here all the time. Over five years, we found that they only occurred on 81 percent of our 152 surveys at Three Crabs.
We found that herons have a very distinct annual cycle in Dungeness Bay, with their lowest numbers here in winter and spring (Figure 1). Their abundance picks up through June and July to a clear peak in August and September, when they disperse from their nesting colonies (Figure 1). Yes, we have herons here year-round, but if you want to see lots of herons you need to look in late summer, not late winter.
During our five-year study, the highest count within our small study area occurred on August 27, 2018, with 26 herons. Coincidentally, the highest count anywhere in Clallam County, as found in eBird, was 66 herons observed in Dungeness Bay on September 4, 2021, right around the same time of year.
Great Blue Herons showed no increase at Three Crabs during the nesting season, simply because they usually do not nest in Dungeness. At their nesting colonies in other parts of the Salish Sea, they occupy territories and start building nests during winter, then lay eggs in March and April. The highest numbers we see in Dungeness Bay in August and September coincide with the time of year when herons disperse from their nesting colonies, including recently-fledged juveniles.
The largest heron colonies within 50 miles of Clallam County are likely on the shores of Padilla Bay in Skagit County, where there are hundreds of nests clustered in trees at March Point and Samish Island. During the nesting season, herons forage all over the mudflats and shallow waters of Padilla Bay. The closest colony of any size to Clallam might be at Beacon Hill Park in Victoria, B.C., about 20 miles as the heron flies. The Beacon Hill Park heronry has had a difficult past, though, sometimes abandoned because of eagle predation.
Great Blue Herons try to nest in Clallam County, but as far as we know nearly all recent nesting attempts have failed. Herons have built nests in trees at Three Crabs, along the Dungeness River, up Palo Alto Road, at Diamond Point, and near Neah Bay and Clallam Bay. Within a few days or weeks the birds usually abandoned their sites. Perhaps these were young, inexperienced birds that couldn’t resist the urge to gather sticks and build nests, but they never seemed to reach the point of fledging chicks. Does anyone know of successful Great Blue Heron nesting attempts in Clallam County? If you do see herons trying to nest, it's important to give them space and not disturb them.
Great Blue Heron standing in a nest beside the Dungeness River, June 2020. Photo: Bob Boekelheide.
One of the most interesting Clallam nesting records comes from Hank and Raedell Warren of Port Angeles. In 2013, while walking up the Lake Angeles Trail south of Lake Dawn, Hank and Raedell heard strange squawking sounds in the coniferous forest at about 2500 feet elevation, more than five miles flying distance from the Strait of Juan de Fuca. Looking closer, they discovered that the sounds came from half-grown Great Blue Heron chicks sitting in three nests high in the Douglas-firs. Why in the world would Great Blue Herons nest so far up in the Olympic Mountains?
The answer likely came the following year, when Hank walked to the same spot during spring 2014. Hank found the nests, but he also discovered eggshells and feathers scattered on the ground below the nests. There were no herons to be seen. What he found instead were three Bald Eagles flying through the forest and landing near the nests. Like Hank said, “The eagles and feathers explain the absence of herons.” A year before we thought these herons might have figured out how to avoid eagle predation by nesting in an obscure, out-of-the-way place, but the eagles eventually found them.
As you might have guessed, Bald Eagles have a huge influence on the nesting success of Great Blue Herons. For example, the colony at Beacon Hill Park in Victoria, B.C., has a checkered history of abandonment because of eagles. The interpretive signs below the park’s nesting area even delineate what they call the “Eagle Period,” when Bald Eagles appear at a specific time in the herons’ nesting cycle to eat chicks in the nests. The herons have no defense against marauding eagles.
In Dungeness Bay I also witnessed an eagle kill an adult Great Blue Heron, by quickly swooping down from the sky and landing on the heron’s back. I suspect the heron may have already been injured, though, because it made no attempt to fight back or escape.
Data from the Sequim-Dungeness Christmas Bird Count show a distinct decrease in the number of Great Blue Herons counted over the last 30 years (Figure 2). There is quite a bit of variability between years, however, which is typical of Christmas Bird Counts. After all, it is tough to control things like weather, tides, and counters each year. Regardless, herons dropped from an average of about 100 per year during the 1990s to an average of about 70 per year during the last 10 years. This is consistent with declines in herons elsewhere in the Pacific Northwest, as described in Birds of the World. Could some of these declines be due to increased numbers of Bald Eagles?
The Great Blue Herons we see in Clallam County are likely the Northwest coastal subspecies, Ardea herodias fannini, which nests from southeast Alaska to Washington state. A. h. fannini is the darkest gray and one of the larger Great Blue Heron subspecies, which fits in with our darker, more northerly climes. This subspecies is mostly considered non-migratory, although they disperse widely through coastal areas of the Salish Sea after nesting, including the north Olympic Peninsula. The entire population of A.h. fannini might number 8,000 to 10,000 birds, with about half of those nesting in Washington State.
Herons basically eat whatever animals they can catch, including fish, mammals, birds, amphibians, and crustaceans. In Dungeness Bay I’ve seen them eating flatfish, sculpins, gunnels, crabs, and what looked like smelt or perch. Herons are unwelcome visitors at backyard fish ponds and local hatcheries, where they may gobble down lots of fish very quickly. But seriously, don’t you think it is a noble end for your prized koi to end up in the belly of a Great Blue Heron?
It’s always entertaining to watch a heron try to swallow a big starry flounder (see Dow Lambert’s photo), grossly stretching their throat to accommodate the fish. Sometimes herons bite off more than they can chew, as there are records of herons choking to death trying to swallow large prey items.
Great Blue Heron with a captured starry flounder. Photo: Dow Lambert.
The oldest banded Great Blue Heron on record was 23 years old, but very few likely get that old. A demographic study in a British Columbia colony found that the average age of nesting adults was 5.6 years old. Most herons begin nesting in their second year, so an average adult might be lucky to nest for four or five years during its lifetime. Their average clutch size in British Columbia was about four eggs, but so many nests failed that the average number of chicks fledged per nesting attempt was two or less. Additionally, banding studies show that the majority of young herons die within their first year after they leave the nest. It’s not easy being a heron.
Lastly, I’d like everyone to keep an eye out for “Carte Blanche,” a partially-leucistic Great Blue Heron that’s been seen in Dungeness Bay for the last couple years. It stands out from the crowd, because, unlike a typical gray GBH, this one has a bright white belly and white markings on its head. The white belly is somewhat reminiscent of a Tricolored Heron, but its size and behavior are clearly Great Blue Heron. My wife, Barb, named the bird “Carte Blanche,” or “Blanche” for short.
Spring is here, and so are bird songs. Every spring is precious, when the Earth comes alive with life and sounds. You must go birding! Learn the bird songs! If you see or hear anything of interest, please let us know on the OPAS website: https://olympicpeninsulaaudubon.org/contact-us
Many of the interesting facts about Great Blue Herons in this story came from Birds of the World, an on-line resource available through Cornell Lab of Ornithology. I highly recommend that all bird aficionados get an online subscription to Birds of the World, both for its wonderful information and to support the Lab of Ornithology.