Maine’s coastline and inland wetlands support several colonial wading birds, but most birdwatchers only ever encounter three of them regularly. According to the Maine Department of Inland Fisheries and Wildlife, the state’s colonial wading birds run from great blue heron and snowy egret down to great blue heron, snowy egret, glossy ibis, black-crowned night-heron, great egret, little blue heron, tricolored heron, and cattle egret, listed from most to least abundant.
Of that group, the types of herons in Maine that show up most consistently in marshes, rivers, and tidal flats are the great blue heron, the green heron, and the black-crowned night-heron. Each one hunts differently, keeps a different schedule, and faces a different conservation outlook.
This piece breaks down how to identify each species, where they turn up around the state, and why two of the three are being watched closely by state wildlife biologists.
1. Great Blue Heron
The great blue heron (Ardea herodias) is the heron most people picture when they think of a wading bird. Maine’s own wildlife agency describes it plainly: the Great Blue Heron is Maine’s largest heron, with long legs and neck, and a thick, daggerlike bill, blue-gray with a wide black stripe over the eye, and during breeding, its head, chest, and wing plumes give it a shaggy appearance.
Standing birds reach two to three feet tall, and these large creatures have a wingspan of nearly six feet, which is part of why they’re so hard to mistake for anything else. If you want a refresher on how herons compare to the rest of the blue-toned bird species found across North America, the great blue heron’s slate coloring is a useful reference point.
Habitat needs are broad but specific. Great Blue Herons use a variety of habitats, but are most closely associated with wetlands, both freshwater and saltwater, where they feed on fish and amphibians, and they will also forage in upland fields for reptiles and small mammals. Nesting is a group affair: they build large platform stick nests in live or dead trees, typically 2.5 to 30 meters above the ground, often in colonies that may contain scores of nesting pairs, concentrated in the southern and central interior portions of the state. Anyone comparing wetland bird communities more broadly might also look at the wider world of water birds that share these same marshes and flowages.
The population trend is the part that worries state biologists. Monitoring efforts have revealed a 31% statewide decline in nesting pairs since 2009, and coastal colonies have been hit even harder — pairs on coastal islands have dropped by 93%, likely due to an expanding Bald Eagle population.
As a result, Great Blue Heron is listed as a species of Special Concern in Maine. There’s a bit of encouraging news in recent surveys, though: in the 2024 season, 66 volunteers surveyed 92 great blue heron colonies, and documented 694 nesting pairs at 55 active colonies statewide.
Pro Tip: Great blue herons follow the tide as much as the calendar. Along the coast, check mudflats and shallow bays about an hour before low tide, when fish get pushed into water shallow enough for a heron to wade and strike.
Migration adds another layer of seasonality. Most migrate south each fall, some as far as Mexico and the West Indies, while others attempt to remain all winter in southern Maine. Maine’s Heron Observation Network has even tracked individual birds by GPS to confirm exactly where they go — one tagged female, nicknamed Cornelia, is an adult female great blue heron tagged with a GPS transmitter who nests in Maine and migrates to the Bahamas for the winter.
Birders curious how Maine’s population compares to other states can check similar breakdowns for herons in Illinois, herons in Minnesota, or herons in Oregon — the great blue heron shows up on nearly every one of those lists, since it ranges across almost the entire continent.
2. Green Heron
Where the great blue heron is impossible to miss, the green heron (Butorides virescens) is built to disappear. It’s described as a small, dark heron with a blue-green back, rusty-colored neck and dark cap, usually in a crouched position, partly concealed in vegetation, waiting patiently for prey. In flight it’s easy to misidentify, since it looks like an awkward crow with broad wings, neck tucked in, and legs extending just beyond the tail. At roughly 18 inches long with a 26-inch wingspan, green herons are much smaller than great blue herons, with a dark gray-green back and brown neck.
Sound is often the giveaway before sight is. Birders describe the alarm call as a sharp “skeiw!”, while the Audubon Field Guide notes a lone bird will often flush ahead of an observer crying ‘kyow’ as it flies up the creek. During courtship, the male’s legs turn orange, a small but useful clue for telling breeding adults apart from non-breeding birds and juveniles.
What makes the green heron genuinely remarkable is its hunting method. Most herons wait and strike, but green herons are one of the few bird species known to use tools. According to Outdoor Alabama’s wildlife profile, this heron has developed an unusual trait to use tools when hunting — it will drop small sticks, insects, worms and even feathers onto the surface of water to lure small fish into striking distance.
That patience pays off across a varied menu; the species is known to eat leeches, earthworms, dragonflies, damselflies, waterbugs, grasshoppers, spiders, crayfish, prawns, mice, other rodents, lizards, tadpoles, and snakes, in addition to small fish. Anyone tracking the insect side of that diet in Maine specifically might also want to look at the state’s caterpillar species or amphibian prey like the frogs found across Maine, both of which show up on a green heron’s plate.
Green herons favor a narrower slice of habitat than their larger cousins. The Audubon Field Guide lists their preferred habitat as coasts and shorelines, forests and woodlands, freshwater wetlands, lakes, ponds, and rivers, and saltwater wetlands, and classifies the species as Least Concern under the IUCN. That’s a notably better outlook than either of Maine’s other common herons, largely because green herons tolerate smaller, scattered wetlands rather than depending on large colony sites.
3. Black-crowned Night-Heron
The black-crowned night-heron (Nycticorax nycticorax) carries a name that explains almost everything about it. As Maine’s Heron Observation Network puts it, the scientific name translates to “night raven” and is appropriate considering its nocturnal habits and its crow-like call. Physically, it’s a compact bird: compared to great blue herons, black-crowned night-herons are considerably smaller and stockier with shorter legs and neck.
Adults are distinctive once you know what to look for. They show a black crown, bill, and upper back, gray wings and tail, white underparts, white plumes coming off the back of the head, and red eyes. Breeding season brings a subtle color shift, too: their legs turn from yellow to pink and the lore darkens to black, and during courtship displays the birds erect their white head plumes, which are up to 10 inches long.
Juveniles are brown, which can make them easy to overlook among marsh grasses. Anyone comparing this species to Maine’s other nocturnal hunters might enjoy a look at the state’s owl species, since both groups rely on similar low-light adaptations to hunt after dark.
| Trait | Great Blue Heron | Green Heron | Black-crowned Night-Heron |
|---|---|---|---|
| Approximate Height/Length | 2–3 feet tall, ~6-foot wingspan | ~18 inches long, 26-inch wingspan | Smaller and stockier than great blue heron |
| Coloring | Blue-gray with black eye stripe | Blue-green back, rusty neck, dark cap | Black crown and back, gray wings, white underparts |
| Most Active | Day, tied to tides in coastal areas | Dawn and dusk | Dusk through night |
| Maine Conservation Status | Special Concern | Not state-listed | Endangered |
That last row is the most urgent part of this bird’s story. Maine’s own fact sheet notes that the black-crowned night-heron has also experienced a decline in Maine over the past 30-40 years, and its limited nesting distribution and small population warranted its designation as an Endangered species under the Maine Endangered Species Act in 2015. It shares that Endangered listing with a small group of other freshwater marsh specialists, including the least bittern, the black tern, and the sedge wren.
Despite the decline, the species isn’t rare worldwide — it’s just hard to catch in the act locally. Bird Watching HQ points out that black-crowned night-herons are common in wetlands across Maine, and are in fact the most widespread heron in the world, but they are often hard to actually locate and see.
That’s because they are most active at dusk and during the evening, and while the sun is out, they spend the day hiding amongst brush and vegetation near the water’s edge. The night shift isn’t just about avoiding people; by foraging at night, these birds avoid competition from other heron species. When one does feel threatened, it announces itself with a loud, barking “quawk.”
Pro Tip: Because black-crowned night-herons roost communally by day, scan dense shrubs and low tree cover at the edge of marshes rather than open water if you’re trying to spot one before dusk.
Wetland predators tend to overlap in the same habitat, and night-herons share their marshes with plenty of other opportunistic hunters. Readers researching what else lurks in the same cattails might check out Maine’s snake species, several of which favor the same damp, vegetated edges that night-herons use for cover during daylight hours.
Good heron-watching in Maine often comes down to picking the right stretch of water. A few reliable habitat types to check include:
- Tidal mudflats and coastal bays at low tide, favored by great blue herons
- Beaver flowages and freshwater marshes with standing dead trees for nesting
- Slow rivers with overhanging vegetation, where green herons and night-herons both hide during the day
- Small ponds with dense shoreline brush, especially around dawn and dusk
The Kennebec River corridor is a good example of this layering in action. One birder’s account from Gardiner describes great blue heron and great egrets along the Kennebec River during the “wandering” season for herons, with multiple wading species using the same stretch of muddy shoreline at once. Similar wetland patterns show up in California’s heron habitats, even though the specific mix of species differs by region.
Maine’s three most familiar herons offer a useful lesson in how much variety exists within one bird family. The great blue heron hunts by day and depends on tidal rhythms, the green heron works the shadows at the water’s edge with a hunting trick most birds never learn, and the black-crowned night-heron waits until dark to avoid its own relatives.
Two of the three face real population pressure, which makes casual sightings worth reporting to programs like the Heron Observation Network. Anyone building out a broader Maine wildlife list can pair these heron notes with the state’s owls and other wetland species for a fuller picture of what shares the same marshes after dark.