Stealth, secrecy and patience – that’s the hunting mode of a green heron, one of the many avian residents of Little Swamp Sanctuary in Shepherd, Michigan.
Once called the green-backed heron, this bird has an iridescent green back that can appear blue in sunlight and black in shade. They also have long brown and white stripes on their bellies and under their necks, which easily blend into the vegetation. Green herons are able to camouflage themselves by standing still and mingling with branches, tall grass and sedges. However, they constantly wag their tails when they think people spot them.
A green heron’s call is a startling “keow” that is given when it takes flight from a disturbance. They will also make sounds similar to chickens.
The green heron is about the size of a crow, but it can stretch its neck to almost three times its size. They may look like a lollipop or popsicle when sleeping or standing on one foot with their head under a wing. They can unfold to be higher than the knee with a long neck and legs. Being a lesser known little heron, people may confuse them with a baby great blue heron.
The green heron’s eyes are located on the side of the head, one on either side of a long, pointed beak. For this reason, they have binocular vision, looking at the bill. Green herons also have peripheral vision – or side vision – which helps them watch out for predators; this is necessary because the green heron is both predator and prey.
These birds often hunt from a log or branch near shallow water. They stay very still, watching for any ripples or disturbances in the water that could be an aquatic insect, frog, or minnow. Green herons rarely stab their prey. Instead, they grab food in their beaks and then turn small fish or frogs to swallow headfirst. They sometimes rake the bottom of the pond with long toes in order to dig small aquatic creatures out of the mud. To catch their prey, they must have clean, clear water.
Hunting for underwater prey is a challenge. As water refracts light, creatures below the surface of the water appear to be at a different depth than they actually are. The heron must compensate for this illusion each time it tries to catch prey.
Green herons are among the birds that use tools. They will use bait – including sticks, feathers and insects – to attract small fish to the surface
“There was a time when it was thought that only humans used tools, and that was an ability that separated animals from humans. But herons are pretty adept at using whatever tools are available,” said Barb Rogers of the Wildlife Recovery Association, which also manages the Little Swamp Sanctuary.
In addition to clean water, green herons need wooded wetlands with branches and logs to hunt. According to Rogers, more than half of Michigan’s historic wetlands have been destroyed; even fewer forested wetlands remain, leaving only a small fraction of the green herons’ preferred habitat.
Rogers and her husband Joe usually see two baby birds that are raised in a loosely woven stick nest 20-30 feet from a tree. Green herons can nest in small colonies, but often nest alone near the edge of a wetland, pond, or stream. Parents feed their chicks for about two and a half weeks by regurgitating food. In the weeks that follow, the young follow the adults who continue to feed them and teach them basic survival skills.
The efforts of young herons are not always smooth and graceful. One day Joe heard loud splashing like something was drowning. It turned out to be a young green heron trying to catch something underwater. The bird eventually found a submerged branch to perch on, allowing its head to stay above water.
“These birds often have difficult experiences when they are out foraging and trying to mimic parent behavior,” he said.
Although green herons are fairly common, their numbers have rapidly declined over the past 55 years. According to the North American Breeding Bird Survey, the population of green herons has declined by 51% from 1966 to 2019. The Cornell Lab of Onithology states that while green herons are still too numerous or widely distributed to warrant watchlist status , they have experienced “worrying long-term declines.”
The Little Swamp Sanctuary was once home to over 90 of these little herons; now only about a third of that population remains.
“Those that remain seem to be doing well and we hope the ‘herd’ will grow over the next few years,” Rogers said.
Green herons primarily nest in wetlands and coastal areas of the United States and Mexico. They often migrate and hunt at night, but lack night vision. This makes it easier for their flight to be interrupted by new obstacles introduced into their flight paths, including tall buildings, high-voltage transmission lines, radio towers, and wind turbines.
Many years ago, the Wildlife Recovery Association accepted a nestling green heron into its rehabilitation program. He grew up quickly with small fish and easily learned to hunt for food in a large outdoor cage. They finally released the heron, which they nicknamed “Stab”, leaving the door to its enclosure open.
“We’re hoping some of the greens we see now could be his grandchildren,” Rogers said.
Wildlife Recovery Association is a 501(c)3 charitable organization dedicated to education, rehabilitation, and research to benefit wildlife, and to operate a sanctuary to protect rare and sensitive species. To donate to help these magnificent animals, visit WildlifeRecovery.org or write to Wildlife Recovery Association, 531 S. Coleman Road, Shepherd, MI 48883.
