Green Heron

Butorides virescens

Old-timers will perhaps remember once calling this bird a Little Green Heron. At least, that is what it was referred to in the field guides. While there is a Great Blue Heron to go along with the Little Blue Heron, there is certainly no Great Green Heron anywhere in North America. So, the older name was confusing. It has also been called a Green-backed Heron although, depending on the light, the bird’s back does not always appear so. Still, almost any name would be better than some of the vernacular ones used. Two of these, “shitepoke” and “chalkline” refer to its habit of letting loose a stream of white excrement when flying off to avoid disturbance


So, Green Heron it is. This species is relatively common in Carroll County, even though it leaves us in the Fall when temperatures begin to drop. Some ornithologists claim that it is the most widely distributed American Heron. The Green Heron breeds throughout the Eastern United States from Canada to the Gulf of Mexico. It can also be found on the West Coast south to Central America and the West Indies.
The birds who headed south in the Fall return here in late Winter and early Spring. They will often travel in flocks. Usually this takes place under the cover of darkness. Most arrive on breeding grounds in April. Pairing may begin during migration. Couples are only seasonally monogamous, but may return to previously used sites. Males then establish and defend nesting territories, bordered by perches from which they periodically utter low pitched “skow” calls. By this time, bills of the adult birds have
changed to a glossy black. Their legs are bright orange compared to the greenish-yellow they sported earlier.
As if “skow” calls weren’t romantic enough, the two begin an elaborate courtship display which includes “exaggerated flapping, erect crest and neck plumage, bill snapping, neck stretching and swaying, bowing and hopping.” Males may sometime begin nest construction even before mating, however, it usually ends up with the female taking over and setting things right. Not to be left out of the process completely though, the male may continue to gather nest material and bring it to the female.
Even so, some Green Heron nests are nothing to get excited about. They can be either very solidly constructed or so flimsy that you can see the eggs through the bottom. The birds prefer trees with dense foliage and build between 10 and 20 feet from the ground. Nesting is often solitary, however, Green Herons may also nest in rookeries with other herons. Common Grackles also appear to be regular nesting associates. Perhaps the grackles act like a security alarm, making a racket when danger approaches.
Three to five greenish-blue eggs are laid. Both sexes take turns incubating these until they hatch in about three weeks. Feeding is also by both parents. The young birds fledge in another three weeks. One brood is the rule in northern sites. Further south, one might expect there to be two. After the breeding season, birds may wander widely.
Studies have been made of the Green Heron’s diet. 45% of this is made up of small fish. 24% may include insects with dragonflies and grasshoppers figuring prominently. Another 21% contains crayfish and other crustaceans. Then, add some snails, spiders, and earthworms for flavor. Not to mention frogs, lizards, snakes, and mice. In other words, they eat what they can get!
To make the most of the menu, Green Herons frequent brushy wetlands, swampy thickets, marshes, pond edges, and shallow ditches. They generally stay close to shore and seldom wade in water deeper than four inches, feeding both day and night. What Green Herons know about fishing could surely be a lesson to human anglers. Crouching down along the shore with their necks drawn in, they strike when hapless prey happens by. They may also rake their bills back and forth though the water waiting to see what comes out of hiding. The more adventurous birds may even dive head-first from a branch into the water, often becoming completely submerged.

Like the Black-crowned Night Heron, the Green Heron may also “bait fish”. This most fascinating behavior involves dropping a small item on the water’s surface and waiting to see what happens. The item may be a feather, an insect, a leaf, or something else easily managed. Any small fish that comes to investigate the bait, will quickly be snatched up sideways in the bird’s bill. A quick toss and it disappears head-first. Just like its human fisherman counterpart, the bird may take up the bait occasionally and modify it if it isn’t getting any bites.
Green Herons do not seem to be as long-lived as the other larger species. Eight years stands as the record. Interestingly, however, they seem less susceptible to the effects of pesticide than other water birds. The species appears to have little competition and few predators except for the usual nest robbers like snakes, crows, and raccoons. Its population and range appear to be expanding.

Carroll County Chapter of Maryland Ornithological Society

%d bloggers like this: