We all would recognize a double-crested cormorant if we saw one.

Most notably, these long-necked diving birds are often seen standing on docks, jetties or stone outcroppings, spreading their wings to help dry their feathers.

“Though they look like a combination of a goose and a loon, they are relatives of frigatebirds and boobies and are a common sight around fresh and salt water across North America,” adds The Cornell Lab of Ornithology’s website, allaboutbirds.org.

Double-crested cormorants get their name from tiny tufts or feathered “crests” on each side of their head that are visible during mating season.

What’s not well-known, however, is the double-crested cormorant and its larger cousin, the great cormorant, who both inhabit Connecticut’s coastal waters, are master hunters.

“Cormorants are believed to be the most efficient marine predators in the world, catching more fish per unit of effort, on average, than any other animal,” writes David Allen Sibley in his new book, “What It’s Like To Be A Bird.”

Why are cormorants so effective?

First, they have large, webbed feet, giving them exceptional propulsion under water. Second, cormorant feathers, unlike duck feathers, retain just the right amount of water so that it doesn’t reach their skin, yet reduces their buoyancy by about 20 percent. And that’s the advantage, according to Sibley, that gives cormorants the speed and agility to capture small fish and crustaceans so effectively.

Cool facts:

* When cormorants catch a crustacean, like a crayfish, they exhibit a little flair in eating it — hammering the prey on the water to shake its legs off, then flipping it in the air and catching it headfirst for easy swallowing, notes allaboutbirds.org.

* Because cormorants do not have as much preening oil as ducks, and their feathers retain water, these unique seabirds must get out of the water about every 20 minutes or so and dry their wings.

* The oldest known double-crested cormorant that lived in the wild was 22 years and eight months old.

How do you tell the difference between double-crested cormorants and great cormorants?

The double-crested cormorant is the smaller of the two, sporting a bit of orange-yellow skin around the base of its bill, while the great cormorant has a heavier bill and a “pale yellow chin pouch, bordered by a white throat strap,” writes Roger Tory Peterson in his classic “Eastern Birds” field guide.

Sadly, cormorants are incorrectly blamed for not only being an invasive species, but depleting fish stocks.

For example, in a recent letter to the city editor of The Day, titled “Less cormorants equal an improved environment for all citizens,” one writer claims, “Cormorants were brought from Asia to the West Coast of the United States over 175 years ago.”

Stop right there. I recognize these are editorial comments, and everybody is entitled to their own opinion, but please, get your facts straight. Cormorants are not an invasive species. In fact, according to the U.S. Fish & Wildlife Service (USF&W), there are six native species of cormorants in North America, two of which I’ve mentioned in this article.

The writer further complains that if cormorants eat a pound of fish per day (they can eat this much) and there were 500 cormorants staying in the waters between the harbors of Niantic and Stonington for 157 days of spring, summer, and fall, they’d eat 78,500 pounds of juvenile fish.

This rationale is not science-based, nor is there any proof cormorants would eat that many “juvenile” fish in a confined area.

First, cormorants are highly mobile, mixing it up, often flying 20-30 miles or more to hunt their quarry. Second, cormorants are not picky eaters.

In fact, scientists claim cormorants eat some 250 different species of fish and crustaceans. These include sculpins, rock gunnel, pollock, cunner, mummichog, Atlantic cod, winter flounder, tautog, sandlances and capelin. So, there’s little chance that cormorants would wipe out a particular fish stock, like the coveted young stripers or snapper blues.

Indeed, Patrick Comins, executive director of The Connecticut Audubon Society, who is an expert birder, also weighed in on cormorants, noting, “The Connecticut Wildlife and Fisheries divisions do not believe they cause a problem for fish stocks.”

Enjoy bird watching!

Bill Hobbs lives in Stonington and is an avid bird watcher. He can be reached for comments at whobbs246@gmail.com