While many birds specialize in cheerful-sounding song, others conjure strange and somber moods. Owls, of course, are the usual suspects when we think of the eerie bird sounds. And while it's true that their nighttime shrieks have inspired terror since antiquity, they're hardly the only birds capable of providing chills.

So which is the the most frightening? That is a decision readers will need to make for themselves. To help, we've collected six of the spookiest bird vocalizations in the Americas, combining classic notes of terror — including those of a certain quoted bird — with lesser-known, but no less startling calls.

Barn Owl

Barn Owl. Photo by Sandra Standridge/Shutterstock

Unlike most owls, Barn Owls don't engage in mellow nighttime “hooting;” they pierce the darkness with long, harsh screeches. Although both males and females can produce these shrieking sounds, they're most often made by males during flight.

Barn Owls are found throughout much of the world, including England, where Shakespeare, captivated by the owl and its shrill cries, referenced it in several plays, typically in less than cheery terms, such as: “Bring forth that fatal screech-owl to our house/That nothing sung but death to us and ours.”

These days, however, humans are the ones delivering fatal tidings. Barn Owls' low-flying hunting habits put them at risk when crossing roads, and car collisions take a constant toll. In addition, large-scale, mechanized agriculture makes large swaths of former habitat inhospitable to Barn Owls. Although their secretive nature makes accurate population counts difficult, their numbers are believed to be stable.

Common Potoo

Common Potoo. Photo by Fabio Maffei/Shutterstock

Given the Common Potoo's comically strange, almost frog-like appearance, you might expect to hear a series of monstrous croaks. But this bird holds a few surprises. Not only can it carry a note, but its slow, mournful song may be one of the most haunting in the bird world.

That's not all: Potoos' upper eyelids have several small slits that serve as “peek-holes” during the day. This adaptation allows the birds to keep an eye on potential threats while remaining still, with their enormous eyes closed.

Although considered common and widely distributed in Central and South America, Common Potoos are suspected to be in decline due to ongoing habitat loss. This nocturnal forager can be found at several ABC-supported reserves, including Tapichalaca in Ecuador, Abra Patricia in Peru, Barba Azul in Bolivia, and El Dorado in Colombia.

Common Raven

Common Raven. Photo by Manja/Shutterstock

Although most famously associated with a single word, “nevermore,” Common Ravens possess more than a little vocal dexterity. These social birds have been observed making more than 30 different sounds. Of course, none is better known than their guttural croaking, which can be heard more than a mile away.

Ironically, this iconic call may have been largely absent from the landscape Edgar Allen Poe knew when he penned “The Raven” in 1845. At that time, ravens had nearly disappeared from the eastern U.S., as its forests were rapidly felled. But as forests have returned, so have ravens. In fact, in many areas, their population is now on the rise.

In recent years, interest in these birds has grown beyond their spooky calls and appearance, as researchers have come to appreciate their remarkable intelligence. Ravens, it turns out, enjoy a level of cognition comparable with some great apes. Some studies even suggest that they can plan tasks in advance — a skill that was once believed to be exclusively human.

Common Loon

Common Loon. Photo by Jim Cumming/Shutterstock

Few bird sounds are as mournful or memorable as the Common Loon's winter wail. This eerie, howling sound, which is more than a little wolf-like, is used by both males and females to announce their presence and locate other loons.

Common Loons breed throughout much of Canada and northern areas of the U.S. Although their population is considered stable, they've suffered regional declines in the Midwest and New England. Threats include water pollution (principally due to mercury buildup in the lakes they inhabit), lead poisoning from ingested fishing sinkers, and drowning by commercial fishing nets.

Turkey Vulture

Turkey Vulture. Photo by Andaman/Shutterstock

With a distinctly skull-like head rumpled in skin the color of raw meat, the Turkey Vulture looks — at least from the shoulders up — straight out of a horror film. And its dietary preferences don't disappoint. Turkey Vultures feed on the dead, i.e., carrion, thanks to an immune system powerful enough to ward off botulism, anthrax, or salmonella.

Unable to sing, Turkey Vultures produce a gruesome hiss when agitated or fighting for better access to a carcass.

During breeding season, Turkey Vultures can be found throughout much of the U.S. They occur year round in southern states, and are found all the way down to South America. Although threatened by pesticides several decades ago, their numbers are now on the rise and they are one of the most common large carnivorous birds in the United States.

Barred Owl

Barred Owl. Photo by Dennis W. Donohue/Shutterstock

Barred Owls are typically identified by their rhythmic “who-cooks-for-you” hoots, but all bets are off during courtship, when these nocturnal hunters produce a cacophony of shrieks, caws, and gurgles with haunting effect.

Historically, Barred Owls were found in the eastern U.S. However, during the 20th century, fire suppression in the boreal forest and tree planting on the Great Plains allowed these birds to expand their range. Their population has slowly increased over the last 50 years.

Because Barred Owls nest in large dead trees, they're often found in mature forests, and their presence is used an indicator of forest health in some places. Logging can pose a localized threat to these owls.