On an average morning, Susan Glass can sit on the patio at her condominium complex in Saratoga, Calif., and identify as many as 15 different Bird species by ear: a steller’s jay, an acorn woodpecker, an oak titmouse.

For her, Birding is more than a hobby. “Birds are my eyesight,” said Ms. Glass, a poet and a professor of English at West Valley Community College who has been blind since birth. “When I check into a hotel in Pittsburgh, I might remember the rock dove and the house finch in the parking lot, rather than the architecture.”

Mnemonics are used by many birders to help identify bird calls. Some are more clear than others. The eastern towhee sounds like it’s saying “Drink yer teeeeea!” Audio via Michael Hurben

Ms. Glass, 67, was a child when she first noticed the birds twittering outside her family’s home on the Lake Erie coast of Michigan. “My mother told me they were a swallow called the purple martin,” she said. “I was paying attention to where they were flying, and I could actually start to hear the dimensions of our little cabin, the screen porch, the front yard.”

She has mapped her surroundings by bird song ever since.

Birding got a significant boost with the pandemic: With so many people doing less, they tuned in to the sounds of nature more; and with lockdowns came a reduction in noise pollution, which made the bird calls all the more pronounced.

Sarah Courchesne, a Massachusetts Audubon program ornithologist in Newburyport, attributes the increased interest in birding partly to the fact that it’s a way for people of all abilities to tap into nature — whether by eye, by ear or both.

As the birding community grows larger and more diverse, Ms. Courchesne said, birding clubs and conservation organizations are thinking more about accessibility, and this is changing the way they talk about birding and think about it.

For one thing, the terminology is evolving. According to Freya McGregor, a 35-year-old birder and occupational therapist specializing in blindness and low vision, the term “birder” was once reserved for those who were more serious than the hobbyist “bird watcher.” But increasingly, “birder” is becoming a catchall, thanks to a growing awareness that some hobbyists identify birds not by watching, but exclusively by listening.

Spaces are evolving too. Nature trails from Cape Cod to the Colombian Andes are being reimagined, with features like wheelchair-accessible terrain and guardrails to guide guests with low vision. The Audubon Society in Massachusetts recently introduced a series of All Person’s Trails, which are designed for accessibility.

Public programming is also expanding. Birding organizations across the country are introducing a new kind of bird “walk” — one called a “big sit,” where you just stay put. These stationary birding events, popularized by the New Haven Birding Club in the early 1990s, is a type of competitive event, sometimes hosted as a fund-raiser, in which teams of birders stay within their own 17-foot-diameter circles for a 24-hour period and identify as many birds as possible.

Early ornithologists attempted to describe the rhythmic phrases of the American robin’s cheerful song with words like “Cheer up, cheerily.” Audio via Jerry Berrier

In May, Ms. Courchesne hosted a big sit alongside Jerry Berrier, a blind birder, on an All Person’s Trail near Ipswich, Mass. Mr. Berrier, who lives in Malden, Mass., said he wanted his event to be less competitive and more meditative than a traditional bird sit.

While some studies have shown that simply hearing bird song may alleviate anxiety and boost feelings of well-being, Mr. Berrier, 70, said the benefits go beyond that for him. “Birding gives me a connection with a world I can’t see,” he said, including when the world outside is waking up in the morning and winding down at dusk.

He doesn’t even need to step outside to listen. Mr. Berrier’s home is surrounded by an audio mixer and sound recording equipment — parabolic microphones and devices he has custom-made — piping in bird sounds from the outdoors in real time, and recording bird song in quieter environments.

At the Ipswich bird sit, Mr. Berrier pointed people to the resonant song of an ovenbird; the buzzy trills of various warblers and the flutelike notes of a Baltimore oriole, which sometimes sounds like it’s saying: “Here; here; come right here, dear.”

When teaching newcomers how to distinguish birds by ear, Mr. Berrier often shares mnemonics. For the eastern towhee, he said, listen for a bird that tweets: “Drink yer teeeeea.” The American robin sounds like it’s singing, “Cheer up, cheerily.” The Northern cardinal might be saying, ‘Watch here, watch here.’” American goldfinches call “potato chip” in flight, while olive-sided flycatchers chirp, “Quick! Three beers!”

One of the mnemonic phrases that Mr. Berrier and other birders use to identify the the Baltimore oriole is “Here; here; come right here, dear.” Audio via Jerry Berrier

Mr. Berrier has been birding since the 1970s, when he was in college at the Indiana University of Pennsylvania. There, a professor gave him a special assignment to replace the dissection-based portion of his biology course.

“He ended up giving me probably one of the greatest gifts that’s ever been given to me by recommending that I listen to his record albums from Cornell University that had bird sounds on them,” Mr. Berrier said. “He said, ‘I want you to listen to these during the semester, and at the end, your lab portion of the grade is going to be based on a walk in the woods with me, and I will ask you to identify some of the sounds you hear.’”

At first, Mr. Berrier found it daunting to distinguish bird species in the wild just by their sounds. “I just thought, ‘Man, these birds all sound the same,’” he said. “But by the end of the semester, I was hooked, and I’ve been doing it ever since.”

During these early outings, Mr. Berrier identified cardinals, with their laserlike trills; robins with their cheery twittering; and red-winged blackbirds, whose call he still thinks of as “a harbinger of spring.”

To some, the Northern cardinal sounds like it’s saying “pretty, pretty, pretty.” Audubon Vermont compares its call to a Star Wars light saber. Audio via Jerry Berrier

‘A Bird Heard’

For birders looking to build out their “life list” of every bird they’ve ever spotted, knowing these calls can be indispensable: The American Birding Association’s rules for identifying a bird species make no qualitative distinction between “a bird heard” and “a bird seen.”

Trevor Attenberg, a scientist and writer who is blind and lives in Portland, Ore., pointed out there are plenty of birds you have far less chance of seeing than hearing. “Something like 60 to 70 percent of the birds that you will encounter, you will only be able to encounter by ear,” Mr. Attenberg said.

“I’m always listening to what kind of birds I can hear in any given environment, whenever I step outside, and it tells me so much,” he said. “It tells me about the weather, and the seasons. It tells me about this specific landscape that I’m in. Even when I’m in urban environments, it can tell me about the quality of habitat.”

The Mexican whip-poor-will, which can be found in the southwestern U.S., has a call that sounds like its name. Audio via Michael Hurben

Learning the percentage of birds that one might only ever have a chance to identify by ear gave Mr. Attenberg, 40, more confidence. “It’s indicating to me — as the blind birder, uncertain as to my place in science — that I actually can compete with other ornithologists that can spot birds through binoculars and so forth, which I can’t really do,” he said. “Learning that, in fact, such a large share of possible bird detections are only going to come through the ear, tells me that, well, there is room for blind people — and people that just enjoy using their ears for listening or collecting information — to learn about birds in this way.”

Birders don’t need to memorize every call: Birding apps like BirdNET or the Cornell Lab of Ornithology’s Merlin Bird ID can record bird sounds in the wild and help a listener identify the species.

But the notion of “a bird heard” is becoming increasingly imperiled as noise pollution brings about fundamental changes in the way nature sounds. Ornithologists have reported birds changing the tenor of their calls as they strain to be audible over the din of human-made noise — whether it’s crypto mining or just the everyday sounds of leaf blowers or car traffic.

The barred owl seems to be asking, “Who cooks for you?” Audio via Michael Hurben

Ms. Glass, the poet in California, said she has noticed that, over time, there are fewer bird sounds altogether. “There is no longer, in my part of the world, what you would call a dawn chorus — an overwhelming bird chorus that drowns out everything else,” she said. Bird song ebbs and flows with the seasons, peaking during migrations. But studies indicate that as bird populations decline, bird song is declining, too.

5,400 Birds

Michael Hurben, 56, is on a mission to document what he can, while he can. Because of a degenerative retina disease, his field of view has narrowed over time, from 180 degrees to, he estimates, less than one-tenth of that.

So Mr. Hurben, a retired engineer who lives in Bloomington, Minn., has doubled down on his love of birding, and is well on his way to identifying 5,400 different birds — a little more than half of all bird species in the world. “I just want to be able to say that I’ve identified the majority,” he said.

He and his wife, Claire Strohmeyer, who is also 56 and a clinical researcher, have visited dozens of international destinations to check rare species off the list. But a narrow scope makes searching for a bird in a tree, or spotting it through binoculars, especially challenging.

This makes his ability to identify birds by ear indispensable. He has brushed up on his skills online, but also by birding with other birders by ear, including Mr. Berrier, who joined Mr. Hurben on a birding trip to Cape May, N.J., last year.

Mr. Hurben finds it increasingly difficult to hear certain bird song, like the very high-pitched calls of the colorful cedar waxwing.

“Before we go on a trip, I will try to really study the calls ahead of time,” he said. While some calls do require a mnemonic to remember, others are very distinctive.

The screaming piha has a call so unique it’s a go-to for sound designers when making films set in jungles, said Michael Hurben, a birder. He recorded this sound clip on a birding trip to Brazil. Audio via Michael Hurben

He cited for example, the screaming piha, a plain-looking gray bird he and his wife trekked into the Amazon to identify. Its unique call is a go-to for sound designers when making films set in jungles, he said. (Listen for it in Werner Herzog’s 1972 film, “Aguirre, Wrath of God.”) Likewise, another South American bird, the sharpbill, has a call that sounds “like a falling bomb,” Mr. Hurben said. “I hear that song once, and I’ll never forget it the rest of my life.”