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Edging Toward a ‘Life List’ of 10,000, Leading Birder Flies High

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Retired Foreign Service officer Peter Kaestner ’75, BA ’76, holds the world record for viewing the most species

Editor's note: In early February 2024, about six months after this story originally ran, Kaester achieved his goal with the viewing of his 10,000th bird—an orange-tufted spiderhunter—during a trip to the Philippines.

By Lindsay Lennon

Early in his career as a U.S. diplomat, avid birder Peter Kaestner ’75, BA ’76, arranged to spend a day off when he was on an assignment abroad. He visited a tiny South Pacific island, where he set out to observe the Kolombangara leaf warbler.

The expedition turned harrowing: after losing his way, he spent two days alone on a volcanic mountain, with no warbler to show for it.

While grateful to survive, Kaestner was disappointed to miss his quarry. But he returned months later—this time, with a guide and camping gear—and finally added the warbler to his “life list,” the term of art for the number of bird species a person has observed.

Now—with a life list of more than 9,800 species—Kaestner officially holds the world record in birding. But he won’t rest until he has met his personal goal of 10,000.

A man on a nature trail holding sound recording gear
Recording Congo forest birds while serving in the Peace Corps in Zaire. (Arnold Small)

“I love numbers—I’m wacko about numbers,” admits Kaestner, speaking from his home in the Baltimore suburbs, a Carolina wren chirping outside. “I just kept plugging away, seeing as many birds as I could, and it’s only been in the last decade or so that I realized I was close enough to the leaders that I had a chance of competing to be number one.”

How do serious birders like Kaestner document their observations and officially add “lifers” (new species) to their lists?

While Kaestner explains that supporting evidence—like photos, audio recordings, and written documentation—is helpful, a birder’s established track record largely determines the validity of their sightings.

And until recently, he notes, observing 10,000 bird species wasn’t even possible.

A man with a bird on his hand
With a yellow-billed hornbill in Namibia.

Back when he was a bio major in Arts & Sciences, there were fewer than 9,000 officially recognized species.

With advances in the science of taxonomy and increased knowledge about the birds, though, the number now tops 11,000. But those very advances also mean that Kaestner’s list is perpetually in flux.

When a scientific finding results in the combining of two species, Kaestner loses a lifer. When scientists split existing species into new ones—and he has already documented seeing them—he gains lifers.

Happily, he says, the latter happens far more often than the former. (Additionally, when entirely new species are discovered, the number of potential entries to his list increases.)

Jessie Williamson, a current postdoc with the Lab of Ornithology, accompanied Kaestner on a South American birding expedition in summer 2021, chronicling their journey in an in-depth profile of Kaestner for Outside magazine.

“Joining the big-lister club requires tremendous sacrifice,” Williamson observes in the piece, published in May 2023.

“Fewer than 60 people have ever seen more than 8,000 bird species, and fewer than 20 have gotten above 9,000. It demands exceptional, almost singular, devotion to the pursuit, often to the point of forsaking family, friends, hobbies, and a ‘normal’ life.”

I just kept plugging away, seeing as many birds as I could.

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A birder since early childhood, Kaestner seriously contemplated a career in ornithology—but rather than formally studying our avian friends, he ultimately decided to see as many as he could.

Seeking a career that would allow him to spend significant time overseas, he entered the Foreign Service in 1980 (and prior to that, he served with the Peace Corps in Africa, where he notched some 1,500 species).

Early on, the tallies were easier to come by; he birded wherever work took him and his wife, a fellow Foreign Service officer. During the couple’s time in Colombia, he even discovered a new species: a small brown bird dubbed the Cundinamarca antpitta (Grallaria kaestneri).

A man with a large white bird flying over his head
A sooty tern overhead in Australia.

As he and his wife raised two children and he grew more senior within the Foreign Service, birding inevitably took a back seat. But he added to his list wherever he could, in addition to leading hundreds of bird walks all over the world.

“I try very hard, and I’ve tried all my life, to focus my birding on lifers,” he reflects, “and when I’m not getting lifers, doing normal things.”

In addition to having the largest life list, Kaestner holds another world record: in 1986, he became the first person to observe an example of every bird family in the wild (at the time, there were 159)—a feat he achieved when he saw the rufous gnateater (Conopophaga lineata) in South America.

A person walking through a college campus
As a bio major on the Hill in the 1970s.

Since his retirement in 2016, his life list has continued to grow, through trips to places like Indonesia, Vietnam, the Philippines, and—as chronicled in Williamson’s Outside story—Peru.

Those expeditions aren’t what most people would consider relaxing getaways. As Williamson notes: during the six days she spent with Kaestner, they logged more than 1,500 miles of driving (plus two flights) in search of 12 rare birds, often skipping meals and sleeping only a few hours a night.

“Kaestner doesn’t waste time,” she observes, “and age hasn’t slowed him down.”

Top: Kaestner birding in Angola’s Tundavala Gap. All images provided (unless indicated).

Published July 26, 2023; updated March 15, 2024


  1. Jeff Hopkins, Class of 1982

    I actually birded with Peter in China back in 2010. He had one specific target: Chinese Crested Tern. I, on the other hand, was open to seeing anything.

    I wound up getting 5 lifers. Unfortunately, we both missed the tern.

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