Birding Controversy: Two Birders Claim 10,000 Species Record on the Same Day

In early February, 70-year-old Peter Kaestner announced he had broken birdwatching’s most mind-boggling record. He had just observed his 10,000th species.

Then shockingly, Kaestner discovered that he had been pipped to the post. Another birder, an almost complete unknown in the community until uploading a life list of some 9,000 species in October 2023, claimed to have spotted his 10,000th species just a few hours before.

Raised eyebrows

Birding is a hobby that people pursue in different ways. Those who track their sightings and search for rare birds, like Kaestner, are sometimes called “listers.” Listers typically use websites like eBird or iGotTerra to track their sightings and “life lists.” These public websites feature leaderboards that foster competition, but they don’t do much to check the veracity of sightings. Largely, birders/listers operate on trust.

So when Jason Mann bulk uploaded his life list of over 9,000 birds and then rapidly accelerated toward the magical 10,000 threshold, it raised some eyebrows. While Kaestner was well known in the lister community, publicizing his findings online over many years, no one seemed to know Mann. When Mann announced he had seen his 10,000th species just a few hours before Kaestner, people understandably found it hard to believe.

Orange-Tufted spiderhunter

This photo of an orange-tufted spiderhunter marked Kaestner’s 10,000th bird species. Photo: Peter Kaestner


The online community began to examine both men’s lists in-depth. A particularly spirited discussion broke out on the Bird Forum website. The thread is at over 430 posts and still going strong.

The luckiest birder in the world, or something fishy?

Perhaps inevitably, there were a few species on both men’s lists that provoked skepticism. But Mann’s list had by far the most questionable species. He had included some birds that people had not observed in decades, such as the New Caledonian Nightjar, a species seen only once, in 1939. Mann’s list also had far less documentation to support each sighting when compared with Katesner’s substantial online footprint over many years.

In light of a few inaccuracies spotted in his life list, Kaestner trimmed his list by a couple of species but remained above 10,000 as he continued to travel and bird watch.

The furor must have reached Mann, who eventually posted on Bird Forum and conceded defeat.

“Clearly, I made some errors when inputting my sightings into iGoTerra. New Caledonian Nightjar, for example. I’m not sure how that happened…[I] recognize that in haste there were a few oversights,” Mann wrote. “I think it best to put my support behind Peter [Kaestner] as the first birder to 10,000.”

Peter Kaestner

Peter Kaestner marks his 10,000th species. Photo: Peter Kaestner


However, Mann, an American doctor living in Hong Kong, stands by the majority of his list. At close to 10,000 birds, it would be a remarkable achievement, not least because of his obscurity in a close-knit community of “big listers.”

The IOC World Bird List contains a total of 11,194 species, so both Mann and Kaestner’s figures represent roughly 90% of the world’s species.

Martin Walsh

Martin Walsh is a writer and editor for ExplorersWeb.

Martin has been writing about adventure travel and exploration for over five years.

Martin spent most of the last 15 years backpacking the world on a shoestring budget. Whether it was hitchhiking through Syria, getting strangled in Kyrgyzstan, touring Cambodia’s medical facilities with an exceedingly painful giant venomous centipede bite, chewing khat in Ethiopia, or narrowly avoiding various toilet-related accidents in rural China, so far, Martin has just about survived his decision making.

Based in Da Lat, Vietnam, Martin can be found out in the jungle trying to avoid leeches while chasing monkeys.