Search for Lost Birds shows that “extinction” is not always forever

Surprisingly often “lost” means just very scarce or very well hidden

            ITHACA,  New York––The dodo,  the moa,  the passenger pigeon,  the ivory-billed woodpecker,  and the Carolina parakeet are all out of luck,  but the “Search for Lost Birds” conducted by the Cornell Laboratory of Ornithology since 2022 has brought 21 species back from the presumed dead,  confirming just six extinctions.

“The Search for Lost Birds uses a ten-year time frame to determine which species qualify as lost,”  explains the “Lost Birds” web site maintained by John C. Mittermeier,  Alex J. Berryman,  and Cullen Hanks,  “which means that new species can potentially cycle onto the list each year.

Not seen in 10 years qualifies as lost

“For 2026,  any bird species that does not have a documented record [of confirmed existence] since January 1, 2016 now qualifies as lost.

“Along with being rediscovered in the field,”  the “Lost Birds” website adds,  “species can also leave the lost birds list by being declared extinct or because they are no longer recognized as species.

“This means that updates to the International Union for the Conservation of Nature ‘Red List,’ as well as taxonomic revisions in the eBird and BirdLife taxonomic checklists,  impact which birds qualify as lost.”

The slender-billed curlew,  native to North Africa,  in 2025 became “the sixth Lost Bird to be listed as Extinct,”  by the International Union for the Conservation of Nature,  “since the ‘Search for Lost Birds’ began,  according to the website.

“Meanwhile,”  the web site continues,  “one lost bird is no longer recognized as a species.

“With five rediscoveries,  one extinction,  and one taxonomic change,  a total of seven species were removed from the ‘Lost Birds’ list in 2025,”  the website continues.

121 “lost birds” among 11,000 species

“Counting the six new lost birds,”  qualifying for addition for the first time in 2026,  “there were 121 lost birds as of January 1,  2026.

“For anyone keeping tabs on overall progress,”  the ‘Lost Birds’ website concludes,  “the initial list of lost birds that was published in 2022 included 142 species.  That dropped to 126 in 2024,  122 in 2025,  and now 121.”

According to International Union for the Conservation of Nature data,  there are currently about 11,000 living bird species,  of whom 1,480 bird species are considered to be at risk of extinction,  with 223 bird species critically endangered.

Remote islands

The critically endangered bird species live almost entirely on remote islands,  primarily in Oceania,  defined as the vast geographical region encompassing Australia,  New Zealand, Papua New Guinea,  and thousands of Pacific islands divided into Melanesia,  Micronesia, and Polynesia,  belonging to 14 different nations,  yet with a cumulative human population of just 52 million––about the same as the total human population of California,  Oregon,  and Washington,  or the population of New York state plus New England.

In view of the inherent fragility of remote island habitats,  and the low numbers of “Lost Birds” rediscovered as living,  the relatively rapid reduction in presumed avian extinctions scarcely means that these birds are not still at grave risk,  warranting protection.

At the same time,  the bird rediscoveries,  combined with a comparable pace of rediscoveries of mammals and insects previously thought to be extinct,  suggest that projections of an “extinction crisis” amplified with increasing urgency since the first International Union for the Conservation of Nature “Red List” was published in 1964 have been much exaggerated.

Extinctions:  one gone,  two back

Recent developments in mammal extinction include both confirmation of the loss of the Christmas Island shrew,  last seen in 1958 and 1984,  and the rediscovery of two marsupials native to New Guinea––the pygmy long-fingered possum and the ring-tailed glider,  both known only from the fossil record and both thought to have been extinct for thousands of years.

Recent developments in mass extinction research call into question the relationship between authentic great extinctions and episodes of accelerated evolution in response to changing circumstance.

Wrote Taylor Mitchell Brown on March 13,  2026 for Science.org,  “About 570 million years ago,  life was confined to the seas.  Large,  strangely shaped invertebrates attached themselves to the sea floor,  their fleshy fronds collecting nutrients that drifted by. These bizarre life forms, known as the Ediacaran biota,  eventually disappeared.  But researchers have long debated whether their die-off was truly cataclysmic.

“Biggest burst of evolution”

“New research published in January in Geology,”  Brown summarized,  “now offers a reappraisal of the extinction that claimed many of these creatures, known as the Kotlin Crisis—and reveals that it may have been far more extensive than previously thought,  extinguishing a similar percentage of species as the asteroid-driven calamity that killed the dinosaurs 66 million years ago.”

That would be around 80%.

Then,  wrote Tom Hale for IFL Science,  came “the Cambrian explosion,  the biggest burst of evolution to ever happen in the history of the Earth.”

Discovery of the magnitude of the Kotlin Crisis came after several years of scientific reappraisal of just what defines an extinction event.

Wrote Charles R. Marshall for Cambridge Prisms: Extinction  Volume 1,  published by Cambridge University Press in January 2023,  “Over 40 years ago,  Raup and Sepkoski identified five episodes of elevated extinction in the marine fossil record that were thought to be statistically distinct,  thus warranting the term the ‘Big Five’ mass extinctions.

“Since then, the term has become part of standard vocabulary,  especially with the naming of the current biodiversity crisis as the ‘sixth mass extinction.’

What is a mass extinction?

“However,”  Marshall pointed out,  “there is no general agreement on which time intervals should be viewed as mass extinctions,  in part because the Big Five turn out not to be statistically distinct from background rates of extinction,  and in part,  because other intervals of time have even higher extinction rates,  in the Cambrian and early Ordovician (about 480 million years ago).

“As for the current biodiversity crisis,”  Marshall said,  echoing conventional belief at the time,  “there is no doubt that the rate of extinction is among the highest ever experienced by the biosphere,  perhaps the second highest after the end-Cretaceous bolide impact.

“However (and fortunately),”  Marshall noted,  “the absolute number of extinctions is still relatively small – there is still time to prevent this becoming a genuine mass extinction.

“Given the arbitrariness of calling out the Big Five,  perhaps the current crisis should be called the ‘incipient Anthropocene mass extinction,'”  Marshall suggested,  “rather than the ‘sixth mass extinction.’”

Real-time assessments

What in truth is underway in the present are the first real-time assessments of biodiversity in the history of life on earth,  in which trends involving both some of the smallest organisms and some of the largest can be quantified from living organisms,  not just whatever happened to fossilize and be discoverable as fossils many millions of years later.

Two and a half years of scientific discussion later,  editorialized New Scientist on June 4,  2025,  “Mass extinctions are devastating events – there is no precise definition, but these are broadly understood as leading to the loss of about 75% of all species on Earth over the course of at least several thousand years.  And yet, some people argue that stopping one is easy.

“That is because, while humanity has certainly caused catastrophic biodiversity loss, even if extinction rates remain as high as they are today,  it would take us centuries to wipe out three-quarters of species.

0.2% vs. 75%

“According to John Wiens at the University of Arizona and others,”  New Scientist said,
“avoiding a textbook extinction could still be devastating.  ‘We could lose half the species on the planet over the next 3,000 years and still say,  ‘Yeah, we did it!  We prevented the sixth mass extinction,'” Wiens says.

Wiens,  New Scientist continues,  “argues that we should aim to prevent human-induced extinction from hitting 0.2% of species – a far cry from the 75% needed to qualify for a mass extinction,”  and at that,  far from likely to occur.

Currently,  about 2.1 million species have been scientifically identified,  including about a million insects,  300,000 to 400,000 plants,  and circa 360,000 animals other than insects.

About 900 total extinctions have been documented as having occurred within the past 500 years,  which appears to be the highest rate of extinction during the 300,000 years that humans have existed.

Micro-organisms

Higher estimates of extinction rates depend entirely on hypothesized huge numbers of species yet to be discovered,  most of them micro-organisms,  and high rates of extinction occurring among them,  which because these species have never been found or quantified,  has also never actually been demonstrated.

What is known is that an average of as many as 16,000 new species per year,  mostly micro-organisms,  have been scientifically described in recent years,  most of them relatively rare,  because most common species have already been identified.

Rarity in the case of large charismatic megafauna,  meaning animals easily seen and recognized,  is a predictor of extinction risk.

But rarity in the case of micro-organisms,  even the rarest of which exist in the multi-millions,  may simply reflect the diversity of life,  with multi-millions of habitat niches for new species to evolve into.

Humans, cattle, sheep & pigs

Also to be considered is the tendency of humans to over-estimate our own importance in the scheme of life,  a tendency evident at least as early as the story of Noah,  when supposedly unspecified human sins persuaded God to destroy the world,  only Noah and his family excepted.

A typical example is widespread alarm responding to a December 2025 study by Lior Greenspoon,  a Ph.D. candidate in the Department of Plant & Environmental Sciences at the Weizmann Institute of Science,  who estimated that humans and livestock,  mostly cattle,  sheep,  and pigs,  make up about 95% of the world’s mammal biomass.

But fish and marine arthropods each make up close to half of all animal biomass.  Fish alone constitute about 10 times the biomass of humans.

Mezozoic comparison

And humans,  cattle,  sheep,  and pigs are all near the extreme end of the size range for mammals,  though well short of the size of elephants and whales.

A far more lopsided concentration of biomass among relatively few species occurred during the Mesozoic era,  from 252 to 66 million years ago,  the age of dinosaurs,  when gigantic herbivores including the sauropods,  ceratopsians,  and hadrosaurs constituted as much as 70% of the biomass of terrestrial animals.

That epoch did conclude with a demonstrable mass extinction.  But it took an extraterrestrial force to bring it about,  after 186 million years of slow-paced evolution as usual.

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