About the Search for Lost Birds

The Search for Lost Birds follows the definition established by Long and Rodríguez (2022; Oryx 56: 481-482): 

“a lost species is one not confirmed alive by photographic, audio or genetic information for over 10 years in the wild and has no ex situ population under human care.” 

This means that species recently seen, but not photographed, would still qualify as lost, while a bird with captive populations in zoos and aviaries would not, regardless of its status in the wild. This last caveat disqualifies birds like the Edwards's Pheasant (Lophura edwardsi) and White-naped Pheasant-pigeon (Otidiphaps aruensis), which both have populations in captivity, even though they may be 'lost in the wild.'

Defined in this way, lost species prioritize knowledge gaps over extinction risk. As a result, Lost Birds span the full range of what's known as IUCN Red List categories, from Least Concern to Critically Endangered (Possibly Extinct). Although species with a greater risk of extinction will be higher conservation priorities, every Lost Bird represents a species that would benefit from a closer look and new information.

A variety of different reasons can lead to a species becoming lost. For instance, some birds are extremely difficult to find or identify, resulting in very few detections. Others live in remote areas that are rarely visited by researchers and birdwatchers. Unfortunately, a species' lost status can also indicate that it's on the precipice of extiction, or possibly even already extinct. Grouping species according to their IUCN Red List categories provides insight into the different kinds of Lost Birds:

Critically Endangered (Possibly Extinct) -- Lost Birds in this urgent category are perilously close to extinction or may already be extinct. They are lost because of extremely small population sizes or, tragically, because they can no longer be found. This group offers the largest risk/reward ratio, but continued search effort is warranted, even though any individual search is likely to come up empty-handed. Efforts to look for these species should carefully document both the areas searched and the amount of search effort.

Endangered and Critically Endangered -- These Lost Birds have more optimistic outlooks than the previous category, but they are still highly threatened with extinction and lost for the same reasons (small populations and restricted distributions). With the right combination of preparation, perseverance, and luck, this group offers more viable routes to rediscovery. These species represent the highest search priorities on the Lost Birds List.

Near Threatened and Vulnerable -- These species are primarily lost due to a lack of recent search effort and, to a lesser degree, sparse details on their whereabouts. With a concerted effort, almost all of these species should be rediscovered, enabling us to get a better sense of their habitat quality and the current threats they face.

Least Concern -- With few exceptions, these Lost Birds occur in areas of intact habitat that are rarely visited by birdwatchers and researchers, such as isolated tepuis in Venezuela and the remote Foja Mountains in New Guinea. Assuming that the right areas can be accessed, thorough searches should encounter these species. Once found, the priority would be documenting their status so that we can learn more about their basic natural history. 

Data Deficient -- These Lost Birds are mysteries, species about which we know so little that we cannot even guess at their true conservation status. Some of these species are known only from a single specimen or, in one case, a single wing! As such, several of these birds might turn out to be hybrids or represent abnormal plumages of more common species. Before setting out to search for this subset, the best path forward is to consult museum collections and the historical record.

The Search for Lost Birds uses records from published literature, museum archives, citizen science platforms, and expert feedback to determine which species have been documented in the past decade. Citizen science platforms such as eBird, Xeno-canto, and iNaturalist are a particularly important component of this. Together these three platforms contain tens of millions of media records of birds covering more than 98% of the total bird species on earth! Submitting observations and media records to these platforms, even of bird species that are not lost, provides incredible valuable data and is a great way to help support the Search for Lost Birds and other conservation initiatives.

As many birdwatchers know, whether a bird should be a species or a subspecies can depend on who you ask. The Search for Lost Birds focuses on birds that are considered species according to either the eBird/Clements checklist or the BirdLife International checklist. We selected these two taxonomies because they integrate with the largest citizen science database for birds (eBird) and the Red List of Threatened Species (BirdLife). Most Lost Birds list are considered species by both eBird and BirdLife, but in a few cases they differ. For example: the Creamy-breasted Fig-Parrot is considered a distinct species by BirdLife but a subspecies of Orange-breasted Fig-Parrot by eBird. Meanwhile, the Manus Masked Owl is considered a species by eBird but a subspecies of Australian Masked-Owl by BirdLife. For our purposes, both Creamy-breasted Fig-Parrot and Manus Masked-Owl are  Lost Birds. In an effort to minimize confusing names, we use the eBird species name except when a species is only considered a species by BirdLife, in which case we use the BirdLife name. So the list of Lost Birds lists “Creamy-breasted Fig-Parrot” (following the BirdLife name for a BirdLife-only species) and “Manus Masked-Owl” (an eBird-only species). 

The Search for Lost Birds is a collaboration between American Bird Conservancy, Re:wild, and BirdLife International and is supported by Birds of the World.

American Bird Conservancy is a nonprofit organization dedicated to conserving wild birds and their habitats throughout the Americas. With an emphasis on achieving results and working in partnership, we take on the greatest problems facing birds today, innovating and building on rapid advancements in science to halt extinctions, protect habitats, eliminate threats, and build capacity for bird conservation. Find us on abcbirds.org, Facebook, Instagram, and Twitter (@ABCbirds).

Re:wild protects and restores the wild. We have a singular and powerful focus: the wild as the most effective solution to the interconnected climate, biodiversity and human wellbeing crises. Founded by a group of renowned conservation scientists together with Leonardo DiCaprio, Re:wild is a force multiplier that brings together Indigenous peoples, local communities, influential leaders, nongovernmental organizations, governments, companies and the public to protect and rewild at the scale and speed we need.

BirdLife International is the world’s largest nature conservation Partnership: a global family of over 115 national NGOs covering all continents, landscapes and seascapes. BirdLife is driven by its belief that local people, working for nature in their own places but connected nationally and internationally through the global Partnership, are the key to sustaining all life on this planet. This unique local-to-global approach delivers high impact and long-term conservation for the benefit of nature and people.

Please cite the Lost Birds List as: Search for Lost Birds. 2024. A global list of lost bird species, version 2. Accessed from: www.searchforlostbirds.org on [date].