Click on any of the following for some background and an explanation of the technical terms used in the species factsheets and additional data tables:

• IUCN Red List Categories
• IUCN Red List Criteria
• Range and country distribution
• Habitats, altitude and migratory status
• Threats and impact
• Data quality and derivation
• Extinct species 
• Red List Index
• Generation length

Extinct Species

The bird species that are treated as Extinct by BirdLife are taken from a comprehensive study undertaken by the Committee on Recently Extinct Organisms (e.g., MacPhee and Flemming 1999, Harrison and Stiassny 1999). All recently extinct bird species are treated, subject to three criteria:

1. They must have a formal name and hence be a valid taxonomic entity. Therefore four apparently distinctive but as yet undescribed Mascarene forms are discounted: a fody from Réunion and a petrel, a bulbul and a babbler from Rodrigues (Cheke 1987, Cowles 1987). The petrel is known from travelers' reports as well as subfossil bones, the bulbul and the babbler from bones only, and the fody (see Foudia bruante below) just from historical accounts (Cheke 1987, Cowles 1987).
2. They must be considered a full biological species. Knox and Walters (1994) give a list of extinct subspecies, largely based on Greenway (1967); a thorough update of this list is still required. Thus, for example, the following are discounted: Anas (platyrhynchos) oustaletti, Turnix (varia) novaecaledoniae, Halcyon (cinnamomensis) miyakoensis, Psitticula (echo) equus, Hemiphaga (novaeseelandiae) spadicea, Lalage (leucopyga) leucopyga and Acrocephalus (familiaris) familiaris, for which the prevailing published opinion is that they are valid at the subspecific level only, along with a number of other names which are almost certainly synonyms (see list of hypothetical taxa below).
3. The species must have been documented to have survived past (the admittedly arbitrary) ~AD 1500. Such documentation includes paintings and reports, which Banks et al. (1993) recognize as being valid historical types. All species known only from pre-1500 subfossils are excluded, recognizing that this excludes a number of New Zealand (Holdaway 1999), Pacific (Steadman 1995) and Hawaiian (Olson and James 1982) extinctions from the last two millennia. No moa species survived as late as 1500 (Holdaway and Jacomb 2000, contra WCMC 1992) nor Aepyornis maximus or Cygnus sumnerensis (Baillie and Groombridge 1996).

Hypothetical taxa - The following taxa have been listed as extinct in various sources, but are dubious in that they likely to be only distinct at the subspecific level, or not valid at all. Note also that three taxa described from Mauritian subfossils have been shown to belong to extant species - Anhinga nanus was in fact Phalacrocorax africanus (Olson 1975c), Circus alphonsi was in fact Circus maillardi (Cowles 1987) and Podiceps gadowi was in fact Phaeopus numenius (Rountree et al. 1952) - and that the Lesser Weka Gallirallus minor, known from a number of subfossil bones from South Island, New Zealand, is presumably a synonym of the slightly larger but otherwise identical Weka G. australis (Olson 1975b). Six taxa listed as extinct by Greenway (1967) or Balouet and Alibert (1999) without documentation are almost certainly invalid: Pterodroma hindwoodi from Norfolk Island, Australia (Jouanin and Mougin 1979), Thinornis rossi from Auckland Island, New Zealand (Peters 1934), Zenaida plumbea from Jamaica (Peters 1961), Caprimulgus ludovicianus from Ethiopia (Cleere 1999), Celeus immaculatus from Panama (Peters 1948) and Geospiza nebulosa from the Galapagos Islands, Ecuador (Paynter 1970).

Rhea nana (Dwarf Rhea) was named by Lydekker in 1894 from a single dubious egg from south Patagonia, Argentina1. 
References: 1. Knox and Walters (1994).

Megapodius stairi was named by Gray in 1861 from a single egg collected in 1847, reportedly on Nina-fou (and therefore probably a synonym of Polynesian Scrubfowl M. pritchardi), and now in Tring2. M. andersoni (reportedly from New Caledonia) and M. burnabyi (reportedly from Hapace Island, Tongatapu, Tonga) are also known only from dubious nineteenth century eggs2, as are undescribed megapodes from Lord Howe Island, Australia and Great Andaman Island, India2 and Sunday Island in the Kermadec Islands, New Zealand1. 
References: 1. Cheeseman (1890). 2. Knox and Walters (1994).

Anas (platyrhynchos) oustaletti (Marianas Mallard) was endemic to the Mariana islands of Guam, Tinian and Saipan (to U.S.A.)1 and almost certainly had its origin in hybridization between Mallard A. platyrhynchos and Grey Duck A. superciliosa2. The last record was in 1979, with its extinction a result of overhunting and wetlands drainage1. 
References: 1. Reichel and Lemke (1994). 2. Yamashina (1948).

Turnix (varia) novaecaledoniae is known from the type in the British Museum, collected on New Caledonia (to France) and described by Ogilvie-Grant in 1889, from a reported 1911 specimen taken by Sarasin, from various reports (including one that T. varia were introduced onto the island from Australia in the nineteenth century), and fossils1. Its taxonomic status is unclear1. 
References: 1. Balouet and Olson (1989).

Halcyon (cinnamominus) miyakoensis (Ryukyu Kingfisher) is only known from a single bird apparently collected on Sakishima, in the Ryukyu Islands (Nansei Shoto), Japan, in 18875 (incorrectly listed as 1841 by some sources2). Nothing is known of the taxon in life, and it is assumed to be extinct5. The holotype has red legs and may have had a red bill (its bill sheath is now missing) but is otherwise similar to Micronesian Kingfisher H. cinnamominus and some authors have considered the taxon a subspecies of this4. The validity of the holotype has also been questioned, with suggestions that it may have been a vagrant from Guam, an escaped cagebird, or mislabelled3. Maybe because of these uncertainties, the taxon was removed from the 1996 Red List1. 
References: 1. Baillie and Groombridge (1996). 2. Balouet and Alibert (1990). 3. Brazil (1991). 4. Fry et al. (1992). 5. Stattersfield et al. (1998).

Eos goodfellowi was described by Ogilvie-Grant in 1907 based on two birds brought to England alive by Goodfellow, apparently from Obi, Indonesia; they were not preserved4. Holyoak1 2 asserted that the birds were immature Red Lories E. bornea, maybe purchased on Obi, although the species does not occur there naturally3. 
References: 1. Holyoak (1970). 2. Holyoak (1976). 3. Walters (1975). 4. White and Bruce (1986).

Lorius tibialis (Blue-thighed Lory) was described by Sclater in 1871 from a bird brought to England alive by Jamrach having been bought in Calcutta market, India, apparently "from one of the less explored islands of the Molucca group," and now in Tring2. It is probably an aberrant L. domicella1. 
References: 1. Forshaw and Cooper (1989). 2. Knox and Walters (1994).

Lorius amabilis (Stresemann's Lory) was named by Stresemann in 1931 from a specimen from Nakanai, New Britain, Papua New Guinea2; it is a synonym of Purple-bellied Lory L. hypoinochrous1. 
References: 1. Forshaw (1971). 2. Knox and Walters (1994).

Loriculus salvadorii is known from Hachisuka's 1930 type in Delaware and from a female, collected by Cuming, in Tring1; there is no evidence that it is anything other than a synonym of the Mindanao, Philippines race of Colasisi Loriculus philippensis apicalis Souancé 18562. 
References: 1. Dickinson et al. (1991). 2. Peters (1961).

Psitticula (echo) equus (Réunion Parakeet) was endemic to Réunion (to France) from where it is known from a number of descriptions and paintings, but no specimens survive1. It became extinct in the early eighteenth century, presumably as a result of direct exploitation by people1. 
References: 1. Cheke (1987).

Ara erythrura was described by Rothschild from one of the West Indian islands, based on the writings of De Rochefort in 16581. 
References: 1. Rothschild (1907).

Hemiphaga (novaeseelandiae) spadicea (Norfolk Island Pigeon) was endemic to Norfolk Island (to Australia) 3, from where it is known from two skins (one now missing) in Tring2 and was last recorded in 19003. Knox and Walters2 gave it specific status but it is better treated as a subspecies of the extant New Zealand Pigeon H. novaeseelandiae1 3. 
References: 1. Garnett (1993). 2. Knox and Walters (1994). 3. Stattersfield et al. (1998).

Gymnocrex (plumbeiventris) intactus (Intact Rail) is only known from the unique type (in Tring1) collected by L. Brazier2 in the Solomon Islands and described by Sclater in 18691. However, many of Brazier's specimens reportedly from the Solomons were actually from New Ireland in which case G. intactus would be a synonym of Bare-eyed Rail G. plumbeiventris, and even if the specimen is labelled correctly, it is probably only subspecifically distinct from G. plumbeiventris2.
References: 1. Knox and Walters (1994). 2. Taylor (1998).

Tricholimnas conditicius (Gilbert Rail) is known only from the type reputedly collected in the Apiang Group of the Gilbert Islands, Kiribati, in 18613. Walters4 asserted its specific status based on documentary evidence, but examination of the type (in Harvard) shows the form to be a synonym of Lord Howe Island Rail T. sylvestris1 3. 
References: 1. Greenway (1952). 2. Olson (1992). 3. Peters and Griscom (1928). 4. Walters (1987).

Calidris cooperi (Cooper's Sandpiper) was described by Baird in 1858 based on a specimen collected on Long Island, New York, U.S.A. in May 18332. There is a possible Australian record of a bird captured at Stockton, New South Wales, Australia, in Mar 19811, but studies of the type suggest that the form is of hybrid origin Curlew Sandpiper C. ferruginea x Sharp-tailed Sandpiper C. acuminata2. 
References: 1. Cox (1990a). 2. Cox (1990b).

Phalacrocorax kenyoni (Kenyon's Shag) is known only from 800-year-old midden bones and three skeletal specimens collected in the 1950s on Amchitka Island in the Aleutians, USA3. The taxon was considered Data-Deficient in 19941, but because it does not appear to be distinguishable from Pelagic Cormorant P. pelagicus2, it is now considered hypothetical only. 
References: 1. Collar et al. (1994). 2. Rohwer et al. (2000). 3. Siegel-Causey (1991).

Leguatia gigantea (Réunion Stork) is a much-disputed putative form based on historical descriptions of what were presumably Greater Flamingos Phoenicopterus ruber on Réunion (to France) 1; a single Ciconia bone from the island2 could indicate that this form was in fact a stork, but the weight of evidence suggests that the it represents either a natural, prehistoric, extinction, or, most likely, a bird killed and salted elsewhere and eventually eaten on Réunion1. 
References: 1. Cheke (1987). 2. Cowles (1987).

Sarcoramphus (papa) sacer was described by Bartram based on his records on the St. Johns River, Florida, in 1765-66 but is more likely referable to Crested Caracara C. plancus1. 
References: 1. AOU (1983).

Lalage leucopyga (Long-tailed Triller) was endemic to Norfolk Island, Australia3 from where it had become extinct by 19623. It may be a valid species1 but is usually treated as conspecific with the extant Long-billed Triller L. montrosieri2 4; the former name has priority and so if considered conspecific the species is named L. leucopyga2. 
References: 1. Christidis and Boles (1994). 2. Garnett (1993). 3. Knox and Walters (1994). 4. Stattersfield et al. (1998).

Rhipidura (fuliginosa) cervina (Lord Howe Fantail) was a common endemic to Lord Howe Island, Australia2. In 1918, Black rats Rattus rattus colonized the island from a shipwreck, causing the taxon to decline to rarity by 19241, and extinction by 19283. 
References: 1. Hindwood (1940). 2. Hull (1909). 3. Sharland (1929).

Turdus ulietensis (Bay Thrush) is known only from a description by Latham in 17891 and a painting by Forster (now in the British Museum), based on a specimen collected on 1 Jun 17742 both from Raiatea in the Society Islands, French Polynesia (to France)1. 
References: 1. Greenway (1967). 2. Knox and Walters (1994).

Necrospar legauti (Leguat's Starling) was described by Forbes in 1898 based on a single, albino specimen in Liverpool4, apparently from "Madagascar" and bought by Lord Derby from Verreaux in 18501. Forbes assumed without justification that it represented the birds described by Tafforet (see N. rodericanus) from the Ile du M‰t, Rodrigues (to Mauritius)1, and it has even been assumed to have come from Mauritius2 3, but its taxonomic and geographic origins remain obscure1. 
References: 1. Cheke (1987). 2. Hachisuka (1953). 3. Rothschild (1907). 4. Fisher (1981).

Foudia bruante (Réunion Fody) was described by Buffon in 1770-83 as endemic to Réunion (to France), but his plate appears to depict Madagascar Fody H. madascarensis, which is a common introduced species on Réunion1, and differs considerably from the birds described as abundant crop pests on the island by Dellon in 1668 and Dubois in 1671-721. This latter bird remains without a formal name1. 
References: 1. Cheke (1987).

Spiza townsendi (Townsend's Bunting) is the only one of Audubon's five "mystery birds" of which a specimen exists (in the Smithsonian); it is almost certainly a Dickissel S. americana lacking normal carotenoid pigments1. 
References: 1. Parkes (1987).

Possibly Extinct species
BirdLife applies a 'Possibly Extinct' tag to certain Critically Endangered species. The definition for this, and guidelines for its application, have been developed by examining information on c.50 species that have not been recorded for a long time or with dwindling populations that may have finally disappeared. The framework is currently being tested on other classes of taxa, but has not yet been officially incorporated into the IUCN Red List.

Species classified as Critically Endangered (Possibly Extinct) are defined by BirdLife as:

• Species that are likely to be extinct, but for which there is a small chance that they may still be extant, hence they should not be listed as EX until local or unconfirmed reports have been discounted, and adequate surveys have failed to find any individuals.

For each species, the following information is considered: (1) evidence pertaining to the timing of the last confirmed records; (2) any subsequent unconfirmed records or local reports; (3) knowledge about the strength of threatening processes currently and historically operating; (4) the adequacy of fieldwork relative to the (presumed) ease of detection of the species; and (5) the extent and quality of remaining suitable habitat (where 'suitable' incorporates the absence of introduced predators, pathogens etc).

Species are tagged as Possibly Extinct if, on balance, the evidence that they may be extinct outweighs any evidence that they may still be extant (although the latter remains a slim possibility, so they are not yet classified as Extinct).
Such evidence for extinction may include a combination of the following factors:

• There have been no confirmed records for a long time (it is difficult to be more prescriptive: the duration will depend on the intensity of fieldwork and the ease of detection).
• For species with recent last records, the decline has been well documented.
• There are severe threatening processes operating (e.g. extensive habitat loss, introduction of alien predators, intensive hunting).
• The species has attributes known to predispose it to extinction, e.g. it was probably naturally rare and/or had a tiny range (as evidenced by paucity of specimens relative to collecting effort), or flightless etc. In some cases, allospecies or congeners may have gone extinct through similar threatening processes.
• Surveys would have detected it (good/recent surveys have been adequate; species is unlikely to be overlooked).

Evidence that the species may remain extant may include a combination of the following factors:

• The lack of records is best explained by inadequate fieldwork (any surveys have been insufficiently intensive/extensive, or inappropriately timed; or the species's range is inaccessible, remote, unsafe or inadequately known)
• The lack of records is best explained by the fact that the species is difficult to detect (low density, cryptic, inconspicuous, nocturnal, nomadic, silent or call unknown, identification difficult)
• There have been reasonably convincing local reports or unconfirmed sightings
• Suitable habitat (free of introduced predators and pathogens if relevant) remains within the species's known range.
• In some cases, allospecies or congeners may survive despite similar threatening processes.