As of December 2020, the International Union for Conservation of Nature (IUCN) lists 46 data deficient avian species.^[1] 0.47% of all evaluated avian species are listed as data deficient. No subpopulations of birds have been evaluated by the IUCN.

•   Extinct in the wild (EW): 5 species
•   Critically endangered (CR): 223 species
•   Endangered (EN): 460 species
•   Vulnerable (VU): 798 species
•   Near threatened (NT): 1,001 species
•   Least concern (LC): 8,460 species
•   Data deficient (DD): 46 species

Avian species (IUCN, 2020-3)

• 10,999 extant species have been evaluated
• 10,947 of those are fully assessed^[a]
• 9,461 are not threatened at present^[b]
• 1,481 to 1,533 are threatened^[c]
• 164 to 183 are extinct or extinct in the wild:
  • 159 extinct (EX) species^[d]
  • 5 extinct in the wild (EW)
  • 19 possibly extinct [CR(PE)]

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1. ^ excludes data deficient evaluations.
2. ^ NT and LC.
3. ^ Threatened comprises CR, EN and VU. Upper estimate additionally includes DD.
4. ^ Chart omits extinct (EX) species

This is a complete list of data deficient avian species evaluated by the IUCN. Where possible common names for taxa are given while links point to the scientific name used by the IUCN.