The Maui Parrotbill is an endangered Hawaiian honeycreeper that was first collected in 1892 by Henry Palmer and described by Rothschild ( Rothschild, L. W. 1893a. Avifauna of Laysan and the neighboring islands with a complete history to date of the birds of the Hawaiian possessions, Pt. III. London, U.K: R. H. Porter. Close Rothschild 1893a). No Hawaiian name for the species survives. Currently restricted to the remote high-elevation rain forests of eastern Maui, the Maui Parrotbill was thought to be extinct until its rediscovery in 1950 ( Richards, L. P. and P. H. Baldwin. 1953. Recent records of some Hawaiian honeycreepers. Condor no. 55:221-222. Close Richards and Baldwin 1953). Today the population is estimated to be about 500 birds ( Scott, J. M., S. Mountainspring, F. L. Ramsaey and C. B. Kepler. 1986. Forest bird communities of the Hawaiian Islands: their dynamics, ecology, and conservation. Stud. Avian Biol. no. no. 9. Close Scott et al. 1986).

Before the 1980s, various naturalists had encountered Maui Parrotbill but had collected little detailed information ( Wilson, S. B. and A. H. Evans. 1890. Aves Hawaiienses: the birds of the Sandwich Islands. London: R. H. Porter. Close Wilson and Evans 1890, Rothschild, L. W. 1893a. Avifauna of Laysan and the neighboring islands with a complete history to date of the birds of the Hawaiian possessions, Pt. III. London, U.K: R. H. Porter. Close Rothschild 1893a, Henshaw, H. W. 1902a. Birds of the Hawaiian Islands being a complete list of the birds of the Hawaiian possessions with notes on their habits. Honolulu, HI: Thomas G. Thrum. Close Henshaw 1902a, Perkins, R. C. L. 1903. Fauna Hawaiiensis, Vol. I, pt. IV: Vertebrata. Edited by D. Sharp. England: Cambridge Univ. Press. Close Perkins 1903, Banko, W. E. 1968. Rediscovery of Maui Nukupu'u, Hemignathus lucidus affinis, and sighting of Maui Parrotbill, Pseudonestor xanthophrys, at Kipahulu Valley, Maui, Hawai'i. Condor no. 70:265-266. Close Banko 1968, Scott, J. M. and J. L. Sincock. 1977. Recent observations on the birds of the Koolau Forest Reserve, Maui. West. Birds no. 8:113-116. Close Scott and Sincock 1977). Very little was known about the species until biologists began natural history studies in the 1980s, and the first confirmed active nest was not discovered until 1993 ( Van Gelder, E. 1993. First Maui Parrotbill nests found. Hawai'i's Forests and Wildlife no. 8 (1):9. Close Van Gelder 1993, Lockwood, J. L., J. E. Green, K. Wakelee, E. Van Gelder, S. Ashe and R. Aburomia. 1994. A description of Maui Parrotbill (Pseudonestor xanthophrys) nests and nesting behavior. 'Elepaio no. 54 (10):61-64. Close Lockwood et al. 1994).

The Maui Parrotbill is a small, olive-green bird with a relatively large, parrotlike bill, which it uses to rip into branches and stems, to pluck and bite open fruit, and to lift bark and lichens in search of concealed invertebrates. It is one of the most sexually dimorphic of Hawaiian honeycreepers: Males are much larger than females, and their underparts are brighter yellow. Chicks are fed by regurgitation, and because fledglings remain dependent on their parents for 5 months or longer, sightings are frequently of family groups.

The ecology of this species remains poorly known, but ongoing research should provide much needed information, especially about factors affecting productivity. Such understanding will be essential in developing management strategies to help safeguard the future of the Maui Parrotbill.