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Medium Tree-finch Camarhynchus pauper
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Justification
This species qualifies as Critically Endangered as it has a very small range on a single island, and recent information suggests that it is declining rapidly owing to the effects of the dipterid parasite Philornis downsi.

Taxonomic source(s)
SACC. 2006. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.html#.

Identification
12.5 cm. Chunky finch. Male has black head, greyish-brown upperparts, and whitish or yellowish underparts. Female has greyish-brown head. Similar spp. Differs from Large Tree-finch C. psittacula mainly in substantially smaller and less parrot-like bill, and from Small Tree-finch C. parvulus in larger bill. Voice Five-syllable series of tju notes or a dzi-dzi-dzi.

Distribution and population
Camarhynchus pauper is endemic to Floreana Island in the Galápagos Islands, Ecuador, where it has a small to moderate population in the highlands, and is uncommon to rare on the coast (Harris 1982,  H. Vargas and F. Cruz in litt. 2000, J. O'Connor in litt. 2010). Recent estimates put the total population at not more than 1,660 individuals, and it has recently begun declining rapidly owing to the effects of the introduced dipterid parasite Philornis downsi (O'Connor et al. 2010a, 2010b). Its largest population can be found around the base of the volcano Cerro Pajas, where its preferred nesting tree Scalesia pedunculata is dominant (O'Connor et al. 2010a).

Population justification
The maximum size of the population was estimated at 1,660 individuals in 2008. It is best placed in the band 1,000-2,499 individuals, equating to 667-1,666 mature individuals, rounded here to 600-1,700 mature individuals.

Trend justification
Numbers in 2008 were 39% of those recorded in 2004, indicating a decline outside the range expected for a fluctuating but stable population. Density fell from 154 birds/km2 in 2004 to 60 birds/km2 in 2008 at Cerro Pajas, and it is significantly less common now than it was 50 to 100 years ago (O'Connor et al. in prep.)

Ecology
It inhabits montane evergreen and tropical deciduous forest, and Scalesia-zone humid scrub (Stotz et al. 1996) mainly at elevations of 300-400 m (O'Connor et al. 2010a). It feeds on insects, nectar, young buds and leaves, probing crevices in the bark of trees and searching under twigs and foliage (Castro and Phillips 1996).

Threats
The most significant threat is from the introduced ectoparasite Philornis downsi, which occurs in finch nests on Floreana (Wiedenfeld et al. 2007), and is responsible for 41% of nestling mortality (O'Connor et al. 2010a, S. Kleindorfer in litt. 2008). In 2004-2008 nesting success was extremely low in all years (4-8 % of all nests producing fledglings), 28% of nestlings were predated, and parasite intensity from P. downsi was second highest of any bird species studied so far on the Galápagos archipelago (O'Connor et al. 2010a). It is thought to be at elevated risk from fly parasitism because its only extant habitat is adjacent to cleared agricultural land with fruiting trees which are favoured by the adult fly (S. Kleindorfer in litt. 2008). Floreana has a suite of introduced predators and herbivores including cattle, donkeys, pigs, cats, dogs and rats (Jackson 1985), and suffers from extensive habitat destruction and degradation as a result of agriculture (Cruz and Cruz 1996), habitat alteration by invasive plant species, and free-ranging domestic livestock (H. Vargas and F. Cruz in litt. 2000). Avian pox (Avipox virus) occurs on the island and infects a significant proportion of individuals. Predator marks from invasive rodents increased threefold between 2004-2008, and tourist visitation to favoured Scalesia habitat has increased more than tenfold since 2004 (S. Kleindorfer in litt. 2008). Having a montane distribution that is close to the maximum altitude within its range, this species is potentially susceptible to climate change (BirdLife International unpublished data).

Conservation Actions Underway
The Galápagos National Park was gazetted in 1959, and includes almost all the land area of the islands. Although the park incorporates most of Floreana, it does not include the agricultural zone of the island, an area which was the prime habitat for Medium Tree-finch. In 1979, the islands were declared a World Heritage Site (Jackson 1985). In December 2006, the Galápagos National Park began the eradication of goats and donkeys on Floreana which successful reduced their population to negligible numbers (J. O'Connor in litt. 2010). The Galápagos National Park places rat baiting stations around the Critically Endangered Galápagos Petrel breeding colony in the centre of Cerro Pajas, which may also reduce nest predation of Medium Tree-Finches in the immediate area (J. O'Connor in litt. 2010). Methods to control or eradicate Philornis downsi are currently being trialled by researchers and visiting scientists at the Charles Darwin Research Station (J. O'Connor in litt. 2010). Conservation Actions Proposed
Investigate methods to control or eradicate Philornis downsi. Continue to monitor the population size. Extend the national park to incorporate the agricultural zone on Floreana. Continue and extend control measures against introduced species.

References
Castro, I.; Phillips, A. 1996. A guide to the birds of the Galápagos Islands. A&C Black, London.

Christensen, R.; Kleindorfer, S. 2009. Jack of all trades or master of one? Variation in foraging specialisation across years in Darwin's Tree Finches (Camarhynchus spp.). Journal of Ornithology 150(2): 383-391.

Cruz, J. B.; Cruz, F. 1996. Conservation of the Dark-rumped Petrel Pterodroma phaeopygia of the Galápagos Islands, 1982-1991. Bird Conservation International 6: 23-32.

Grant, P. R.; Grant, B. R.; Petren, K.; Keller, L. F. 2005. Extinction behind our backs: the possible fate of one of the Darwin’s finch species on Isla Floreana, Galápagos. Biological Conservation 122: 499-503.

Harris, M. P. 1982. A field guide to the birds of Galápagos. Collins, London.

Jackson, M. H. 1985. Galapagos: a natural history guide. Calgary University Press, Calgary, Canada.

O'Connor, J.A., Sulloway, F.J. and Kleindorfer, S. 2010. Avian population survey in the Floreana highlands: is Darwin's medium tree finch declining in remnant patches of Scalesia forest? Bird Conservation International 20(4): 343-353.

O'Connor, J.A., Sulloway, F.J., Robertson, J. and Kleindorfer, S. 2010. Philornis downsi parasitism is the primary cause of nestling mortality in the critically endangered Darwin's medium tree finch (Camarhynchus pauper). Biodiversity and Conservation 19(3): 853-866.

O’Connor, J. A.; Sulloway, F. J.; Kleindorfer, S. in press. Avian population survey in the Floreana highlands: Is Darwin’s medium tree finch declining in remnant patches of Scalesia forest? Bird Conservation International.

Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

Wiedenfeld, D. A.; Jiménez, G. A.; Fessl, B.; Kleindorfer, S.; Valerezo, J. C. 2007. Distribution of the introduced parasitic fly Philornis downsi (Diptera, Muscidae) in the Galapagos Islands. Pacific Conservation Biology 13: 14-19.

Further web sources of information
Alliance for Zero Extinction (AZE) species/site profile. This species has been identified as an AZE trigger due to its IUCN Red List status and limited range.

Click here for more information about the Alliance for Zero Extinction (AZE)

Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Isherwood, I., McClellan, R., Pople, R., Sharpe, C J, Symes, A., Khwaja, N.

Contributors
Cruz, F., Kleindorfer, S., O'Connor, J., Vargas, H., Wiedenfeld, D.

Recommended citation
BirdLife International (2014) Species factsheet: Camarhynchus pauper. Downloaded from http://www.birdlife.org on 22/12/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/12/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Medium tree-finch (Camarhynchus pauper) 0

Key facts
Current IUCN Red List category Critically Endangered
Family Emberizidae (Buntings, American sparrows and allies)
Species name author Ridgway, 1890
Population size 600-1700 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 23 km2
Country endemic? Yes
Links to further information
- Additional Information on this species