Justification of Red List Category
This species has been uplisted to Vulnerable. The species has declined significantly on the island of Santa Cruz and is likely to also be declining on other islands within its range, owing to habitat loss and degradation.
The global population size has not been quantified, but this species is described as 'uncommon' in at least parts of its range (Stotz et al. 1996). On the island of Santa Cruz its population has been estimated at 9,000 singing males (Dvorak et al. 2012). However no data exists for the islands of Isabela and Santiago.
The population is suspected to be decreasing rapidly. On the island of Santa Cruz, the species reportedly declined significantly in the dry zone between 1997 and 2010, but not in the Scalesia zone (Dvorak et al. 2012). Habitat alteration, introduced pathogens and parasites and changes in insect availability may have contributed to declines. On the islands of Isabela and Santiago, where native forest has also been degraded (by introduced herbivores) population declines are also suspected (Dvorak et al. 2012).
This species is endemic to the Galápagos islands, (Ecuador), with breeding populations on Isabela, Santa Cruz, Santa Fé, Fernandina, Santiago, Marchena, Pinta and Rábida (Castro and Phillips 1996, Stotz et al. 1996). It is extinct on Pinzón (Castro and Phillips 1996) and thought to be extinct on Floreana (Kleindorfer et al. 2014, Jaramillo and Sharpe 2015).
This species inhabits lowland deciduous and montane evergreen forest, between 300 and 700 m altitude (Stotz et al. 1996). On Santa Cruz in the dry zone it is restricted to areas with tall palo santo Bursera graveolens trees, it is also found in the Scalesia zone and locally in the agricultural zone (Dvorak et al. 2012). It feeds on the fruits of native plant species, and on insects for which it forages under leaves and excavates dead branches (Castro and Phillips 1996). It may move to lower elevations during the dry season (Jaramillo and Sharpe 2015).
The species is likely to be affected by a number of threats. Development, introduced herbivores, the spread of invasive alien plant species and the herbicides used to manage these invasions may all have contributed to unfavourable habitat conditions for the species on Santa Cruz (Dvorak et al. 2012). The introduced parasitic fly Philornis downsi is known to have a negative impact on nesting success in Galápagos finches and the species may be susceptible to avian pox. Severe weather and changes in rainfall patterns owing to climate change also pose a threat.
Conservation and Research Actions Underway
No actions are currently known.
Conservation and Research Actions Proposed
Implement a full-scale monitoring programme across the Galápagos Islands. Ensure that management activities to control invasive alien plant species do not have a negative impact on Large Tree-finch. Investigate drivers behind observed declines and assess the impact of Philornis downsi on the population. Protect and enhance existing habitat.
13 cm, largest tree-finch. Deep bill, approximately as long as it is deep. Mandible tips cross slightly when bill closed. Male has upperparts greyish-olive and whitish below, with blackish hood. Female is dull greyish brown (Jaramillo and Sharpe 2015). Voice Song a repeated series of 4-6 notes given in pairs chu-tzee chu-tzee chut-zee. Call includes a nasal tzeeuu.
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J., Fisher, S., Harding, M., Sharpe, C J
BirdLife International (2021) Species factsheet: Geospiza psittacula. Downloaded from http://www.birdlife.org on 09/03/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/03/2021.