Justification of Red List Category
This forest species qualifies as Endangered because it has a very small population and a small, fragmented range that is declining as the quality of its forest habitat diminishes.
It was found to be common but patchily distributed in Savaii highland forests in 2005 (Pratt and Mittermeier 2016). The Rapid Biodiversity Assessment of Upland Savaii, Samoa, conducted in 2012 detected small numbers at two sites on the island (Atherton and Jefferies 2012, p. 14). The ICCRIF study of 2014 found it in only one of five sites it surveyed (R. Stirnemann in litt. 2016). This is consistent with a precautionary estimate of a population size of c.500 individuals (F.T. Tipanaa in litt. 2007), and it is placed here in the band 250-999 mature individuals. This equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.
The species is suspected to be undergoing a moderate decline owing to habitat degradation and predation by introduced mammals, which is on-going.
Gymnomyza samoensis occurs on Savai`i and `Upolu, Samoa, and may have occurred formerly on Tutuila, American Samoa (it was collected there in the 1920's). In 1984, it was common in preferred habitat on `Upolu (Bellingham and Davis 1988) but it appears to have become rarer. For example, it was not recorded by two main-island surveys (Lovegrove et al. 1992, Park et al. 1992) nor by offshore island surveys in 1999 (Freifeld et al. in press), and only one individual was recorded at the proposed conservation area at Uafato in 1997 (Beichle 1997b). It was found to be common but patchily distributed in Savaii highland forests in 2005 (Pratt and Mittermeier 2016). The Rapid Biodiversity Assessment of Upland Savaii, Samoa, conducted in 2012 detected small numbers at two sites on the island (Atherton and Jefferies 2012, p. 14). While the ICCRIF study of 2014 found it in only one of five sites it surveyed (R. Stirnemann in litt. 2016). The population size is thought to be little more than 500 individuals (F.T. Tipamaa in litt. 2007).
This large honeyeater occurs in foothill and montane forest. It has also been observed in an area of cinder cone, heathland scrub, at forest edge, in the wet forest at 760 m (Reed 1980) and on steep slopes along rivers (Stirnemann in litt. 2016). It has been observed feeding on a wide range of flowers trees including the flowers of the coral trees Erythrina spp., mistletoe, heliconia, ginger, banana and some orchids species (R. Stirnemann in litt. 2012). Insects are also an important part of the diet and are the main food source in the dry season. During breeding, a simple nest is constructed in a tree, at varying heights above 5m, and a single egg is laid (Stirnemann et al. 2015). In the nest, the chick is fed a mix of invertebrates and geckos. Incubation lasts 19 days, and chicks fledge 21-22 days after hatching (Stirneman et al. 2015). Juveniles are dependent on adults for approximately 8 to 10 weeks post-fledging (Stirnemann et al. 2015). The female is almost exclusively responsible for incubation and feeding the chick, and both adults defend the nest. Pairs are highly territorial with high site fidelity (Stirnemann et al. 2015).
Forest clearance is an ongoing threat to the species (MNRE 2006). In surveys in upland Savai'i, it was not recorded in the disturbed forests above Asau and were only found on a limited altitudinal range on the A’opo trail (Atherton and Jefferies 2012). Slash-and-burn cultivation threatens remaining areas of upland forest, as farmers use forestry roads from heavily logged lowland forests to gain access to formerly inaccessible land (Bellingham and Davis 1988). The species is also likely to have suffered following cyclones Ofa and Val in 1990 and 1991, when canopy cover was reduced from 100% to 27% (Elmqvist et al. 1994). Habitat quality was degraded with the loss of closed-canopy forest increasing the emergence of invasive and weedy species (MNRE 2006, Butler and Stirnemann 2013). Forest quality has also declined because of the invasion of highly aggressive non-native trees, whose spread is aided by hurricanes (H. Freifeld in litt. 1999). Although it forages and occasionally nests in modified habitat such as plantations, these increase predation risk by non-native predators such as rats (Stirneman et al. 2015b). Predation by both introduced rats Rattus sp. and cats is likely to be having a significant impact on the species (Stirnemann in litt. 2012). Nest predation by black rats Rattus rattus was observed twice. In both cases the rat jumped onto an incubating female, driving her off the nest. During the same study two adult females also dissapeared during the breeding season. Footage suggests that incubating adult females are potentially vulnerable to predation on the nest (Stirnemann et al. 2015b). This could bias predation risk towards adult females. As a result, a skewed sex ratio may form (Stirnemann et al. 2015b). The behaviour of juveniles also places them at risk of predation. In the week post-fledging they spend a considerable time on the forest floor where they are at risk from predation by feral cats (Stirnemann et al. 2015b)
Conservation Actions Underway
A species recovery plan has been published (MNRE 2006). The species occurs in some proposed and a few existing protected areas, but these have suffered cyclone damage and the O Le Pupu Pu`e National Park on `Upolu is threatened by logging and cattle-farming (Beichle and Maelzer 1985, Bellingham and Davis 1988). Field surveys were carried out in 2015 and 2016 have been identifying some priority areas for the species (Stirnemann in litt. 2016), though a full survey across the entire country isolating key habitat areas has not yet occurred. Research was carried out looking at reproductive success and the effect of habitat modification on nest predation (2010-2013) (Stirnemann et al. 2015, 2015b). Studies indicate that rat predation is higher in areas with plantations present, but nest predation is occurring across the landscape.
Conservation Actions Proposed
The Government of Samoa developed a recovery plan in 2006. The recovery plan identifies goals of securing the species, maintaining its existing populations on 'Upolu and Savai'i, and re-establishing populations at former sites. Some of these goals have now been met. However, there is still information lacking on its distribution, current population size and it’s life-history and habitat requirements (Stirnemann et al. 2015). Research has highlighted the need to respond to identified threats such as rats and cats in some key areas to increase breeding success and reduce adult female mortality on the nest (Stirnemann et al. 2015b). Identification of important sites for forest restoration and their increased protection is also required, especially since logging of primary forest still continues in Samoa. It is also necessary to establish a network of long-term monitoring stations so population changes can be monitored. Given that 80% of land in Samoa is communally owned it is critical that there is increase local involvement and education on the species and conservation in general. The problem of introduced plants such as the invasive rubber tree also needs to be addressed. Rubber plants are taking over the forest and resulting in 'empty bird forests' particularly in 'Upolu (H. Freifeld in litt. 1999, Stirnemann pers com. 2016). Survey suitable habitat on Tutuila, American Samoa, to investigate if its re-establishment is feasible.
31 cm. Large, dark honeyeater with long, slightly decurved bill. Sooty-black head, shading to dusky olive-green posteriorly and on wings, slightly tawny on undertail-coverts. Olive streak under eye. Eyes are blue in adults and brown in chicks. Similar spp. Samoan Starling Aplonis atrifusca has heavier, less pointed and curved bill, is brownish-black with no green tones. Voice Calls include mechanical-sounding chips and short squeaks. Song a composite of cat-like squeaky wails and cries and hoarse low notes.
Text account compilers
Derhé, M., Dutson, G., Mahood, S., O'Brien, A., Shutes, S., Stattersfield, A.
Stirnemann, R., Freifeld, H., Tipamaa, F., Beichle, U.
BirdLife International (2020) Species factsheet: Gymnomyza samoensis. Downloaded from http://www.birdlife.org on 14/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/08/2020.