Justification of Red List Category
The majority of the population of this species occurs on the island of Saipan, where the Brown Tree Snake (Boiga irregularis) may possibly be in the process of becoming established. This would lead to an extremely rapid population reduction in the near future and the species is precautionarily classified as Critically Endangered. Fortunately, there has been little evidence of Brown Tree Snakes colonising any islands outside of Guam, and this species might be down-listed after a more detailed assessment of this threat.
The species occurs on Saipan (71,997 individuals) and Aguiguan (15,499 individuals) (Camp et al. 2009, Amidon et al. 2014), equating to a global population of c. 87,000 individuals. A third population was established on the uninhabited island of Sarigan through translocations of 24 and 50 individuals in 2011 and 2012, respectively (Radley 2012).
An extremely rapid population decline, which may well have already begun, is projected over the next ten years owing to the possible establishment of the Brown Tree Snake (Boiga irregularis) on Saipan.
Cleptornis marchei is endemic to the Northern Mariana Islands (to USA), occurring on Saipan (115 km2) where, in 2007, the population was estimated at 71,997 (47,586–106,535 95% C.I.) individuals (Camp et al. 2009), and on the uninhabited Aguiguan (7 km2), where the population was estimated at 15,499 (10,383-22,277 95% C.I.) birds (Amidon et al. 2014). The species is now also found on Sarigan after translocations of individuals from Saipan took place (Radley 2012).
The density estimate for the Golden White-eye on Aguiguan in 2008 was three times greater than for Saipan in 2007 (Amidon et al. 2014), and indeed densities on Aguiguan were significantly greater in 2008 (24.33 birds/ha, 16.30-34.97 95% C.I.) than in 1982 (10.94 birds/ha, 7.53-15.08 95% C.I., Amidon et al. 2014). Population densities (birds per km2 ±SE) on Saipan have been shown to have declined from 1,287.2 ± 191.0 in 1982 to 995.5±160.0 in 1997 and to 711.8±112.1 in 2007 (Camp et al. 2009), although data from roadside surveys on Saipan appears to show that the species may have increased during the 1990s, and then declined in the 2000s (Ha et al. 2018).
On Saipan, the Golden White-eye occurs in all wooded habitats, including the native limestone forest (which is restricted to steep slopes and cliffs and covers c. 5% of the island), and introduced tangan tangan (Leucaena leucocephala) thickets on flat lowlands and plateaus (c. 28% of land cover), and also urban areas (Pratt et al. 1987, Craig 1990, A. Tieber in litt. 2008, 2010). However, it is decidedly more common in limestone forest than in disturbed areas (Craig 1996), and higher nesting densities are recorded in limestone forest than tangan tangan thickets (Sachtleben 2005). It forages predominantly in the foliage of trees, particularly Cynometra ramifolia, feeding on invertebrates, flying insects, nectar, fruit and flowers and also taking insects from tree bark (Pratt et al. 1987, Craig 1990) and is typically seen in small groups of 2-4 individuals, thought to be family groups (A. Tieber in litt. 2008, 2010). Mean clutch size is 1.85 eggs (n = 39) (Peiffer 2014). Nest predators include the native Mariana Kingfisher, and the introduced Emerald Tree Skink and rats Rattus spp. (Peiffer 2014).
The species's ability to utilise different habitats may help to explain its persistence despite periodic typhoon damage and extensive, human-caused habitat change (Craig 1990). The potential establishment of Brown Tree Snake (Boiga irregularis) on Saipan poses a major threat to the population (Rodda and Savidge 2007) and would likely lead to extremely rapid declines, as has been the case amongst the endemic avifauna of Guam (to USA) (A. Saunders in litt. 2003, Wiles et al. 2003, Williams 2004), but there are no data as yet on predation of the Golden White-eye (A. Tieber in litt. 2008, 2010). Aguiguan is uninhabited and difficult to access and it is unlikely that snakes will be accidentally introduced there (J. Lepson in litt. 1999) - as of 2008 there had been no reports of snakes on the island (A. Tieber in litt. 2008, 2010). Having a distribution on relatively low-lying islands, this species is potentially susceptible to climate change through sea-level rise and increased typhoon frequency and/or intensity (BirdLife International unpublished data). It may also be impacted by a shift in suitable climatic conditions; both wet and dry seasons are predicted to be wetter and warmer in the western Pacific, including the Marianas. Saracco et al. (2016) suggest that such conditions could have negative consequences for the Golden White-eye, which appears to exhibit higher reproductive output in years with a relative contrast in greenness (P. Radley in litt. 2016). The Golden White-eye is regarded as a Species of Greatest Conservation Need by the CNMI Division of Fish and Wildlife, due to threats from commercial and residential development, feral ungulates, invasive vines, and the potential for establishment of the Brown Tree Snake (Liske-Clark, 2015).
Conservation and Research Actions Underway
Although not directed solely at the conservation of this species, extensive efforts are underway to determine the status of Brown Tree Snake (Boiga irregularis) on Saipan and, should an established population be identified, to control it immediately (N. Hawley in litt. 2007). Efforts are also underway to develop captive breeding techniques for the species. The MAC Project brought 24 Golden White-eyes into captivity in 2007 and another 24 in 2008, with successful breeding reported from four institutions (MAC Working Group 2013). As of 31 December 2015, there is a living captive population of 49 Golden White-eyes, comprised of 25 males and 24 females, across 10 institutions in the U.S. All institutions have developed captive breeding protocols but chick mortality is one of the largest problems among all holders. There were 12 hatches in 2015, none of which survived. In April 2011, 24 Golden White-eyes were captured on Saipan and translocated to Sarigan (Radley 2012). A second cohort of 50 Golden White-eyes were captured on Saipan and released on Sarigan in May 2012 (Radley 2012). A research project known as Tropical Monitoring of Avian Productivity and Survivorship (TMAPS) is ongoing (P. Radley in litt. 2016). Its intent is to investigate the seasonal components of demographic rates of Golden White-eyes and other species on Saipan, and how these vital rates relate to temporal variations in local habitat quality (Saracco et al. 2016). Observations of unbanded birds were made on Sarigan in 2015 and 2016, indicating the species had successfully bred (L. Zarones in litt. 2016). Conservation and Research Actions Proposed
Monitor population trends through detailed censuses (G. Wiles in litt. 1999). Continue to control the Boiga irregularis population by trapping at ports and monitoring its spread. Develop and implement techniques to control small incipient populations of B. irregularis (F. Amidon in litt. 2007). Continue to develop techniques for establishing a captive population and establish new wild populations, as appropriate (F. Amidon in litt. 2007, Liske-Clark 2015). Continue to monitor the translocated population on Sarigan. Future translocations are planned to establish a population on the island of Alamagan (MAC Working Group 2013, P. Radley in litt. 2016).
14 cm. Medium-sized, bright, warbler-like bird. Golden-yellow or peach-coloured, browner above, with bright orange bill, legs, and feet. Yellowish-white eye-ring. Voice Flock calls a rasping schik and a loud whistle. Song a rolling warble SEE-ME-can-you-SEE-ME-I-can-SEE-YOU-can-you-SEE-ME ...
Text account compilers
Shutes, S., Stattersfield, A., North, A., Symes, A., Benstead, P., Wright, L, Derhé, M., Mahood, S., Westrip, J., Bird, J., O'Brien, A.
Amidon, F.A., Hawley, N., Lepson, J., Saunders, A., Tieber, A., Wiles, G., Radley, P. & Zarones, L.
BirdLife International (2020) Species factsheet: Cleptornis marchei. Downloaded from http://www.birdlife.org on 26/11/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/11/2020.