Justification of Red List Category
This species qualifies as Endangered because it is restricted to four very small islands, including Saipan, where brown tree snake Boiga irregularis may be in the process of becoming established, and Tinian and Rota where the snake has also been detected. These three islands support 97% of the population. It formerly occurred on Guam, where it was extirpated by brown tree-snake. It is therefore very likely to undergo a rapid overall population decline in the immediate future. 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.
Based on the most recent surveys, the population was estimated at 16,230 birds, consisting of 9,723 on Saipan (data from 2007 [Camp et al. 2009]), 2,269 on Tinian (data from 2008, [Camp et al. 2012]), 3,383 on Rota (data from 2012 [Camp et al. 2015]) and 855 on Aguijan (data from 2008 [Amidon et al. 2014]).
Analysis of survey data from 1982, 1997 and 2007 indicates that the species' population appears stable on Saipan between 1982 and 2007 (Camp et al. 2009). Surveys in 2008 on Aguijan indicate that the population increased from estimates in 1982 (Amidon et al. in prep.). Surveys in 2008 on Tinian (Camp et al. in press) and 2003 on Rota (Amar et al. 2008) indicate a significant decline on those islands since 1982 . The species has been recently reported on the island of Sarigan, one of the volcanic islands north of Saipan, and may become established on the island through natural colonization. The future rate of decline may be very rapid on Saipan, owing to predation by B. irregularis.
Ptilinopus roseicapilla is fairly common on four islands in the Northern Mariana Islands (to USA), where it is primarily a bird of mature forest although it is also found in some moderately disturbed mixed woodland and second growth habitats (Engbring et al. 1982, Jenkins 1983, Craig 1996, Camp et al. 2009. 2012, 2015, Amidon et al. 2014). It has become extirpated from Guam (to USA) owing to predation by the introduced brown tree snake Boiga irregularis, and although single birds turn up once every few years, these are almost certainly individuals dispersing from the island of Rota, 60 km to the north (G. Wiles in litt. 1999). In 1982, the total population was estimated at 9,443 birds, with 2,541 on Saipan, 3,075 on Tinian, 3,535 on Rota and 292 on Aguijan (Engbring et al. 1982). Surveys conducted over the last decade indicate that the species appears stable on Aguijan (data from 2008 [Amidon et al. 2014]), and Saipan (data from 2007 [Camp et al. 2009]), and declined on Rota (data from 2012 [Camp et al. 2015]) and Tinian (data from 2008, [Camp et al. 2012]). A recent Promoting Protection through Pride campaign on Rota has resulted in legislation fully protecting the species from hunting and trapping (T. Holm in litt. 2000). However, the species must be affected by habitat loss and is at great risk from the recent introduction of B. irregularis to Saipan, and the likely introduction to Tinian and Rota.
This species eats a variety of fruit from the forest canopy (Engbring et al. 1982) particularly from native Ficus spp. and Premna obtusifolia trees. It may also descend to feed in bushes or on the ground, where it takes the fruits of the introduced prostrate vine Momordica charantia (del Hoyo et al. 1997). It is found in a variety of forest types but appears more common in limestone forest (Craig 1996) and to prefer mature native forest (del Hoyo et al. 1997). On Aguijan it is found in heavily grazed forest and on Tinian in the scrubland of introduced Leucaena trees. It seems to breed all year round with a peak in breeding activity and consequently population size during April-July (Craig 1996). It lays one egg in a nest approximately 2.8 m from the ground (del Hoyo et al. 1997).
Persistent reports from the island of Saipan suggest that the brown tree snake may be in the process of becoming established on the island (Rodd and Savidge 2007), and has also been detected on Tinian and Rota (A. Saunders in litt. 2003, Williams 2004). Although it appears to not yet be established on Tinian and Rota (Amindon in litt. 2007), there is a risk it may be in the future since tourism development and military buildup on Tinian necessitates the importation of large amounts of building materials (J. Lepson in litt. 1999). Unless the snake can be controlled on Guam and Saipan and prevented from becoming established on Tinian and Rota, the populations on three islands are likely to be extirpated rapidly. Other threats include the spread of introduced plant species, especially Leucaena, habitat destruction and hunting (del Hoyo et al. 1997).
Conservation Actions Underway
A recent Promoting Protection through Pride campaign on Rota has resulted in legislation fully protecting the species from hunting and trapping (T. Holm in litt. 2000). A brown tree-snake barrier was constructed at the port on Tinian and plans are underway to build a barrier at the port on Rota to support interdiction efforts (Amindon in litt. 2007, Hawley in litt. 2007). The Mariana fruit dove captive breeding program began in 1993 under the umbrella of the Mariana Archipelago Rescue & Survey (MARS) program and has now evolved into Mariana Avifauna Conservation Program (MAC) (H. Roberts in litt. 2009).
24 cm. Small, mostly green fruit-dove. Rose-red forehead, with the remainder of the head, neck, back and breast being silvery-grey, remaining upperparts green. Underparts mostly green with purple patch in lower breast, and yellow belly patch and undertail coverts. Voice Undescribed.
Text account compilers
Benstead, P., Derhé, M., Mahood, S., O'Brien, A., Shutes, S. & Stattersfield, A.
Amidon, F., Hawley, N., Roberts, H., Saunders, A., Holmes, T., Lepson, J., Wiles, G. & Camp, R.
BirdLife International (2020) Species factsheet: Ptilinopus roseicapilla. Downloaded from http://www.birdlife.org on 09/07/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/07/2020.