Data Zone
Justification of Red List category
This species has a very small area of occupancy and its habitat is declining in extent and quality as a result of sea level rise due to climate change, forest degradation caused by feral ungulates, and forest clearance for residential and commercial development. Island subpopulations are at risk from stochastic events such as typhoons and volcanic eruptions, as well as further introductions of invasive species such as the Brown Tree Snake. The number of locations is therefore likely to be small, but larger than ten. For these reasons, the species is listed as Near Threatened.
Population justification
In Palau, the species is widely-distributed, but generally uncommon to rare, and only locally distributed (VanderWerf and Dittmar 2020). Surveys throughout the archipelago (excluding Kayangel Atoll) in 1991 led to population estimates of 244 (+/- 173) individuals on Babeldaob, 104 (+/- 34) in the Rock Islands (excluding Ngerukeuid), 52 (+/- 41) on Peleliu, and 97 (+/- 43) on Angaur, with a total population estimate of 497 (+/- 291) individuals (Engbring 1992, VanderWerf and Dittmar 2020). This may equate to approximately 330 (137-525) mature individuals. Recent surveys have estimated the Kayangel Atoll population to be 108 mature individuals (Olsen et al. 2016), so the total Palau population in 1991 may have been c. 438 (245-633) mature individuals.
Repeat surveys in 2005 produced population estimates of 301 (+/- 171) individuals on Babeldaob, 227 (+/- 133) in the Rock Islands, 48 (+/- 32) on Peleliu, and 125 (+/- 71) on Angaur, leading to an estimated total population in Palau (excluding Kayangel Atoll) of 700 (+/- 308) individuals (VanderWerf 2007, VanderWerf and Dittmar 2020). This may equate to approximately 466 (261-672) mature individuals. The population estimates for Peleliu and the Rock Islands may have been underestimated because areas known to be used for nest-building were not surveyed (VanderWerf and Dittmar 2020). Recent surveys have estimated the Kayangel Atoll population to be 108 mature individuals (Olsen et al. 2016), so the total Palau population in 2005 may have been c. 574 (369-780) mature individuals.
A survey of nesting mounds across 122 beaches across Palau (excluding Angaur) in 2011-2013 recorded 173 active nesting mounds distributed across 53 sites, indicated a population of c.346 mature individuals (Olsen et al. 2016). 95 (55%) of the recorded active nesting mounds were in the Rock Islands, 54 (31%; 108 mature individuals) were in Kayangel Atoll (including three on Ngeriungs Islet and one on Ngerbelas Islet), 13 (8%) were on coastal islets of Babeldaob, and the remaining 11 (6%) were on Peleliu and nearby islets (Olsen et al. 2016). Assuming that the 125 individuals estimated for Anguar in 1992 may equate to roughly 83 mature individuals, the total population in Palau in 2013 may have been approximately 429 mature individuals.
Playback surveys in the Rock Islands in 2017 found higher densities, suggesting that previous surveys may have underestimated the population size in Palau (P. Radley in litt. 2020). These surveys also suggested that the number of nesting sites may have declined by 5-10% since 2013 (Radley 2019). Since previous surveys indicated a population reduction in the Rock Islands but no overall decline for Palau (VanderWerf 2007, VanderWerf and Dittmar 2020), the population in Palau is assumed not to have changed significantly since 2013.
Taking into account the above population estimates, the total population in Palau is placed in the band 245-780 mature individuals, with a best estimate of 420-580 mature individuals (based on the best estimates from the surveys in 2005 and 2011-2013).
In 1998, the total population in the Marianas was estimated to number 1,440 to 1,975 birds (USFWS 1998). Extensive surveys in 2010 combined with DISTANCE analysis resulted in much higher estimates than previously reported, with a total estimated population in the northern islands (Saipan, Sarigan, Guguan, Alamagan, Pagan, Agrihan, Asuncion, and Maug; excluding Aguiguan, Farallon de Medinilla, Anatahan and Tinian) of 10,727 individuals (95% CI: 6,682—15,445), with the majority of the population found on the islands of Asuncion, Sarigan and Guguan (Amidon et al. 2011). The higher estimate was believed to be largely due to increased survey effort, including the use of playback surveys, but may also have reflected the removal of ungulates from Sarigan in 1998 (Amidon et al. 2011). The use of pooled analysis from data across islands together with assumptions about habitat occupancy may have led to this estimate being too high (P. Radley in litt. 2021).
On Aguiguan, surveys in 2000 and 2002 estimated a population size over 0.5 km2 of forest at 80 (43-149) and 72 (34-149) individuals, respectively (Esselstyn et al. 2003). Subsequent research using playback indicated a territory size of 3.76 ha in limestone forest on the island, indicating a population size of 112 individuals (61–206; 95% CI; Kessler and Amidon 2009, Amidon et al. 2011).
On Tinian, surveys in 1982 and 1994 did not detect any individuals (Engbring et al.1986, USFWS 1998), but incidental reports from the 1990s suggested that a very small population (<10 individuals) may persist (O'Daniel and Krueger 1999, USFWS 1998). None were detected during surveys in 2008 (Camp et al. 2012a,b).
Surveys on Saipan in 1982 lead to a population estimate of 40 individuals (Engbring et al. 1986). Repeat surveys in 1991-1992 lead to an estimated population size of 14 birds in the native forests of the Marpi region (Craig et al. 1993, Craig 1996). No individuals were recorded during surveys in other parts of the island where the species was previously recorded, leading to the conclusion that the population on Saipan was declining (Craig 1996). In 1997, the population on Saipan was thought likely to be less than 30 individuals (USFWS 1998). Following surveys in 2010 and analysis using a modelled detection function based on survey data from across the Marianas, the Saipan population was estimated at 151 (95% CI: 27-370) individuals (Amidon et al. 2011), although this may have been an overestimate (P. Radley in litt. 2021).
On Farallon de Medinilla, the population was estimated in 1996 to be less than 10 individuals (M. Lusk, pers comm., in USFWS 1998). More recent information suggested a population of at least 24 mature individuals (Vogt 2009).
On Anatahan, the population size was suspected to be around 300 individuals in 1988 (Reichel and Glass 1988), 1,150 (523-2,539) individuals in 2000, and 2,928 (1,830-4,685) individuals in 2002, just before the volcanic eruption (de Cruz et al. 2003a). Following the volcanic eruption, the population was thought to be extirpated (Kessler and Amidon 2009). However, 23 individuals were detected during surveys in 2010 (Amidon et al. 2011).
The population on Sarigan was estimated at 423 to 522 birds based on variable circular plot counts (USFWS 1998). In 1997, the Sarigan population was estimated at 677 (545-810) individuals (Fancy et al. 1999). In 2006, the population was estimated at 3,544 (2,404-5208) breeding individuals (Martin et al. 2008). Following surveys in 2010, the population was estimated at 2,135 (95% CI: 1,261-3,250) individuals (Amidon et al. 2011). The larger recent population estimates may be partly due to increased survey effort, and partly the result of ungulate removal (Amadon et al. 2011).
The population on Guguan was estimated in 1986 at 1,500 - 2,200 individuals (Glass and Villagomez 1986). Subsequent surveys indicated a decline, with population estimates of 500 individuals in 1992 (Rice and Stinson 1992) and 305 (172-438) in 2000 (Cruz et al. 2000). However, surveys in 2010 estimated a population of 1,507 (95% CI: 824-2,449) individuals (Amidon et al. 2011).
On Alamagan, surveys in 2010 and analysis using a modelled detection function based on survey data from across the Marianas, estimated the population at 529 (95% CI: 92 - 966) individuals (Amidon et al. 2011). Repeat surveys in 2017 resulted in a population estimate of 114 birds (50-178; Murray et al. 2017).
On Pagan, the population was estimated at 50-150 individuals in 1994 (C. G. Rice, pers. comm. 1994, in USFWS 1998). Following surveys in 2010 and analysis using a modelled detection function based on survey data from across the Marianas, the population was estimated at 147 (95% CI: 28-312) individuals (Amidon et al. 2011), which may have been an overestimate (P. Radley in litt. 2021).
The population size in Agrihan in 2010 was thought to be smaller than ten individuals (Amidon et al. 2011).
On Asuncion, the species was previously considered rare, with a rough population estimate of less than 25 individuals in 1995 (D. Stinson pers. comm. 1995, in USFWS 1998). However, surveys in 2008 and 2010 found a large population, estimated at 1,757 (1,123-2,487), and 5,714 (95% CI: 3,135-8,821) individuals respectively (Radley 2009, Amidon et al. 2011). The 2010 population estimate had a high level of statistical confidence, but assumed that all habitat was occupied, which may not have been the case (P. Radley in litt. 2021).
In Maug, the species was found to be common on all three islands in 1992 (Rice and Stinson 1992), with the population at that time estimated at 50-150 individuals (C. Rice pers. comm. 1994, in USFWS 1998). Following surveys in 2010 and analysis using a modelled detection function based on survey data from across the Marianas, the population was estimated at 544 (95% CI: 308-834) individuals (Amidon et al. 2011), which may have been an overestimate (P. Radley in litt. 2021).
Based on the above figures, the current population for the Mariana Islands is estimated to be in the range 3,700 - 21,900 (roughly equivalent to 2,400 - 14,600 mature individuals), with a best estimate of c.6,000 individuals (roughly equivalent to 4,000 mature individuals).
Summing the estimates for Palau and the Mariana Islands, the global population size is estimated to be in the range 2,600 - 15,400 mature individuals, with a best estimate of approximately 4,500 mature individuals.
The subpopulation structure is not known, but the species has been recorded flying several kilometres between islands (Pratt et al. 1980). It is assumed that there are at least 10 subpopulations in the Mariana Islands and at least two in Palau. The largest island population may be on Asuncion or on Sarigan. On Asuncion, surveys in 2008 and 2009 estimated the population at 1,757 (1,123-2,487), and 5,714 (95% CI: 3,135-8,821) individuals respectively (Radley 2009, Amidon et al. 2011). On Sarigan, the population was estimated in 2006 at 3,544 (2,404-5208) breeding individuals (Martin et al. 2008). Following surveys in 2010, the population was estimated at 2,135 (95% CI: 1,261-3,250) individuals (Amidon et al. 2011). Assuming the populations on Asuncion and Sarigan represent distinct subpopulations, the largest subpopulation is estimated to number 1,123 - 8,821 individuals (roughly equivalent to 740 - 5,900 mature individuals), with a best estimate of 1,757-2,135 individuals, roughly equivalent to 1,200-1,500 mature individuals.
Trend justification
In Palau, surveys throughout the archipelago (excluding Kayangel Atoll) in 1991 led to a total population estimate of 497 individuals (Engbring 1992). Recent surveys have estimated the Kayangel Atoll population to be 108 mature individuals (Olsen et al. 2016), so the total Palau population in 1991 may have been c.440 mature individuals. Repeat surveys in 2005 found that the population in Palau had remained stable in comparison with 1991, with a revised population estimate of 700 individuals (VanderWerf 2007, VanderWerf and Dittmar 2020). A survey of nesting mounds on 122 beaches across Palau (excluding Angaur) in 2011-2013 recorded 173 active nesting mounds distributed across 53 sites, indicated a population of c.346 mature individuals (Olsen et al. 2016). Assuming that the 125 individuals estimated for Anguar in 1992 may equate to roughly 83 mature individuals, the total population in Palau in 2013 may have been approximately 429 mature individuals. Further surveys in the Rock Islands in 2017 suggested that the number of nesting sites may have declined by 5-10% since 2013 (Radley 2019). Since previous surveys indicated a population reduction in the Rock Islands but no overall decline for Palau (VanderWerf 2007), the population in Palau is tentatively suspected to be stable.
In the Mariana Islands, the total population was estimated to number 1,440 to 1,975 birds in 1998 (USFWS 1998). Extensive surveys in 2008-2010 combined with DISTANCE analysis estimated much higher numbers than previously reported, with a total estimated population in the northern islands (Saipan, Sarigan, Guguan, Alamagan, Pagan, Agrihan, Asuncion, and Maug) of 10,727 individuals (95% CI: 6,682—15,445) (Amidon et al. 2011). The higher estimate was believed to be largely due to increased survey effort, including the use of playback surveys, but may also have reflected the removal of ungulates from Sarigan in 1998 (Amidon et al. 2011). However, the use of pooled analysis from data across islands together with assumptions about habitat occupancy may have led to this estimate being too high (P. Radley in litt. 2021).
On Aguiguan, surveys in 1982 lead to a density estimate of 3 birds/km2 and a population estimate of 11 individuals (Engbring et al. 1986). The species was described as uncommon on the island in 1992 (Craig and Chandran 1993), when surveys produced to a density estimate of 4 birds/km2 (Craig et al. 1993), suggesting that this population had remained stable (Stinson 1993). Further surveys in 2000 and 2002 estimated the population density at 160 and 140 birds/km2, and the population size over 0.5 km2 of forest at 80 (43-149) and 72 (34-149) individuals, respectively (Esselstyn et al. 2003). Subsequent research using playback indicated a territory size of 3.76 ha in limestone forest on the island, indicating a population size of 112 individuals (61–206; 95% CI; Kessler and Amidon 2009, Amidon et al. 2011). Counts in each survey were too small to reliably analyse trends (Camp et al. 2012a), but there does not appear to be evidence for a decline.
On Tinian, surveys in 1982 and 1994 did not detect any individuals (Engbring et al.1986, USFWS 1998), but incidental reports from the 1990s suggested that a very small population (<10 individuals) may persist (O'Daniel and Krueger 1999, USFWS 1998). None were detected during surveys in 2008 (Camp et al. 2012a,b), and so any remaining population is inferred to be declining.
Surveys on Saipan in 1982 lead to a density estimate of 1 bird/km2 and a population estimate of 40 individuals (Engbring et al. 1986). Repeat surveys in 1991-1992 lead to an estimated population density of 2-3 birds/km2, and an estimated population size of 14 birds in the native forests of the Marpi region (Craig et al. 1993, Craig 1996). Although the density estimates were higher than those estimated in 1982, this was thought to reflect a difference in the habitats surveyed, and not a population increase (Craig 1996). No individuals were recorded during surveys in other parts of the island where the species was previously recorded, leading to the conclusion that the population on Saipan was declining (Craig 1996). In 1997, the population on Saipan was thought likely to be less than 30 individuals (USFWS 1998). Surveys in the Bird Island Wildlife Preservation Area in 2001 detected only a single individual (de Cruz et al. 2003b), and surveys in the Kagman Wildlife Conservation Area in 2002-2003 found none (de Cruz et al. 2003c). Following surveys in 2009, the Saipan population was estimated at 151 (95% CI: 27-370) individuals (Amidon et al. 2011). This higher estimate is likely to be primarily the result of increased survey effort (Amidon et al. 2011) or false assumptions in the DTSTANCE analysis (P. Radley in litt. 2021), and the population on Saipan is suspected to be declining as a result of ongoing habitat degradation.
On Farallon de Medinilla, the population was estimated in 1996 to be less than 10 individuals (M. Lusk, pers comm., in USFW 1998). More recent information suggested a population of at least 24 mature individuals (Vogt 2009). The trend is not known.
On Anatahan, the population size was suspected to be around 300 individuals in 1988 (Reichel and Glass 1988), 1,150 (523-2,539) individuals in 2000, and 2,928 (1,830-4,685) individuals in 2002, just before the volcanic eruption (de Cruz et al. 2003a). Following the volcanic eruption, the population was thought to be extirpated (Kessler and Amidon 2009). However, 23 individuals were detected during surveys in 2009 (Amidon et al. 2011), and the population is therefore inferred to be increasing.
The population on Sarigan was estimated at 100-200 individuals in 1983 (Pratt 1983). Surveys in 1990 produced a population estimate of 180-270 individuals in the forest habitat (Rice et al. 1990). Concurrent variable circular plot counts produced an estimate of 423 to 522 birds (USFWS 1998). In 1997, surveys estimated densities of 389 birds/km2 in coconut forest and 547 birds/km2 in native forest, and the Sarigan population was estimated at 677 (545-810) individuals (Fancy et al. 1999). There was no significant difference between the estimated densities in 1990 and 1997 (Fancy et al. 1999). In 2006, the population was estimated at 3,544 (2,404-5,208) breeding individuals (Martin et al. 2008). Following surveys in 2010, the population was estimated at 2,135 (95% CI: 1,261-3,250) individuals (Amidon et al. 2011). The larger recent population estimates may be partly the result of increased survey effort, and partly the result of ungulate removal (Amadon et al. 2011), so the population here is inferred to be increasing.
The population on Guguan was estimated in 1986 at 1,500 - 2,200 individuals (Glass and Villagomez 1986). Subsequent surveys indicated a decline, with population estimates of 500 individuals in 1992 (Rice and Stinson 1992) and 305 (172-438) in 2000 (Cruz et al. 2000). However, surveys in 2010 estimated a population of 1,507 (95% CI: 824-2,449) individuals (Amidon et al. 2011). This higher estimate is attributed to increased survey effort (Amidon et al. 2011), and may have been artificially inflated by the methods used in the analysis (P. Radley in litt. 2021), so the population size is still suspected to be declining.
On Alamagan there were few records in the 1980s-1990s, and surveys of a small part of the island in 1995 produced a rough estimate of 30 individuals on the island (D. Stinson pers comm. 1995, in USFWS 1998). The population size was thought likely to have increased since residents were evacuated from the island in 1990 due to seismic activity (Stinson 1993). Following surveys in 2010, the population was estimated at 529 (95% CI: 92 - 966) individuals, with the higher number attributed to increased survey effort (Amidon et al. 2011) and possibly due to the analytical methods used (P. Radley in litt. 2021). Repeat surveys in 2017 resulted in a population estimate of 114 birds (50-178; Murray et al. 2017). The population is suspected to be declining as a result of continuing habitat degradation.
On Pagan, the population was estimated at 50-150 individuals in 1994 (C. G. Rice, pers. comm. 1994, in USFWS 1998). Following surveys in 2010, the population was estimated at 147 (95% CI: 28-312) individuals (Amidon et al. 2011). The population is suspected to be declining as a result of continuing habitat degradation.
Agrihan was reported to have previously had two nesting sites large enough for local people to collect "buckets of eggs", but one of the two areas was lost in the first half of the twentieth century (Stinson and Glass 1992) and the status of the population was unknown in 1998 (USFWS 1998). In 2010, the population size was thought to be less than ten individuals (Amidon et al. 2011). Any remaining population is inferred to be declining.
On Asuncion, the species was previously considered rare, with a rough population estimate of less than 25 individuals in 1995 (D. Stinson pers. comm. 1995, in USFWS 1998). Surveys in 2008 estimated the population density to be 5.56 (95% C. I. 3.553 - 7.871) individuals per hectare, based on records of 35 individuals (Radley 2009). Based on 316 ha of forest on the island, the total island population was estimated at 1,757 (1,123-2,487) individuals (Radley 2009). Repeat surveys in 2010 and the use of DISTANCE analysis put the population size at 5,714 (95% CI: 3,135-8,821) individuals (Radley 2009, Amidon et al. 2011). The larger recent estimates may be partly due to increased survey effort (Amidon et al. 2011), and may have been exaggerated by the analysis (P. Radley in litt. 2021), but the population size is suspected to be increasing.
In Maug, the species was found to be common on all three islands in 1992 (Rice and Stinson 1992), with the population at that time estimated at 50-150 individuals (C. Rice pers. comm. 1994, in USFWS 1998). Following surveys in 2010, the population was estimated at 544 (95% CI: 308-834) individuals (Amidon et al. 2011). The apparent increase is likely due to increased survey effort (Amidon et al. 2011) and the analytical methods used, and the current population trend is unknown.
Overall, recent population data appears to suggest a stable or increasing trend, but further surveys are needed to confirm this. Recent research indicates that the species is likely to be impacted by rising sea levels (Radley 2019, Radley et al. 2021). However, this threat is mainly likely to affect subpopulations in Palau, which holds a minority of the total population.
Megapodius laperouse occurs on Palau and the Northern Mariana Islands (to USA), and is extirpated from Guam (to USA).
In Palau, subspecies M. l. senex occurs on Peleliu, Babeldaob, Angaur, Ngesebus, the Rock Islands (including Ulong, Ulebsechel, Ngeruktabel, Mecherchar, Ngerechong, Ngemelis, Babelchomekang, Ngeanges, Kmekumer, and the Ngerukuid Islands; Olsen and Eberdong 2017), Koror, Malakal, Ngerekebesang, and Kayangel Atoll.
In the Northern Mariana Islands, nominate laperouse is mainly restricted to islands north of Saipan, including Asuncion, Agrihan, Pagan, Alamagan, Maug, Guguan, Sarigan, Anatahan and Farallon de Medinilla (Lusk et al. 2000), as well as Saipan and Aguiguan (Craig and Chandran 1993, USFWS 1998). A remnant population of a few birds may persist on Tinian (Wiles et al. 1987, O'Daniel and Krueger 1999, USFWS 1998), although no individuals were detected during a survey in 2008 (Camp et al. 2009). The population on Anatahan was lost in the early 2000s when all habitat on the island was destroyed by a major volcanic eruption (Kessler and Amidon 2009), but later surveys indicated that the species had recolonised the island (USFWS 2010, Amidon et al. 2011). It is extinct on Rota.
Most remaining populations in the Marianas inhabit areas of volcanic forest and coconut groves on volcanic islands, whereas those present on the limestone islands of Saipan and Aguiguan prefer limestone forest and secondary forest (USFWS 1998). In Palau, most birds inhabit beach strand forests, and only a few nests have ever been found in the upland volcanic forests (Engbring 1992, VanderWerf 2007, P. Radley in litt. 2020). The species is omnivorous, taking a wide variety of foods from the forest floor including insects, crabs and plant matter (Pratt et al. 1980, Engbring 1988, USFWS 1998). Nominate laperouse nests in burrows in sun-warmed cinder fields or geothermally-heated areas (USFWS 1998). Race senex nests in large mounds located primarily in narrow beach strand forests; these are constructed of sand and plant material (Wiles and Conry 2001, Olsen et al. 2012, 2016). A few mounds are also built in upland forest and are made of decayed wood and other plant material.
The main ongoing threats to the species are forest degradation by grazing feral ungulates, forest clearance, human disturbance, and sea level rise due to climate change.
Ungulates are currently present on Aguiguan, Tinian, Saipan, Alamagan, Pagan, and Agrihan (USFWS 2020). Little is known about the extent of ungulate grazing in Palau. On Sarigan, habitat has been severely degraded as a reult of grazing by goats and pigs (Fancy et al. 1999), but goats and pigs were removed from the island during 1998-2000 (Kessler 2002). Surveys in the Northern Mariana Islands in 2008-2009 found that the species had higher densities on islands without ungulates, and that the likelihood of detecting the species on ungulate-free islands was 84% compared to 37% on an island with ungulates (Amidon et al. 2011). However, the majority of the species's population is currently located on islands that are free of ungulates (Amidon 2011, Radley 2019).
Forests on Saipan, Tinian and Aguijan were extensively cleared for sugarcane plantations during the first half of the 20th century (Stinson and Glass 1992). On Sarigan, forest has been cleared for coconut palm plantations (Fancy et al. 1999). Commercial and residential development also contributes to habitat degradation (USFWS 1998). Forest on Saipan was projected to continue to undergo considerable clearance from 2000-2030 to make way for housing development (Stein et al. 2014).
Birds were hunted, and eggs were collected in the past (Pratt et al. 1980, USFWS 1998). Nowadays, the species is rarely hunted, but the eggs are still regularly collected illegally from nest mounds on a limited basis (Engbring 1992, Pratt and Etpison 2008, C. Kitalong pers. comm., in Radley 2019).
In Palau, increased tourist use of beaches has resulted in disturbance to nest sites (Engbring 1992). In the Rock Islands, the species was recorded at lower densities at islands with a higher tourist presence, suggesting an impact of tourism (Radley 2019, Radley et al. 2020).
On all islands, predation on megapodes by introduced predators, e.g. monitor lizard Varanus indicus, rats Rattus spp., and feral cats, dogs and pigs is a threat (USFWS 1998, Pratt and Etpison 2008). Studies in Palau indicate that predation by rats (mainly Rattus rattus) does not have a major impact on the scrubfowl (Radley 2019, Radley et al. 2020). Cats have been introduced to the Rock Islands Southern Lagoon Conservation Area, and are likely to be a significant threat there (T. Hall, pers. comm. 2020, in P. Radley in litt. 2020).
The accidental introduction of the Brown Tree Snake Boiga irregularis from Guam to other islands in the Marianas and to Palau is a potential threat (Stinson and Glass 1992, USFWS 1998). If the snake were to become established on a range island, it could likely lead to extremely rapid declines, as has been the case amongst the endemic avifauna of Guam (to USA) (although the scrubfowl was extirpated from Guam before the arrival of the snake; Wiles et al. 2003). Roadside surveys on Guam indicated a 90% decline in most bird species within 8.9 years (Wiles et al. 2003). Accidental introduction via cargo ships and planes has been the primary mechanism for the spread of the species from Guam to other islands, and all goods received in the Northern Mariana Islands are shipped through Guam, with the majority arriving in Saipan (Colvin et al. 2005, MAC Working Group 2014). There have been over 70 reports of Brown Tree Snake on Saipan, including sightings away from port areas (Rodda and Savidge 2007, MAC Working Group 2014), and the island was previously thought to have an incipient population (Colvin et al. 2005). However, surveys have not demonstrated the establishment of a breeding population on the island (Rodda and Savidge 2007) and there have been no confirmed records of the species on Saipan for 20 years (L. Berry in litt. 2020). Nevertheless, the risk of the establishment of Brown Tree Snake on Saipan remains high. Although efforts are being made to prevent the introduction of the species, it is not possible to detect all snakes in cargo. The potential introduction of the Brown Tree Snake is primarily a threat to the subpopulations on the inhabited Mariana Islands of Saipan and Tinian (Radley 2019), which together contain only a small minority of the global population. Palau has a native species of bird-eating snake, and so the scrubfowl may be behaviourally adapted to this threat (Radley 2019).
A volcanic eruption destroyed the entire megapode population on Anatahan in the early 2000s. Volcanic activity is an ongoing threat on other islands as well, including Asuncion, Pagan, Guguan, Sarigan, Alamagan and Agrihan, and can bury vegetation and nesting areas (USFWS 1998). Over 80% of the population of the Northern Mariana Islands in found on Asuncion, Guguan, and Sarigan, all of which are dormant volcanos that could become active at any time (P. Radley in litt. 2021).
Forests across the species's range are periodically degraded by typhoons. Increased typhoon frequency and intensity as a result of climate change may increase the threat posed by typhoons, especially in Palau (Radley 2019). However, the species is likely to have some resilience to typhoons, and surveys of nesting mounds in Palau following typhoons found that the majority of damaged nesting mounds were quickly restored (Olsen et al. 2016). In Palau, the species is threatened by the loss of coastal nesting habitat due to rising sea levels resulting from climate change, which could lead to significant population declines in the long term (Olsen et al. 2012, Radley 2019, Radley et al. 2021). An analysis of the impact of sea level rise estimated that 33-43% of the species's breeding habitat in the Rock Islands will be lost by 2100 (Radley 2019). Neither typhoons nor sea level rise threaten populations in the Marianas to the same degree because they generally nest at higher elevations (Olsen et al. 2012, Radley et al. 2021).
Conservation Actions Underway
The species was listed as Endangered by the US Fish and Wildlife Service in 1970. In the Marianas, a recovery plan exists and the species is protected by federal and local laws (USFWS 1998). The uninhabited islands of Asuncion, Maug, Uracus and Guguan are wildlife sanctuaries (USFWS 1998), and there are several protected areas on Saipan (MAC Working Group 2014).
Goats and pigs were removed from Sarigan during 1998-2000 (Kessler 2002), and from Anatahan during 2002-2003 (de Cruz et al. 2003a). Rats were eradicated from Ngeanges in 2017 (T. Hall, pers comm, in P. Radley, in litt. 2020), and from the Kayangel Atoll in 2018 (Esposito and Hurrell 2018). Extensive efforts are underway to prevent the accidental introduction of Brown Tree Snake (Boiga irregularis) on Saipan (Colvin et al. 2005). Cargo arriving at sea and air ports in Saipan is checked for snakes and traps have been installed to catch any snakes that are missed (MAC Working Group 2014). Barriers have been constructed at docks on Saipain to allow any introduced snakes to be contained (MAC Working Group 2014). Sniffer dogs have been trained to detect Brown Tree Snakes at Saipan airport (MAC Working Group 2014). Port officers from Saipan have been sent to Guam to receive training on prevention of Brown Tree Snake invasion and a programme has been carried out on Saipan to increase awareness among the general population of the importance of reporting Brown Tree Snake sightings (MAC Working Group 2014).
On the Kayangel Atoll, local people have been trained in monitoring techniques (Palau Conservation Society 2015).
Conservation Actions Proposed
Develop a long-term, standardised monitoring programme across the species's range to monitor population trends. Maintain monitoring to detect the presence of any Brown Tree Snake individuals on the species's range islands (MAC Working Group 2014).
In the Marianas, preserve remnant forest from development and feral ungulates. Remove feral ungulates (cattle, pigs and goats) from Agrihan, Pagan, and Alamagan (Amidon et al. 2011, USFWS 2016). Restore native forests across the species's range. Throughout its range, selectively control cats, rats, and monitor lizards. Continue to implement measures to prevent the establishment of a Brown Tree Snake population on Saipan. Implement an education programme to discourage hunting and collecting of the species and to raise awareness of the species's conservation. Control poaching through enforcement and education measures (USFWS 1998). Protect nesting mounds in Palau from coastal erosion (Olsen et al. 2012).
38 cm. Medium-sized, dark megapode with paler head. Mostly brownish-black with short pale grey crest. Yellow bill, red facial skin showing through thin feathers. Unusually large, dingy yellow legs and feet. Similar spp. Could be confused with dark morphs of Red Junglefowl Gallus gallus (or feral domestic stock). Voice Call a loud keek, song often a duet with one bird beginning a rising and accelerating keek-keek-keek-keek- etc. culminating in a loud kee-keer-kew (Palau) or keek-keer-keet (Marianas), the other answering with a rising cackle that slows near the end. Hints Often shy and secretive, but becomes relatively tame on inhabited islands where protected from disturbance.
Text account compilers
Wheatley, H.
Contributors
Lepson, J., Millett, J., Wiles, G., Camp, R., Gupta, A., O'Brien, A., Mahood, S., Derhé, M., Stattersfield, A., Keane, A., Radley, P. & Davis, R.A.
Recommended citation
BirdLife International (2024) Species factsheet: Micronesian Scrubfowl Megapodius laperouse. Downloaded from
https://datazone.birdlife.org/species/factsheet/micronesian-scrubfowl-megapodius-laperouse on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.