ARTICLES ON HAWAIIAN
BIRDS AND BIRDWATCHING AND OTHER
PACIFIC WILDLIFE
The Micronesian Megapode
The Megapodes comprise twenty-two different species and are distributed throughout Australia, Papua New Guinea, The Philippines, the Nicobar Islands, Indonesia and several southwest Pacific islands. Sometimes they are referred to as "thermometer birds", as some of the species incubate their eggs in constructed mounds of rotting vegetation, which they manipulate in order to regulate the temperature. Other species in the family dig burrows in warm sand to incubate their eggs.
They are the only known birds which use heat sources, other than the body, to incubate their eggs. When the young birds hatch they are fully able to defend for themselves and receive no parental care. Megapodes are quite heavy-bodied birds and forage on the forest floor, where they search for insects, seeds and fruit. All members of the Megapode family can fly, but most move around primarily by walking.
Drawing, right, from United States Fish and Wildlife Service Recovery Plan for the Micronesian Megapode. 1998. Original drawing by H. Douglas Pratt.
The Micronesian Megapode (Megapodius laperouse laperouse) is found in the Mariana Islands and Palau. The Mariana Islands host an avifauna of Melanesian, Moluccan/Celebesian, Philippine and Palearctic origins. The avifauna of the area is in the second of two human-caused bird extinction events. The first wave of extinction occurred about 2,000 to 4,000 years ago when the first Polynesians arrived. The huge change in population and exploitation of the islands resulted in extinction for many species, and it has been estimated that more than half of the original avifauna of the Mariana Islands became extinct during that time (Steadman 1992).The second wave of extinction came when the first Europeans arrived in the 16th century. The introduction of alien species, exploitation and habitat destruction all took their toll on the native species.
The Micronesian Megapode, called "sasangai" in Chomorro and "sasangal" in Carolinian, is a pigeon-sized bird of the forest floor. The species was extirpated from all the large southern Mariana Islands except Tinian in the 19th and early 20th centuries. A small remnant population persists on a few other islands - Aguiguan, Tinian, Farallon de Medinilla, as well as a very small population reintroduced on Saipan. The Megapode only remains in quite large numbers on the smaller, uninhabited northern islands of Anatahan, Sarigan, Guguan, Pagan, Maug, Almagan, Ascuncion and possibly Agrihan. The total population for the species is about 1,440 to 1,975 birds in the archipelago.
The Micronesian Megapode was federally listed as endangered on June 2nd 1970 (35 FR 8491-8498). The species is also listed as endangered in the International Union for the Conservation of Nature (IUCN) Megapode Action Plan (Dekker et al. 1995) and a s threatened by Birdlife International (Collar et al. 1994).
The Micronesian Megapode was first described by Quoy and Gaimard (1824 to 1826) from a single specimen obtained on Tinian by Berard during a expedition on the Uranie in December 1820. Megapodes collected in the Palau Islands were originally described a s a separate species, Megapodius senex, by Hartlaub, but were considered a race of M.l. laperouse by later researchers. Dekker et al. (1995) however still differentiate between the two.
The Micronesian Megapode is about the size of a pigeon, with an average weight of about 350 grams (Glass and Aldan 1988). It has a dark gray-brown to black body plumage and an ash gray head with a slightly darker, short crest. The flight feathers and short tail are grayish-black and the wings are short and rounded. Around the eye, ear and throat the feathering is sparse or absent, which reveals red skin and a red gular skin patch when the neck is extended. The species often adopts a rather hunched posture. The bill is yellow with the upper mandible brown to black at the base. The legs and feet are sturdy and yellow, with dark gray-black joints and upper surfaces. The iris is orange-brown to dark brown (Baker 1951, Jones et al. 1995)
The birds have several different calls and duetting is performed on a regular basis. The phenomenon of duetting birds is correlated with year-round territoriality and prolonged monogamous pair bonds (Farabaugh 1982). Duets may function as a joint territory proclamation between mates and neighbouring pairs or to advertise the existence of a pair bond, discouraging single birds from entering the territory and searching for a mate.
It seems that nesting may occur year-round as chicks have been observed at different times of the year, and mounds have been constructed year-round too. The exact pattern of mating and nesting times/periods is at present unknown.
According to Dekker (1990) there are four Megapode incubation strategies.
1). Burrow nesting at sun-exposed beaches or cinder fields.
2). Burrow nesting at geothermal sites.
3). Mound-building, which uses heat of decomposition of vegetation.
4). Burrow nesting between the roots of trees (decompositional heat).
In Micronesia Megapodes apparently utilise all four methods for incubation whereas most
other species use only one or two. On Guaguan, the species lays eggs in dark solar-heated cinders at a communal
nesting site (Glass and Aldan 1988). The species also utilised this method on Pagan until a volcanic eruption in
1981 buried the site. On Palau the species builds a large mound of sand and small amounts of vegetation, and these
mounds may be used by and built by several birds. A full account of nesting behaviour of the Micronesian Megapode
can be found in both Dekker et al. 1995 and the Recovery Plan for the Micronesian Megapode (USFWS 1998).
Right: Map of the Mariana Islands.
Based on the distribution of Magapodes it appears that they are quite capable of flying for quite some distance, even over water. In Palau the species has been observed flying for several kilometres between islands (Pratt et al. 1980). It is quite likely that birds fly between the closer islands such as Saipan and Tinian and Tinian and Aguiguan, which are only a few kilometres apart; it is unlikely however that birds fly the longer distance (30 - 60 km) between the adjacent northern islands, although rather surprisingly Falanruw (1975) observed a bird on Uracas, an active volcano with no forest habitat!
The Micronesian Megapode generally remains in the forest, both along the coast and inland. On Saipan they are restricted to the native limestone forest remnants near the Marpi Cliffs. In 1988 Glass and Aldan reported that 28 percent of sightings were in introduced Tangantangan forest (Leucaena leucocephala), but after Typhoon Kim in 1986 birds did not use this habitat as it had become a dense, impenetrable tangle. Limestone forest appears the most popular nesting habitat in the islands and most are recorded in native forest or in small open clumps of introduced species. On Sarigan birds are often seen in coconut forest as well as native vegetation.
The Micronesian Megapode was historically a widespread species in the Marianas and has been recorded on all the islands, although it has been stated by some authorities, including Glass, that the widespread distribution may be partly human biased, with humans moving birds to different areas as a source of eggs and food.
Status on each island:
The species currently found on twelve islands in the Mariana Islands, assuming that birds are still present on Agrihan but not present on Uracus. The bulk of the population occurs on eight islands, all north of Saipan. The total number of individuals concerned is estimated at between 1,440 and 1,975.
Guam
The Megapode has always been rare on this island, since at least the time of the first Europeans. The species was reported in the early years of the twentieth century and it may have survived into the 1930's (Linsley 1935) but Baker (1951) stated that it was probably extinct and none have been observed in recent years, despite extensive surveys.
Rota
Between 1824 and 1826 Quoy and Gaimard believed the species to be extinct on this island, but in 1888 Marche collected the species here and so it was either rare or introduced between 1826 and 1888. Despite the occasional report the species is currently presumed to be extinct on Rota.
Aguiguan
Present in small numbers with reports in the 1930's, 1950's, 1980's and 1990's. Five birds were reported to have been collected here and taken to Japan (Takatsukasa 1932-1938). Surveys in 1982 estimated 11 birds present, and recent reports indicate little change in the species status here.
Tinian
It was reported as rare here in 1820 and it was not reported from here in 1945, but there were second-hand reports of them, although none was found in surveys in 1994 or 1996. One was reported in 1985 but subsequent searches of good habitat did not reveal any birds. Local reports continue however and it may be that a few individuals are still present.
Saipan
The species was once common on this island and 23 were collected by Marche in 1887, although he stated that he thought they would become extinct due to excessive hunting. Although birds were not found in the intervening years a small population was found by Pratt and Bruner (1978) in the northern part of the island. These birds (or their eggs) were probably transported their from the northern islands by local residents (Glass and Aldan 1988). In 1982 the population was estimated at 40 birds and in 1988 25 to 40 birds were estimated to survive. A more recent estimate of just 14 birds suggests that the numbers have fallen and the species could be in trouble (Craig 1996). Reproductive success on the island is reported as being probably low, as few immature birds are seen. A survey in 1997 found very few birds (too few detections for a population estimate), but fewer than thirty birds are thought to survive.
Alamagan
The species was present in the 1930's but little information is available for later years. Local residents report that birds nested on the northeastern and southeastern parts of the island into the 1950's and 1970's (Reichel et al. 1988). In 1988 however none were recorded in the southern section and in 1990 none were recorded anywhere on the island. In 1995 a population of 30 birds was estimated for the island, perhaps helped by the evacuation of human inhabitants during a period of increased seismic activity in 1990.
Pagan
The species was first collected here in 1887 and the species was common in the 1950's and 1960's and local residents reported four nesting areas. One of these areas was buried by volcanic cinders during an eruption in 1981, and other vegetative areas were buried too. Birds have not been resighted in the northern part of the island where the volcano erupted but birds were still common in the southern areas during the 1960's and 1970's. Birds have still not been observed in the northern part of the island (by 1997) but they are still found in the southern portion, where there are at least seven locations with birds. Feral animals and Monitor Lizards pose a large threat to birds on this island.
Agrihan
Birds were first collected here in 1889, but many eggs were collected from the nesting areas throughout the twentieth century, and local residents still took eggs into the 1970's. Apparently Monitor Lizards (Varanus indicus), cats (Felis catus) and dogs (Canis familiaris) also prey upon the eggs. Today, perhaps due to exploitation and predation, the numbers are probably reduced but still present. No current status is available for this island, although the island is large and quite rugged and able to support the species.
Asuncion
They were first reported on this island in the 1940's and still survive today in small numbers, with only one or two reported on recent trips. A population estimate of less than 25 individuals has been offered based on a survey of a small part of potential habitat.
Megapodes were not reported on Anatahan, Sarigan, Guguan, Maug or Uracus until the early 1970's and only in recent years on Farallon de Medinilla, although survey extent before the '70's in these areas in unknown. Today the species is reported as common on all three islands in Maug, both in forest and scrub habitat. Maug is a protected sanctuary and is free of feral animals. An estimate of 50 to 150 birds may be present today. On Uracus the species has not been reliably sighted. On Farallon de Medinilla the species was observed in 1996, when four birds were seen, no nesting has been observed but there is suitable nesting habitat present. An estimate of ten or less birds for the island. On Anatahan Glass and Aldan (1988) estimated a population of 300 birds based on detections on the south shore and west end of the island. The numbers here have no doubt been increased by the human evacuation of the island in 1990, however it is almost certain that the island will be recolonised in the future. Sarigan's population of Megapodes was estimated at 100 to 200 birds by Pratt in 1983 and a survey in 1990 estimated 180-279 birds, distributed throughout the forest habitat. Variable circular plots conducted at the same time produced an estimate of 423 to 522 individuals. A survey in 1998 estimated between 545 and 810 birds (Fancy et al. 1998), the highest known population in the Mariana Islands.
Dekker et al. (1995) states that "in Palau M.l.senex recorded from volcanic islands of Babelthaup and Korror, and from coralline islands of Kayangal group, Arakabesan, Urukthapel, Aulong, Eil Malk, Garakayo, Ngabad, Ngesebus, Ngerukeuid and Kmekumer islands, Gayangas, Arumidin, Peleilu, and Angaur, as well as many offshore islets. Status: rare or extinct already in late nineteenth century on larger inhabited islands of Babelthuap, Arakabesan, and Korror; in 1945, mainly restricted to isolated offshore islets, with few birds elsewhere, for example 20-30 on Garakayo, 5-10 on Ngabad, 10-20 birds on Peleliu, and fewer than ten on Angaur (Baker 1951). At present common south of Korror.. Conservative estimates on small islands ranged from 0.76 to 1.60 birds per hectare, or 69 to 103 birds per km squared for Ngerukewid and Kmekumer in 1988, with an average of 1 mound per 10-15 birds (Wiles and Conry 1990). Also common in southern Angaur in 1991 (G.Wiles, in litt.)."
Obviously there are numerable threats to the species in the Marian Islands, such as predation, habitat destruction, nest destruction, volcanic eruptions and poor population recruitment, however with a little protection of suitable habitat and education to locals about egg predation the population is a good candidate for recovery, and a stable and flourishing population could be achieved in just a few years. The threat of new alien species being accidentally introduced to the islands must also be taken very seriously.
Table 1. Current Population of Micronesian Megapodes in the Mariana Islands.
| Island | Approximate Land Area | Estimated Population Size | Recent Population Trend |
| GUAM | 541 | 0 | N/A |
| ROTA | 85 | 0 | N/A |
| AGUIGUAN | 7 | 10-15 | Stable |
| TINIAN | 100 | <10 (*1,*4) | Stable |
| SAIPAN | 122 | 10-25 | Decline (*2) |
| FARALLON de MEDINILLA | 2 | <10 | Decline (*3) |
| ANATAHAN | 32 | 200-300 (*4) | - |
| SARIGAN | 5 | 545-810 (*5) | Increase (*5) |
| GUGUAN | 3.7 | 500 (*4) | Decline (*6) |
| ALAMAGAN | 11 | <30 (*4) | Increase (*7) |
| PAGAN | 48 | 50-100 (*4) | Decline (*8) |
| AGRIHAN | 47 | ? | Decline (*9) |
| ASUNCION | 7 | <25 (*4) | - |
| MAUG | 2.5 | 50-150 | - |
| URACUS | 2.5 | 0 | - |
*1 (D.O'Daniel, pers. comm. 1997)
*2 May have declined since 1982.
*3 Probable population decline due to military activities.
*4 These figures are rough estimates based on surveys of a small portion of potential habitat on the island.
*5 Data from recent surveys indicates a general population increase.
*6 Apparent decline after Glass's 1986 visit.
*7 May be recovering after severe decline; several were detected in 1992, but not detected on previous trips.
*8 A productive nesting area was buried by cinders in 1981.
*9 The fact that a nesting area near the village was destroyed early in the 20th century, and a nesting area described by Ludwig (1979) has never been relocated indicate that megapodes may be extirpated from Agrihan.
Right: Stages of construction and structure of a Megapode mound. (From Dekker et
al 1995, adapted from Rowley 1974.
Below: Structure of the mound of a Megapode, showing compacted material and the burrows leading to the egg chamber. (From Dekker et al. 1995.)
Below: Megapode nest in the rainforest. The mound would consist of compacted soil and leaf litter but only the very top of the mound would be used as an incubator. The mound may have been used annually for over fifty years, probably by a succession of pairs. The scale marker is 4.5 metres in height. (From Dekker et al 1995.)
References
BAKER, R.H.. 1951. The avifauna of Micronesia, its origin, evolution and
distribution. Univ. Kansas Publ. Mus.Nat. Hist. 3: 1 -359.
COLLAR, N.J, M.J. CROSBY, and A.J. STATTERSFIELD. 1994. Birds to watch 2: The World List of Threatened Birds. Birdlife Conservation Series No.4. Birdlife International, Cambridge, U.K.
CRAIG, R.J.1996. Seasonal population surveys and natural history of a Micronesian bird community. Wilson Bulletin. 108: 246-267.
DEKKER, R.W.R.; JONES, D.N.; C.S. ROSELAAR and B. van PERLO. 1995. The Megapodes Megapoidiidae. OUP, Oxford, U.K.
FALANRUW, M.C.V..1975. Distribution of the Micronesian Megapode Megapodius laperouse in the Northern Mariana Islands. Micronesica 11:149-150.
FANCY, S.G., R.J. CRAIG and C.W. KESSLER.1998. Forest bird and fruit bat populations on Sarigan, Mariana Islands. Micronesica.
FARRABAUGH, S.M. 1982. The Ecological and social significance of duetting. In Kroodsma, D.E. and E.H. Miller, eds. Acoustic communication in birds, Vol 2. pp.85-124. Academic Press, New York.
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LINSLEY, L.N. 1935. Curious things about Guam: the mountain chicken. Guam Recorder 12:249-250, in Baker 1951.
LUDWIG, G.M. 1979. Fish and Wildlife Concerns and Recommendations for Northern Mariana Islands based on July 1978 Field Trip. Unpub. Report, U.S. Fish and Wildlife Service, Honolulu.
PRATT, H.D. and P.L. BRUNER. 1978. Micronesian Megapode rediscovered on Saipan. Elepaio, 39:57-59.
PRATT, H.D., J. ENGBRING, P.L. BRUNER, and D.G. BERRETT.1980. Notes on the taxonomy, natural history, and status of the resident birds of Palau. Condor 82:117-131.
QUOY, J.R.C. and P.J. Gaimard. 1824-1826. Voyage autour de monde. Enterpres par ordre du roi. Execute sur les corvettes de S.M. I'Uranie et la Physicience pendant les annees 1817, 1818, 1819, et 1820. Par M. Louis de freycinet, Capitaine de Vaisseax. Zoologie. Paris, Chez Pillet Aine, Imprimeur-Libraire: 712p. in Baker 1951.
REICHEL, J.D. and P.O. GLASS.1988. Field trip Report: Anatahan, 27-29 September. CNMI Division of Fish and Wildlife, Saipan.
STEADMAN, D.W.1992. Extinct and extirpated birds from Rota, Mariana Islands. Micronesica 25: 71-84.
TAKATSUKASA, S. 1932-1938. The Birds of Nippon. H.F. & G. Witherby, London.
UNITED STATES FISH AND WILDLIFE SERVICE. 1998. Recovery Plan for the Micronesian Megapode (Megapodus laperouse laperouse). U.S. Fish and Wildlife Service, Portland, OR. 65 + pp.
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Christian Melgar. Worthing, West Sussex, UK. 2002.
