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J. Raptor Res. 44(1):12–18 E 2010 The Raptor Research Foundation, Inc.

THE NEST, EGGS, AND DIET OF THE PAPUAN FROM EASTERN

ROBERT E. SIMMONS1 DST/NRF Centre of Excellence, FitzPatrick Institute, University of Cape Town, Rondebosch 7701, South

ABSTRACT.—The (Circus spilonotus spilothorax), currently classified as a of the Eastern Marsh-Harrier (C. spilonotus), is endemic to the island of New Guinea and may be in need of conservation attention because of threats from burning. I here detail the discovery of the first known nests in lowland Papua New Guinea and provide egg dimensions and prey data. Both nests were initiated in early April, in damp rank grassland, and contained three small chicks in mid-May. The only egg measurements, combined with one previously published record, suggest large egg volume and concomitant large female body size (estimated to be ca. 890 g). At this size, this may be the world’s largest harrier. Fire destroyed both nests within 5 wk of their discovery. An atypically slow foraging style and a preponderance of game and large rats (Rattus spp.) in the pellets and prey remains are consistent with large body size. Further studies of the ’s ecology and breeding are needed for a comprehensive understanding of its and threats to its population.

KEY WORDS: Papuan Harrier; Circus spilonotus spilothorax; Eastern Marsh-Harrier; Circus spilonotus; body size; diet; egg size; foraging; Papua New Guinea.

NIDO, HUEVOS Y DIETA DE CIRCUS SPILONOTUS SPILOTHORAX DEL ESTE DE NUEVA GUINEA

RESUMEN.—Circus spilonotus spilothorax, actualmente clasificada como una subespecie de C. spilonotus,es ende´mica de la isla de Nueva Guinea y puede necesitar medidas de conservacio´n debido a amenazas provenientes de la quema de pastizales. Aquı´ detallo el descubrimiento de los primeros nidos encontrados en las tierras bajas de Papu´a Nueva Guinea y brindo las dimensiones de los huevos y datos de las presas. Ambos nidos fueron iniciados a principios de abril en pastizales hu´medos y albergaron tres pequen˜os pichones a mediados de mayo. Las u´nicas medidas de los huevos realizadas en este estudio, combinadas con un registro publicado anteriormente, sugieren un volumen grande del huevo y un taman˜o concomi- tantemente grande del cuerpo de la hembra (estimado en ca. 890 g). Segu´n este taman˜o, podrı´a ser el gavila´n ma´s grande del mundo. El fuego destruyo´ ambos nidos dentro de las cinco semanas de su descu- brimiento. Un estilo de forrajeo atı´picamente lento y una preponderancia de aves de presa y ratas (Rattus spp.) de gran taman˜o en las egagro´pilas y en los restos de presas son consistentes con un taman˜o de cuerpo grande. Se necesitan ma´s estudios sobre la ecologı´a y la reproduccio´n de esta especie para alcanzar un conocimiento amplio de su estado de conservacio´n y de las amenazas a su poblacio´n. [Traduccio´n del equipo editorial]

Avifaunal studies on the island of New Guinea of breeding seasons, conservation issues, and behav- began with numerous ornithological expeditions ioral ecology of other New Guinea birds have (e.g., Rand 1942, Mayr and Gilliard 1954, Gilliard emerged (Bell 1982a, 1982b, Dumbacher et al. and Lecroy 1961, 1967, Hoogerwerf 1964, Diamond 1992, Symes and Marsden 2005, Marsden et al. 1972) but have focused primarily on the colorful 2006) including that of the poorly known endemic Birds of Paradise (Paradisaeidae: Mack and Wright raptors (Legra 2005). A bird almost entirely over- 1996, Frith and Beehler 1998). With the exception looked in this increased research activity is the Pap- of studies by Diamond (1985) and Heads (2002), uan Harrier (Circus spilonotus spilothorax). I here this has often been at the exclusion of other endem- present data on the breeding and diet of the Papu- ic fauna. However, in the last three decades, studies an Harrier, an endemic raptor species for which occasional sightings, a single egg record, and pho- tographic records of captive birds represent most of 1 Email address: [email protected] our knowledge (Coates 1985, Coates and Peckover

12 MARCH 2010 NESTS AND DIET OF PAPUAN HARRIERS 13

2001). Moreover, this birds’ species status is also bird (if known). I simultaneously recorded the hab- controversial, with several authorities believing it itat over which they foraged and the number of prey to be a subspecies of the Western Marsh-Harrier strikes in relation to successful captures. The bird’s (Circus aeruginosus) or Eastern Marsh-Harrier (C. subsequent behavior was followed using 8.5 3 42 spilonotus; Brown and Amadon 1989, Ferguson-Lees binoculars. Food-carrying male harriers typically and Christie 2001, BirdLife International 2004). pass their prey to a dependent female or young in Other authors, perhaps more familiar with it in an aerial food pass (Hamerstrom 1986, Simmons the field, have recommended full species status 2000) and in this way I found both sites following based on its endemic residence status, dif- each female’s return to her nest. ferences, and the fact that Eastern Marsh-Harriers I visited the two nests on two occasions: (1) to do not visit the island of New Guinea (Simmons record the eggs or young upon first finding the 2000, Coates and Peckover 2001, I. Fefelov pers. nest, and (2) to note progress, take blood samples, comm., J.-M. Thiollay pers. comm.). and to measure eggs and chicks using Vernier calli- During an expedition to the island in 2007, I sur- pers. A third visit was made by independent observ- veyed sites likely to hold harriers and undertook ers to record nest success or failure. During nest road counts and area assessments to determine visits, I collected any pellets regurgitated in the nest the first population estimate and threats to this spe- and also searched the area below favored perch sites cies (Simmons and Legra 2009). I here describe (especially isolated trees) for pellets. At both nests, I details of the and dimensions of the two assessed prey remains in chick crops by gently push- nests, and provide the first description and photo- ing remains into the gape and removing them for graphs of the eggs and chicks, as well as notes on examination and photography. All regurgitated the diet and hunting of this poorly known endemic contents were then re-fed to the chicks. Photo- raptor. Other details may be found in Simmons and graphed material was identified by K. Legra (2009). Aplin of the Commonwealth for Scientific and In- dustrial Research Organization, , and bird STUDY AREA AND METHODS material by B. Beehler of the Smithsonian Institute, Surveys for this species in Papua New Guinea Washington, DC U.S.A. (PNG) were undertaken in April–May 2007 to look for breeding birds in the eastern highlands cen- RESULTS tered on Goroka (6u059S, 145u259E) and the north- Discovery and Dimensions of First Nests. No eastern lowlands of the Ramu and Markham valleys nests were found in the highlands around Goroka, (5u57.0459S, 145u54.3309E). I searched for breeding but two nests were found in lowland Papua New birds in areas where most sightings had been report- Guinea (Table 1). Both were in damp areas, domi- ed previously (Coates 1985, pers. comm.) and more nated by tall rank grass and entirely shaded from recently from biologists and birding tour operators the sun by overhanging vegetation, and invisible (e.g., B. Beehler, P. Gregory, R. Heinsohn, and R. to the observer from .2 m. Both nests were found James pers. comm.). Road surveys comprised two following food transfers from male to female. observers travelling at variable speeds up to 80 km/ One nest contained two small downy nestlings hr and recording all raptors seen per km in lowland and one unhatched egg (Fig. 1, 13 May 2007), and highlands. Area-specific searches were carried which later hatched, making three nestlings total; out at three localities (1) Mt. Hagen, particularly the second nest had three small downy nestlings the protected airfield (5u469S, 144u179E; 1800– when first found on 15 May 2007. The only egg 2800 m asl), (2) Goroka, including the airfield found in Nest 1 was a typical dirty-white harrier and surrounding (1500 m asl), and (3) egg with large dimensions of 49.18 mm in length a 50-km stretch of lowland valley in the Ramu and and 43.17 mm in width. Both nests showed asyn- Markham valleys centered on Waterais (5u579S, chronous hatching, with the two older nestlings sim- 145u549E; 400–500 m asl). ilar in size and development, and a third apparently To locate nests, I observed the foraging behavior 3–4 d younger. In Nest 2, the youngest nestling of focal birds from a slowly moving vehicle or an appeared subordinate, with some down missing elevated area, until a prey-strike was observed. I re- around its crown, suggesting sibling aggression. corded the target species, the outcome of the forag- Food was always found in the nests during four ing attempt, and the sex and age of the foraging (mid-morning) visits and the crops of nestlings were 14 SIMMONS VOL. 44, NO.1

Table 1. Nest dimensions and contents of two Papuan Harrier nests from the Ramu and Markham valleys, Papua New Guinea, May 2007.

DATE ESTIMATED FIRST NEST LOCATION [ALTITUDE] FOUND EGG DATE1 CONTENTS NEST AND VEGETATION DETAILS No.1 Markham 6u09.7159S, 13 May 6 April 07 1 egg, 2 small 1.0-m-high reeds shading nest; nest Valley 146u08.4949E downy nestlings 50 3 50 cm, 25 cm deep; on damp [404 m asl] ground; made of dry grass; well concealed in grassland No.2 Ramu 5u57.0459S, 15 May 2 April 07 3 small downy 1.2-m-high reeds shading nest; nest (Gusap) Valley 145u54.3309E. nestlings 75 3 52 cm, 25 cm deep; on damp [510 m asl] ground; made entirely of dry grass; well concealed on river floodplain

1 Based on assumed 31 d incubation (Simmons 2000) and the relative sizes of the chicks. always full. Both adult pairs flew overhead, alarm- both nest sites in June 2007 (L. Legra pers. comm., calling, and then perched in nearby trees to contin- P. Limu pers. comm.). ue calling until I left the area. Other nesting areas were likely present in the Neither nest was successful because the frequent Ramu Valley, as I observed sky-dancing displays (Ha- grassland fires that sweep the lowlands at the start of merstrom 1986, Simmons 2000) by at least two grey the dry season (Simmons and Legra 2009) burned males and one melanistic male within 2 km of Nest

Figure 1. First published photograph of Papuan Harrier nestlings (approx. 2 and 4 d old), with an unhatched egg, taken in the Markham Valley, eastern Papua New Guinea. The egg hatched 2 d later. Quail remains are visible bottom left. MARCH 2010 NESTS AND DIET OF PAPUAN HARRIERS 15

Table 2. The diet of Papuan Harriers in the Eastern highlands and lowlands of Papua New Guinea from prey strikes, prey remains, and pellets recovered from nests or perch sites.

DATE AND OTHER LOCALITY RECORD MAMMAL BIRD PREY HABITAT Goroka Airport 28 April, PS1 Mouse — — Shortcut grass Hagen Airport 3 May, PS Quail (Coturnix sp.) Grass/bush Hagen Airport 4 May, PS Mannikins (Lonchura sp.) Grassland Hagen Airport 4 May, PS Lewin’s Rail Rallus pectoralis Long damp grass Hagen Airport 4 May, P Quail (Coturnix sp.) Grassland Hagen Airport 7 May, R Pied Chat Saxicola caprata, or Willie Grassland Wagtail Rhipidura leucophrys Hagen Airport 7 May R Shortcut grass Ramu Valley 13 May PS Quail (Coturnix sp.) Sugarcane/ grass Ramu Valley 14 May 2P Rattus exulans Passerine bird skull Grassland Nest 2 Ramu Valley 14 May 4P 4 3 bird unknown Grassland Nest 2 Ramu Valley 15 May R Rattus sp. Grassland Nest 2 Markham Valley 15 May R Rattus rattus/R. Passerine feather Grassland steini Nest 1 Ramu Valley 16 May C Foetal quail, quail egg Grassland Nest 2 Totals: Small : 4 (22%); birds: 13 (72%); : 1 (6%)

1 PS 5 Prey strike; P 5 pellet; R 5 remains; C 5 crop content.

2. The displays included typical large ‘‘U’’s per- buildings and traditional villages in the lowlands, formed rather slowly relative to other harriers, but suggesting little human persecution. were also accompanied by calling and descending Combining prey data from observed successful flight into likely nest areas (abandoned sugarcane strikes (n 5 5), prey remains and crop contents (n fields with 2-m-high vegetation). Females were at- 5 5), and pellets (n 5 7), I determined that birds tracted to these displays, but no nest building was were the most numerous prey items (n 5 13; 72%), subsequently seen in the short period available. followed by mammals (n 5 4; 22%), and one frog Diet and Foraging. I observed .40 hr of harrier (Table 2). foraging behavior. All foraging harriers were record- One dark brown adult male captured a Coturnix ed over rank or short grassland, and they were par- quail while quartering an old sugarcane field. He ticularly attracted to fires, along with numerous appeared to flush the bird and followed it 30–40 m Black Kites (Milvus migrans) that were also hunting before capturing it on the ground and eating (or fleeing prey. Harriers typically flew slowly about 4– discarding) the head. I followed the bird ca. 2.6 km 5 m above both long and short grasses, and tended back to his nest, where following a food transfer to to wheel and stoop on prey, rather than strike rap- the female, I recovered and identified the prey. idly from lower altitudes as do other harriers. This Other Coturnix quail remains were found in nests, foraging style suggests large body size and low agil- including eggshell and fetal remains. A perched ity. Two birds, an adult male and a subadult male, harrier in the highlands apparently heard bird prey were observed foraging close to gardens and tradi- and flew 10–15 m and killed a juvenile Lewin’s Rail tional villages in the highlands, and both male and (Rallus pectoralis) in dense, wet scrub. Only two female harriers were observed close to modern bouts of passerine-hunting were seen: immature 16 SIMMONS VOL. 44, NO.1 male harriers flew low and fast at mannikins (Lonch- egg size. More samples are required and direct mea- ura spp.), but both were unsuccessful. However, two surements of adult birds, particularly their mass, are sets of passerine feathers at nests suggested that needed. Papuan Harriers are capable of capturing such agile Diet. Given the large number of small mam- prey. mals in Papua New Guinea available as potential Birds foraging at the two recently-mown airstrips prey to the Papuan Harrier (Flannery 1995), it may have been targeting immobilized or recently was initially surprising that mammalian prey, com- killed amphibians. One slightly dried frog specimen mon in the diet of other Circus species, were was recovered from a foraging male. poorly represented in the small samples from both highland and lowland harrier sites. However, DISCUSSION larger harriers, especially the marsh harriers, tend Egg Volume and Female Size. This paper provides to take large birds such as coots and details of the eggs and first photographic records of ducks (Baker-Gabb 1986, Bavoux et al. 1989, chicks for this endemic raptor on Papua New Guin- Clarke 1995), whereas smaller harriers tend to ea, and suggests that it appears to be a large island specialize in small mammals, , and fledg- harrier. The calculated volume of the egg mea- ling birds when they become available (Barnard sured, according to the equation Volume 5 L 3 et al. 1987, MacWhirter and Bildstein 1996, Ar- B2 3 0.51 (Hoyt 1979), was 46.74 cc. This volume royo 1997). Although these dietary trends for was much larger than the only other (unhatched) the Papuan Harrier may arise from its large body egg reported prior to this study (32.47 cc; R. Camp- size, it may also be that small mammal prey are bell in Coates 1985). However, in an effort to pre- well concealed in the long and luxuriant grass dict average female body mass, I averaged the egg typical of the high-rainfall savannas of tropical volumes for use in the equation: Body mass 5 89.91 New Guinea. This may also explain why Papuan 3 10(0.02513egg volume). This relationship was derived Harriers are so attracted to fires, which reveal and from nine of the world’s 16 harrier species and was possibly incapacitate small mammals in the grass- highly significant (r2 5 0.98, P , 0.01; Simmons lands. However, as a caveat, I note that my sam- 2000). The calculated female body weight was ple size was very small, and based on a limited 886 g. number of birds as well. Knowledge of the com- The estimated female mass was marginally higher plete diet of the species in the breeding and than that of the female Australasian nonbreeding seasons awaits larger samples from (Circus approximans; 880 g), currently considered the highlands and lowlands. the world’s heaviest harrier (Baker-Gabb 1986, Sim- Conservation. The two nests and their reported mons 2000). This suggests the Papuan Harrier is the contents represent the second and third nests ever heaviest of the world’s harriers. An equally limited reported, and the first published photographs of set of museum specimens (Nieboer 1973) of 92 mm eggs and downy nestlings (Fig. 1). The blood sam- (female tarsus) and 409 mm (female wing chord) ples collected at one nest that was subsequently lost suggest the Papuan Harrier is among the largest of to fire also constitute the first DNA samples for this the world’s harriers. This is not unexpected for an species; the samples will be used to examine the island species that also occurs in cool highland hab- phylogenetic placement of the species in the Circus itat. Although these calculations suggest large body tree and to inform the species/subspecies debate. size, they are based on only two widely divergent egg Further data are required for this poorly known volumes. The egg reported by Campbell (in Coates island endemic, given the small estimated popula- 1985) was small and unhatched. Given that small tion size of 3600 adults and the threat that grass- egg size can affect egg hatchability in harriers and land burning poses to breeding birds. The data small eggs are associated with low food levels (Sim- need is urgent, given that climate change threatens mons 2000), the unhatched egg reported by Camp- to increase wildfires in a future hotter, drier climate bell may have been smaller than typical. However, in Papua New Guinea (Simmons and Legra 2009). the egg reported here was the third to hatch and ACKNOWLEDGMENTS therefore assumed last laid. Third eggs are often the I am indebted to L. Legra of the Wildlife Conservation largest in marsh-harrier clutches (Simmons 2000), Society for logistical and field support before and during so by chance the only two eggs known for this spe- this study. J. Robbins of the National Research Institute of cies may well be at the extremes of the variation in Papua New Guinea facilitated permits from the Depart- MARCH 2010 NESTS AND DIET OF PAPUAN HARRIERS 17 ment of Environment and Conservation. Prof. L. Hill al- DIAMOND, J.M. 1972. Avifauna of the eastern highlands of lowed me affiliation with the University of Papua New New Guinea. Publication of the Nuttall Ornithological Guinea. J. and M. Simmons and D. Scott proved to be Club No. 12. Cambridge, MA U.S.A. excellent field assistants. The Wildlife Conservation Society ———. 1985. Evolution of ecological segregation in the in Goroka, Eastern highlands, provided outstanding sup- New Guinea montane avifauna. Pages 98–125 in T. port, and I am grateful to them, especially A. Mack, J. Kol, and O. Oneka. Accommodation and logistical support Case and J.M. Diamond [EDS.], Community ecology. were provided by P. and B. Ellis at the Goroka Prep School, Harper and Row, New York, NY U.S.A. and advice and transport were provided by P. Limu of DUMBACHER, J.P., B.M. BEEHLER,T.F.SPANDE, AND H.M. Ramu Sugar, Ltd. K. Yombu and M. Poliaka guided me GARRAFFO. 1992. Homobatracho toxin in the Pi- through the highland grasslands. R. Topiso and R. Palia tohui: chemical defense in birds? Science 258:799–801. allowed access to the Mt. Hagen airstrip. FERGUSON-LEES,J.AND D.A. CHRISTIE. 2001. Raptors of the This expedition was funded by Natural Research, Ltd., world. Oxford University Press, Oxford, U.K. U.K., The Acopian Center for Conservation Learning at FLANNERY, T. 1995. Mammals of New Guinea. Reed Books, Hawk Mountain Sanctuary, U.S.A., and University of Hei- New Holland, Australia. delberg, Germany. Special thanks to R. Tingay, K. Bild- FRITH,C.B. AND B.M. BEEHLER. 1998. The birds of para- stein, and M. Wink for ensuring the success of the project. P. Barnard and J. Simmons helped with logistics, C. Sey- dise: Paradisaeidae. Oxford University Press, Oxford, mour with statistics, K. Aplin with mammal identification, U.K. B. Beehler with bird identification, and he, B. Coates, I. GILLIARD, E.T. AND M. LECROY. 1961. Birds of the Victor Fefelov, P. Dwyer, P. Gregory, S. Haberle, R. Heinsohn and Emanuel and Hindenburg Mountains, New Guinea. J.-M. Thiollay provided data or previous sightings of harri- Bull. Am. Mus. Nat. Hist. 123:1–86. ers. I thank B. Arroyo and D. Scott for comments on an ——— AND ———. 1967. Annotated list of birds of the earlier version of this manuscript. Adelbert Mountains, New Guinea. Bull. Am. Mus. Nat. Hist. 138:53–81. LITERATURE CITED HAMERSTROM,F.1986.Harrier–hawkofthemarshes. Smithsonian Institute Press, Washington, DC U.S.A. ARROYO, B. 1997. Diet of Montagu’s Harrier Circus pygargus HEADS, M. 2002. Regional patterns of biodiversity in New in central Spain: analysis of temporal and geographic Guinea . J Biogeogr. 29:285–294. variation. Ibis 139:664–672. HOOGERWERF, A. 1964. On birds new for New Guinea or BAKER-GABB, D.J. 1986. Ecological release and behaviour- with a larger range than previously known. Bull. Br. al flexibility in marsh harriers on islands. Emu Ornithol. Club 84:94–96. 86:71–81. HOYT, D.F. 1979. Practical methods for estimating the vol- BARNARD, P.E., R.B. MACWHIRTER, R.E. SIMMONS, G.L. HAN- ume and fresh weight of bird eggs. Auk 96:73–77. SEN, AND P.C. SMITH. 1987. Timing of breeding and LEGRA, L.A.T. 2005. Nest-site selection and behavioural seasonal importance of passerine prey to Northern biology of the New Guinea Harpy Eagle Harpyopsis no- Harriers (Circus cyaneus). Can. J. Zool. 65:1942–1950. vaeguineae. Honors thesis, University of Papua New BAVOUX, C., G. BURNELEAU,A.LEROUX, AND P. NICOLAU- Guinea, New Guinea. UILLAUMET G . 1989. Le Busard des Roseaux Circus a. MACK,A.L. AND D.D. WRIGHT. 1996. Notes on occurrence aeruginosus en Charente-Maritime (France). Alauda and feeding of birds at Crater Mountain biological 57:247–262. research station, Papua New Guinea. Emu 96:89–101. BELL, H.L. 1982a. A bird community of lowland rainforest, MACWHIRTER,R.B.AND K.L. BILDSTEIN. 1996. Northern New Guinea 1: composition and density of the avifau- Harrier Circus cyaneus. In A. Poole and F. Gill [EDS.], na. Emu 82:65–74. The Birds of North America No. 210. The Academy of ———. 1982b. A bird community of lowland rainforest, Natural Sciences, Philadelphia, PA and the American New Guinea 3: vertical distribution of the avifauna. Ornithologists’ Union, Washington DC. Emu 82:143–162. MARSDEN, S.J., C.T. SYMES, AND A.L. MACK. 2006. The re- BIRDLIFE INTERNATIONAL. 2004. Threatened birds of the sponse of a New Guinean avifauna to conversion of world. BirdLife International, Cambridge, U.K. forest to small-scale agriculture. Ibis 148:629–640. BROWN,L.H.AND D. AMADON. 1989. Eagles, hawks and MAYR,E.AND E.T. GILLIARD. 1954. Birds of central New falcons of the world. Wellfleet Press, Secausus, NY Guinea; results of the American Museum of Natural U.S.A. History Expedition to New Guinea in 1950 and 1952. CLARKE, R. 1995. The . Hamlyn species Bull. Am. Mus. Nat. Hist. 103:317–374. guides. London, U.K. NIEBOER, E. 1973. Geographical and ecological differenti- COATES, B.J. 1985. Birds in Papua New Guinea. Vols. I and ation in the genus Circus. Ph.D. dissertation, Free Uni- II. Robert Brown, Port Moresby, Papua New Guinea. versity of Amsterdam, Amsterdam, Netherlands. ——— AND W. PECKOVER. 2001. A photographic guide to RAND, A.L. 1942. Results of the Archbold Expeditions the birds of the New Guinea and New Britain. Dove No. 43. Birds of the 1938–39 New Guinea Expedition. Publications, Queensland, Australia. Bull. Am. Mus. Nat. Hist. 79:425–515. 18 SIMMONS VOL. 44, NO.1

SIMMONS, R.E. 2000. Harriers of the world: their behaviour SYMES, C.T. AND S.J. MARSDEN. 2005. Notes on breeding of and ecology. Oxford University Press, Oxford, U.K. Salvadori’s Teal Anas waigiuensis and other birds in ——— AND L.A.T. LEGRA. 2009. Is the Papuan Harrier a Crater Mountain Wildlife Management Area, Papua globally threatened species? Ecology, climate change New Guinea. Bull. Br. Ornithol. Club 125:11–27. threats and first population estimates from Papua New Guinea. Bird Conserv. Int. 19:1–13. Received 12 June 2009; accepted 20 October 2009