Research Paper

INTRODUCTION

The Moluccan scrubfowl, a bird species endemic to Indonesia’s central and northern Maluku Islands (Haruku, Buru, Seram, Halmahera, and Obi Island), has been classified as Vulnerable since 1994 by the International Union for Conservation of Nature (IUCN). The overall adult population of Moluccan scrubfowl is currently estimated to be less than 20,000 individuals (BirdLife International 2024). The primary factor considered by IUCN to determine the conservation status of this bird is the projected 30% decline in its population over the next century due to egg exploitation and habitat destruction (Argeloo and Dekker 1996, Dekker et al. 2000, BirdLife International 2016). Another major threat to the Moluccan scrubfowl is predation on chicks in the absence of parental care (Dekker et al. 2000, Heij and Rompas 2011, BirdLife International 2016). The Moluccan scrubfowl exhibit communal nesting behavior along the coast, which, unfortunately, makes their nests easily accessible to egg collectors. On Haruku Island, the collection of Moluccan scrubfowl eggs is based on the traditional belief that the eggs were given by the ancestors of the people of Kailolo Village, who own the land where the birds nest at Tanjung Maleo (Heij et al. 1997, Heij 2001, Heij and Rompas 2011, Saiya and Heij 2017). Therefore, the village government and traditional leaders collaborate to determine the daily egg harvest schedule and set affordable prices to ensure everyone can benefit from bird eggs. The daily harvesting of eggs has resulted in a consistent decrease in the number of eggs collected on Haruku Island. In 1997, a yearly average of 36,000 eggs was harvested, equivalent to 99 daily eggs. However, by 2017, only 21,707 eggs were collected, equivalent to 59 eggs per day (Heij et al. 1997, Heij and Rompas 2011, Simanjuntak et al. 2020).

At Tanjung Maleo, the Moluccan scrubfowl utilize four nesting sites, and egg excavation occurs at each site. Although these sites are near human settlements, the community specifically guards them due to the belief that their ancestors gifted the eggs for utilization. Therefore, adult individuals are not caught for consumption (Heij et al. 1997, Heij 2005, Heij and Rompas 2011, Leimena et al. 2023a). Moluccan scrubfowls engage in nesting activities throughout the night, commencing at dusk. Several parents construct individual nests at a common site along the coast by excavating holes for egg-laying. The holes are then re-sealed and left to incubate naturally via solar heat on the substrate until the chicks hatch (Dekker and Brom 1992, Heij et al. 1997, Dekker et al. 2000, Heij and Rompas 2011, Harris et al. 2014). Egg collectors can quickly identify nesting sites based on the excavated nest holes (Dekker and Brom 1992, Jones 1992, Jones et al. 1995, Heij et al. 1997, Dekker et al. 2000, Heij and Rompas 2011). As a result, it is easy to collect eggs daily and unsustainably. This decrease in the number of eggs laid suggests a reduction in the population size of adult nesting females in Tanjung Maleo. From 1995 to 1997, Haruku Island had an estimated 4200 nesting females (Heij et al. 1997, Heij and Rompas 2011, BirdLife International 2024). Long-term exploitation of Moluccan scrubfowl eggs has been the leading cause of the absence of bird populations and nesting sites on Bacan Island, Ambon Island, and Ternate Island since 1997 (Heij et al. 1997, Heij and Rompas 2011).

Moluccan scrubfowl chicks and other member species from the Megapodiidae (Galliformes) family exhibit a remarkably precocial physical maturity spectrum. As such, they display behavior and morphology similar to mature individuals and do not rely on parental assistance following hatching. These chicks can regulate their body temperature, forage, run, and avoid predators (Winkler and Walters 1983, Jones 1988, Starck and Ricklefs 1998, Dial and Jackson 2011, Scheiber et al. 2017, Chen et al. 2019). Until now, there has been limited research on the behavioral aspects of megapode, including Moluccan scrubfowl chicks. The most thorough studies of megapode breeding behavior have been on Australian brush turkey (Alectura lathami), including dispersal behavior (Goth 2002, Goth and Vogel 2003) and survival (Goth 2001, Goth and Jones 2001, Goth and Vogel 2002, Dial and Jackson 2011). In contrast, the only reports of post-hatching behavior of Moluccan scrubfowl have been obtained through visual observations of the chicks shortly after hatching. Upon hatching, Moluccan scrubfowl chicks burrow from the depths of the sand to reach the substrate surface and immediately move toward the vegetation surrounding the hatching site (Jones 1992, Heij et al. 1997, Heij and Rompas 2011). Chick movements are no longer visually observed as they are masked by vegetation cover and are presumed to remain near the nest site (Heij et al. 1997, Heij and Rompas 2011).

Monitoring chick dispersal is crucial for comprehending habitat use and post-hatching survival. The application of radio-tracking technology on chicks represents the first study to offer a more comprehensive understanding of Moluccan scrubfowls’ post-hatching behavior, dispersal, and habitat use. Our findings provide valuable insights into the dispersal routes of Moluccan scrubfowl chicks, enabling conservation managers to design post-hatching dispersal pathways that enhance chick survival after hatching.

METHODS

We conducted our study on Haruku Island, in Central Maluku, Indonesia (174 km²; Latitude 3.280° - 3.420° South, longitude 128.360° - 128.420° East). In the north, Haruku Island is bordered by Seram Strait and Seram Island, in the south by the Banda Sea, in the east by the Saparua Strait and Saparua Island, and in the west by the Haruku Strait and Ambon Island. Tanjung Maleo is located on the northwest coast of Haruku Island, adjacent to the Kailolo Village settlement, and is accessible by vehicle and pedestrian transport routes. At Tanjung Maleo, four neighboring nesting sites of different sizes are spaced between 40–160 m from the high tide mark. The four nesting sites are labeled as nesting sites number 1, 2, 3, and 4, respectively, with nesting site number one being the largest at 2118 m² and nesting site number three being the smallest at 373 m² (Fig. 1). The substrate at each nesting site is sand. The habitat around the nesting site is mixed forest with a few shrubs at the edge of the nesting site (Heij et al. 1997). It is overgrown by cananga (Cananga odorata), milkwood (Alstonia scholaris), and banca mangosteen (Garcinia bancana; Leimena et al. 2023b). Likewise, the habitat adjacent to Tanjung Maleo is a secondary forest and mixed orchards or “kebun” as locally known, covered by ficus (Ficus benjamina), durian (Durio zibethinus), coconut (Cocos nucifera), lansium (Lansium domesticum), and nutmeg (Myristica fragrans; Leimena et al. 2023b).

Post-hatching behavior

We studied the chicks after they broke through and reached the surface of the nest site. The diameter of the chicks’ exit holes on the substrate surface was measured after the chicks had moved into the vegetation around the nest site. We used a Handycam (Sony DCR-SR220E60GB) to record the chick’s behavior after hatching, including staying, running, walking, flying, and hiding, and the duration of these behaviors. Video cameras were installed in the vegetation around the nesting sites to record their behavior while not interfering with the chicks’ behavior sequence. Moluccan scrubfowl chicks always hatch and emerge from their nest holes between midnight and early morning (Heij et al. 1997, Heij and Rompas 2011). Therefore, the recording started at 3:00 AM and ended at 7:30 AM.

Radio-tracking dispersal, distance, and habitat use

Radio-tracking was employed to investigate the dispersal of Moluccan scrubfowl chicks by monitoring individual position changes. Four chicks were captured from nesting site two after surfacing and securely held using the reverse two-handed grip technique, with the head directed toward the holder to aid with the transmitter attachment (Whitworth et al. 2007). Newly hatched Moluccan scrubfowl chicks typically weigh between 59 g and 92 g (Heij et al. 1997, Heij and Rompas 2011). As such, to avoid interfering with the birds, the weight of the transmitter should not surpass 10% of the chick’s body weight (Fair et al. 2010). The transmitter model used was the Sirtrack V8009 (151 MHz), weighing 1.90 g (2.1–3.2% of hatchling weight) and affixed to the wingbase using a Loctite cyanoacrylate adhesive. The birds were tracked daily on foot from 6:00 AM until 6:00 AM the following day using the six-arm Yagi antenna and Biotrack Sikka VSR 04. All four chicks were tracked at the same time. The coordinates of each chick were determined using a Garmin 64S GPS set. Radio tracking took 40 non-consecutive days during the transmitter’s active period. ArcGIS 10.3 software was used to plot the coordinates of each chick on a map of the study site. Radio-tracking data were used to analyze the movement, distance, and direction of dispersal of chicks from their nesting site.

Habitat use by chicks during dispersal was categorized by land cover type. We analyzed the land cover of Haruku Island using ESRI’s ArcMap version 10.3 software, based on the 2016 land cover map of Haruku Island, 2016 Google Earth image data, 2017 Indonesian landform map of Haruku Island at 1:50,000 scale, and 2009 5 TM Landsat images (color composite band 2 - 4) at 30 m spatial resolution. Land cover types were classified using the National Standard for Classification of Indonesian Land Cover (National Standardization Agency of the Republic of Indonesia 2010).

RESULTS

Post-hatching behavior

Our study observed and recorded 263 Moluccan scrubfowl chicks. We observed that the chicks’ emergence at the surface occurred between 3:50 AM and 7:00 AM, with most emergence occurring around 4:00 AM. Successfully emerged chicks left holes on the sand surface with a 15–18 cm diameter. Such exit holes were visible in the morning if no other activity was around the nesting ground (Fig. 2).

After reaching the sand surface, the chick remained stationary for 0.5–2.0 minutes (1.2 ± 0.7, n = 263) before running or flying toward nearby vegetation at distances ranging from 0.10 to 41.00 meters. The movement of the chick toward the nearest vegetation occurred in less than one minute, which consisted of running (0.6 ± 0.2, n = 124) and flying (0.6 ± 0.2, n = 139). Once the chicks entered the surrounding vegetation, the radio-tracking results showed that they stayed in the vicinity of the nest site for approximately 1.0–3.0 minutes (2.1 ± 0.7, n = 263) before moving away from the nest site within the next 3.0 - 15.0 minutes (8.4 ± 0.2, n = 263; Table 1, Fig. 3).

Dispersal direction

One of the four radio-tracked chicks perished on the eighth day, while the remaining three survived until the end of the study period. Body remains were discovered when tracking the transmitter in the deceased chick, leading to suspicion that an unidentified predator was responsible for its demise. The results showed that Moluccan scrubfowl chicks started to move away from the nest site after hatching and dispersal away from the nest site rapidly in the first 4 hours, reaching an average distance of 260 ± 20 m. During the next 4-hour interval until the end of the first day, the chicks traveled an average distance of 22.5 m until they reached a distance of 350 ± 40 m from the nesting site at the end of the first day. From the second day to the end of the second week, the chicks moved an average of 37 m per day, eventually reaching 480 m from their nesting site. The distance traveled by the chicks then increased to 43 m per day from the third to the fourth week, reaching 1030 m. In the fifth week, the distance traveled by the chicks increased by 90 m compared to the fourth week, but in the sixth week, they traveled 60 m in the opposite direction. Radio-tracking data showed that Moluccan scrubfowl chick’s maximum distance from their nesting site at Tanjung Maleo ranges between 1060 m and 1120 m (Table 2B). Based on the position of the nesting site on the coast of Tanjung Maleo, the dispersal direction of chicks was only possible inland, with an average orientation of 117 degrees.

Early in their dispersal, Moluccan scrubfowl chicks used mixed forest habitats around their nesting sites and moved to dryland forests or mixed dry agriculture habitats. From the second to the sixth week, the remaining three chicks actively foraging in both habitat types (Fig. 4). These findings suggest that Maluku scrubfowl chicks only utilize the vegetation surrounding their nesting habitat for a brief duration after hatching and rapidly move away from it.

DISCUSSION

Post-hatching behavior and dispersal

Through video and GPS tracking, we describe in detail the process of hatching of Moluccan scrubfowl and their behavior, including dispersion, distance, and habitat use. Shortly after hatching, Moluccan scrubfowl chicks move directly into the nearest vegetation. Previous studies at Tanjung Maleo by Heij et al. (1997) and Heij and Rompas (2011) reported visual observations of the same behavior of Moluccan scrubfowl chicks moving directly into the nearest vegetation after hatching. The use of radio-tracking provided more accurate information about the movement of the chicks, allowing the study to overcome the limitations of visual observation when the hatchling entered the vegetation cover. Behavioral studies of another megapode, the Australian brush turkey (Alectura lathami) chicks, have also shown their movement to nearby vegetation soon after hatching (Goth and Evans 2005). The movement of chicks to nearby vegetation soon after hatching is likely to avoid open areas of nesting sites. Previous studies have shown that predation of Moluccan scrubfowl chicks is common upon emergence from the nest hole by snakes, birds, or cats (Heij et al. 1997, Heij and Rompas 2011). For the first time, we describe the speed at which chicks moved away from the coast into dryland forest and mixed dry agriculture habitats, moving on average 114.52 meters per day, and that within 40 days, they had moved into dryland forest and mixed dry agriculture habitat and up to 1060–1120 m away from the nesting site. The average distance traveled by Moluccan scrubfowl chicks after hatching is greater than that of Australian bush turkeys (Alectura lathami), which only travel between 100–150 m for shelter and foraging during the first few weeks after hatching (Goth and Jones 2001). From the position of the nesting site at Tanjung Maleo, the dispersal direction of Moluccan scrubfowl chicks is toward dryland forest areas to the southeast of the nesting site. With age, chicks then move into mixed dry agriculture habitats. Research on the Australian bush turkey chicks suggests that the availability of food and shelter in densely vegetated areas strongly influences chick habitat choice (Goth and Evans 2005). Therefore, the need for food and shelter may be the primary driver for moving Moluccan scrubfowl into dryland forests or mixed dry agricultural habitats.

Dispersal studies in birds have shown that surface foragers are highly mobile and have long dispersal distances as they move through different habitat types in search of food, despite having fewer flight attempts than flying birds (Claramunt et al. 2022, Naka et al. 2022, Chu and Claramunt 2023). Some studies have even shown that even in productive tropical forests, ground foraging species have higher mobility rates than species that forage on understory vegetation (Claramunt et al. 2022, Naka et al. 2022, Chu and Claramunt 2023). The characteristics of surface foragers match the behavior of Moluccan scrubfowl, which are more active on the ground when foraging or nesting (Jones and Birks 1992, Harris et al. 2014), so they may disperse long distances after hatching. Differences in habitat productivity between the Moluccan scrubfowl and the Australian bush turkey may explain the differences in dispersal distance between the two species. In avifauna, the limited distribution of habitat resources affects dispersal distances, with individual birds dispersing further in unproductive foraging habitats than in productive ones (Sutherland et al. 2000, Swift et al. 2021, Claramunt et al. 2022, Naka et al. 2022, Chu and Claramunt 2023). Thus, the results of this study suggest that the Moluccan scrubfowl habitat on Haruku Island is relatively unproductive, causing newly hatched chicks to disperse further from their nesting sites as they explore their habitat. A further implication of the long dispersal distances of Moluccan scrubfowl relates to their population size on Haruku Island. Moluccan scrubfowl’s long dispersal distances indicate that their population size is small. When bird populations are large and habitats are productive, individual birds do not need to disperse long distances to find resources they can utilize (Paradis et al. 1998, Claramunt 2021, Chu and Claramunt 2023). Due to visual limitations in detecting the direction of movement of hatchlings, studies of the dispersal of megapode chicks are relatively rare. However, based on visual observations during early hatching, megapode chicks always move toward vegetation close to their nesting sites, as shown by the dispersal of Philippine scrubfowl (Megapodius cumingii) chicks on Palawan Island in the Philippines (Paguntalan et al. 2021) or Australian bush turkey chicks in Australia (Goth and Jones 2001). Compared to this study, visual observation could not detect the dispersal radius of Philippine scrubfowl chicks on Palawan Island in the Philippines (Paguntalan et al. 2021).

From the position of the nesting site at Tanjung Maleo, the dispersal direction of Moluccan scrubfowl chicks is toward dryland forest areas to the southeast of the nesting site. With age, chicks then move into mixed dry agriculture habitats. Research on the Australian bush turkey chicks suggests that the availability of food and shelter in densely vegetated areas strongly influences chick habitat choice (Goth and Evans 2005). Therefore, food and shelter may be the primary drivers for Moluccan scrubfowl to move into dryland forests or mixed dry agricultural habitats. Previous research in 2022 revealed that most of the Moluccan scrubfowl population residing on Haruku Island was active in both habitat types near their nesting site at Tanjung Maleo (Leimena et al. 2022a, Leimena et al. 2023b). It is clear from several studies of megapods that most birds are active in habitats close to their nesting sites. This behavior is demonstrated by the malleefowl (Leipoa ocellata) in Australia (Booth 1987), the Sula scrubfowl (Megapodius bernsteinii) in the Banggai Islands, Indonesia (Indrawan et al. 1998), the Maleo (Macrocephalon maleo) on Sulawesi Island (Tasirin et al. 2021, Karim et al. 2023), and the Philippine scrubfowl on Manumpitaeng Island, North Sulawesi, Indonesia (Bashari et al. 2017), or on Palawan Island, Philippines (Paguntalan et al. 2021). Compared to this study, which used a radio-telemetry approach, most studies of megapodes have relied on visual observations, which have yet to confirm the dispersal distances and habitat types used by the birds. In terms of habitat use, this study identified the habitat type used by Moluccan scrubfowl on Haruku Island as dryland forest or mixed dry agriculture habitats, adding to the list of habitat types used by individual megapodes in their natural habitat. Indeed, many studies have shown that the habitat types around nesting sites and the daily habitats of megapode groups are diverse. The habitat around the nesting site of the Philippine scrubfowl in Palawan Island, Philippines, is coastal forest and lowland tropical forest (Paguntalan et al. 2021) or Maleo habitat in Sulawesi Island varies from coastal forest, tropical rainforest (Tasirin et al. 2021, Bashari et al. 2022, Kumaji et al. 2024), lowland primary or secondary forest (Jones et al. 1995, Bashari et al. 2022), and plantation (Jones et al. 1995). Similarly, several studies on the habitat of Moluccan scrubfowl on Halmahera and several islands in Central Maluku show that their habitat varies from secondary forest, open coastal forest, and lowland forest to tropical rainforest above 750 meters above sea level (Dekker et al. 1995, Heij et al. 1997, Heij 2001, Heij and Rompas 2011, BirdLife International 2024).

Conservation Aspects

For Moluccan scrubfowl chicks, dispersal behavior will determine their survival due to the proximity of nesting sites to human settlements. Human settlements near nesting sites can reduce the vegetation cover around nesting sites and the size of nesting sites through the expansion of residential areas. The lack of vegetation cover around nesting sites will ultimately affect the dispersal routes of chicks and the availability of their first post-hatching shelter. Therefore, preventing and mitigating damage to vegetation is a crucial consideration in conserving the Moluccan scrubfowl. Based on the findings of this study, conservation approaches for this species should focus on conserving vegetation around nesting sites in Tanjung Maleo and vegetation that serves as dispersal routes for chicks. Maintaining the vegetation around the Moluccan scrubfowl nesting site in Tanjung Maleo is essential as it is very close to the residential area, making it vulnerable to conversion or destruction. Vegetation conversion and destruction can be prevented by the spatial arrangement and management of the nesting area and by sanctioning the perpetrators of destruction. Based on the existing condition of the vegetation cover, the area of vegetation cover around bird nesting sites that need to be conserved is 98.038 m². This vegetation cover includes the vegetation around the bird nesting site in Tanjung Maleo and the vegetation cover that connects the nesting site with dry forest and mixed dry agricultural habitats near the bird nesting site. In the context of this study, the primary function of vegetation cover around bird nesting sites is as a temporary shelter for newly hatched chicks and as a dispersal corridor for chicks as they move away. The vegetation cover that needs to be maintained as a dispersal corridor for chicks is the vegetation cover in the southeast of Tanjung Maleo, which connects the nesting site with the nearby dry forest and mixed dry agricultural habitat. Visual observations of Maleo movements in Sulawesi during and after nesting have shown the importance of green corridors for Maleo to move from open areas into the forest interior to avoid predators (Tasirin et al. 2021).

Therefore, based on the findings of this study, we recommend several conservation actions for Moluccan scrubfowl on Haruku Island. The main conservation priorities are to conserve habitat around nesting sites, conserve and secure dispersal routes or corridors for chicks from nesting sites to adjacent forest areas, and conserve forest around nesting sites in Tanjung Maleo. These recommendations need to be reinforced in the form of special regulations issued by the local government or village government, as well as the establishment of a monitoring unit to oversee the implementation of the regulation. In comparison, Maleo conservation in Sulawesi also focuses on the bird’s nesting sites and surrounding habitats (MacKinnon 1981, Baker and Butchart 2000, Tasirin et al. 2021, Bashari et al. 2022, Andriwibowo and Maarif 2023, Summers et al. 2023). Studies on other megapodes have also demonstrated the importance of nesting sites and their surrounding habitats for megapode conservation, such as in the Philippine scrubfowl (Megapodius cumingii; Paguntalan et al. 2021), Micronesian megapodes in the Mariana Islands in the Pacific (Amidon et al. 2011, unpublished report), Malleefowl (Leipoa ocelata) in southern Australia (Benshemesh 2007), and Polynesian megapodes (Megapodius pritchardii) in Tonga (Goth and Vogel 1995, Lloyd et al. 2011). The success of Maleo conservation in Sulawesi has also been determined by the implementation of patrols by forest rangers together with local communities to prevent poaching, illegal egg collection, habitat destruction, and strict law enforcement against violators (Baker and Butchart 2000, Tasirin et al. 2021, Kumaji et al. 2024). Conservation of forest areas adjacent to bird nesting sites is also a conservation priority due to the threat of land conversion (Tasirin et al. 2021, Bashari et al. 2022, Summers et al. 2023, Kumaji et al. 2024). The provision of Maleo movement corridors from nesting sites to inland forests is also recommended for Maleo conservation efforts in Sulawesi (Baker and Butchart 2000, Bashari et al. 2020, Summers et al. 2023). In this study, dispersal corridors were intended to accommodate the movement of chicks away from their nesting sites after hatching. Given the experience of Maleo conservation in Sulawesi, where egg collection from nesting sites is prohibited (Tasirin et al. 2021, Bashari et al. 2022, Summers et al. 2023), the conservation of vegetation around nesting sites and dispersal corridors must be done in conjunction with efforts to limit the number of eggs that the community can take. The study of community perceptions of conservation around bird nesting sites in Tanjung Maleo also recommends limiting the number of Moluccan scrubfowl eggs that can be taken to meet the economic interests of the community concerning traditional beliefs while taking into account the sustainability of bird populations (Leimena et al. 2022b). Another recommendation to increase the effectiveness of Moluccan scrubfowl conservation is to raise public awareness and government institutions toward the conservation of the Moluccan scrubfowl and the impact of egg collection and habitat destruction on its population on Haruku Island. The status of the Moluccan scrubfowl as an endemic bird species, the uniqueness of its reproductive behavior, and the existence of the Tanjung Maleo area as one of the main nesting sites in Maluku are added values that can be used to promote public awareness of the Moluccan scrubfowl.

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