Studying Maleos in the Zoo and the Field

Maleo Photo
The maleo is an unmistakable bird, with its distinctive bony, dark casque, yellow facial skin, and red-orange beak.
Julie Larsen Maher ©WCS

Found only on the Indonesian island of Sulawesi, the maleo is an endangered and wonderfully unique bird. About the size of a chicken, it has a blue-gray back, a pink breast, yellow facial skin, a red-orange beak, and a dark grey helmet or “casque.” But what makes maleos truly unique are their nesting habits. Females lay one enormous egg—five times larger than a chicken’s—and bury it in sun-baked sands of beaches or volcanically heated soils on communal nesting grounds. After depositing her egg, the mother bird moves on. When the chick hatches and emerges from underground, it can fend for itself. Immediately, it runs or flies to the nearest forest. As a result, protection of the corridors between the nesting grounds and the inland forests is critical.

Much of what we know about this rare bird’s nesting needs comes from work done by WCS-Indonesia field staff and the Bronx Zoo Bird Department. The zoo is the only home for maleos outside Indonesia, and its staff has nurtured many maleo eggs in its brooder room. Several chicks have hatched under the careful watch of zookeepers and curators.


Sulawesi is an exceptionally important area for wildlife conservation. Of the island’s 233 species of birds, 36 percent are endemic, including the maleo. But despite the maleo’s importance to science and to the island’s cultural heritage, its future is uncertain. In 2006, the global population was estimated at fewer than 5,000 birds. Its nesting grounds are highly threatened by poaching for the enormous eggs, as well as predation by dogs and pigs. Almost all of the beaches in northern Sulawesi where maleos are known to nest lie outside of protected areas. In addition, the habitats between the beaches and natural forests are subject to clearance for agriculture. When the distance between the nesting ground and the forest becomes too great, birds simply do not return to the nesting grounds to lay. Of the 36 known nesting sites in North Sulawesi, the birds have abandoned half. In fact, the number of maleo pairs visiting nesting grounds has declined by 90 percent since the 1950s.

What WCS is Doing

WCS-Indonesia has managed three inland hot-spring nesting grounds since 2001 at Tambun and Muara Pusian in the east of Bogani-Nani Wartabone National Park and Hugayono in the west. Through our educational outreach programs, many nearby villagers have changed their attitude toward the birds and now support their protection. We employ local guardians to protect these nesting sites and to educate visitors. We also work as conservation partners with the staff of Bogani-Nani Wartabone National Park. With their help, more than 4,000 maleo chicks have successfully hatched in the wild over the course of six years.

The protected nesting sites now attract foreign eco-tourists. Visitors can take in the hot-springs or beautiful beaches, watch the adult birds digging the nest pits and—with a little luck—see new chicks digging themselves from the ground once they hatch.

In 2009, the WCS-Indonesia Program and the Bronx Zoo Bird Department helped a local NGO, Pelestarian Alam Liar dan Satwa, buy a private beach for the birds on one of their most active nesting grounds in North Sulawesi. Located at Binerean Cape, the beach is also an important nesting ground for green, leatherback, and olive ridley turtles. WCS staff members are working to safeguard the turtle nests, which have produced some 500 hatchlings this season. In addition to birds and turtles, the beach supports a coconut farm that produces more than 10,000 coconuts per year. Funds from the harvest will be used to pay local guards to protect the beach’s wildlife. We hope these efforts will soon culminate with the successful hatching of the 5,000th chick.

The WCS-Indonesia Program and the Bronx Zoo Bird Department—whose staff has visited Sulawesi to study the maleo’s beach and inland nesting grounds—continue to share information on the birds. Before the groundbreaking work of these two teams, little was known about the necessary temperatures for proper incubation. The inland and beach nesting grounds have striking differences, as the heat source for incubation inland comes from volcanic activity below, while the beach sites get their the heat from the sun above. By comparing the two environment types, Bronx Zoo and WCS-Indonesia field staff will be able to enhance maleo protection and habitat management and determine whether the populations in each are distinct. Once we discover the answer, we’ll know whether we can consider transporting eggs to nesting sites that the maleo has abandoned. These studies have also helped improve maleo management and enhance egg-hatching success at the Bronx Zoo.

From the Newsroom

A Bird Like No Other: Raising MaleosMarch 19, 2013

After carefully recreating the conditions needed for incubation, WCS ornithologists at the Bronx Zoo helped a maleo family hatch three rare chicks. The zoo is the only home for maleos outside Indonesia, and the staff’s insights into this rare bird’s nesting needs will improve conservation efforts on behalf of its wild cousins.

Rare Birds Get Private BeachMay 13, 2009

WCS helps buy an exclusive stretch of sand on the Indonesian island of Sulawesi, where the endangered maleo lays its giant eggs. The beach is also a haven for sea turtles.

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