Hornbills as Urban Co-Designers
The Oriental Pied Hornbills of Singapore is a charismatic and colorful bird that has made a tremendous comeback from the brink of extinction. Their comeback is due to the intersection of conservation and urban design through a re-introduction program called the Singapore Hornbill Project. The project invited hornbills as co-designers who collaborated with their human neighbors to increase nesting opportunities in the city.
Hornbills are keystone species and conservation icons for the forest habitats they call home. There are 62 species of hornbills across Africa, tropical Asia, Indonesia, and Papua New Guinea. Three species of hornbills are from Singapore: the Rhinoceros Hornbill, the Black Hornbill, and the Oriental Pied Hornbill. The last of these, the Oriental Pied Hornbill, is the only species that can still be found in Singapore.
The Oriental Pied Hornbill is striking and charismatic. You won’t miss one, as these birds can measure a whole meter in length. Their oversized, downward curving beak is referred to as a bill, and it is composed of honeycombed tissue. Females have a yellow-colored knob, or casque, on the bill, and the males have a smaller casque with more black marks. The body of the Oriental Pied Hornbill features a white belly and thighs and contrasting black feathers and neck. Add to this their large eyes accented by distinct white shapes and you have a creature who is just a marvel to look at.
Designing a Hornbill Nest for an Extreme Sacrifice
The most common nest type amongst all birds is cup-shaped nests, made out of natural materials like twigs and mud. About 38% of bird species make their nests this way. Hornbills, however, are secondary cavity nesters, which means they make nests within existing holes in trees. One may assume that creating a cavity nest is less involved than a traditional nest, but that is far from the case.
A female hornbill first looks for a hole in a tall rainforest tree. With her male mate, they use mud, animal droppings, and/or regurgitated food to seal the entrance of the hole while the female is inside. There is a fantastic BBC Video that shows this hole-sealing process. In the video, the pair uses their large bills as tools to pack down and sculpt the mud around the entrance hole. The male hornbill brings back the mud, and the female helps sculpt it around the rim of the entrance hole. Layer by layer, the mud sets and dries, and the finished result is a beautifully sculpted, smoothly camouflaged seal to protect the cavity nest. This sealed cavity is going to protect the female and her nest from predators, flooding, and cavity-nesting competitors. Because she is in the cavity and won’t be flying, the female plucks out her own flight feathers and uses them as a warm lining for the cavity nest. In this nest, she is essentially entrapped and cannot leave, sacrificing her own freedom for this chance at motherhood.
The tiny entrance hole is just large enough for the male hornbill to drop in food he foraged for his mate. This food includes fruits, insects, and lizards, and sometimes even small birds. Interestingly, the act of nest-sealing could also be an evolutionary trait to prevent male fidelity. This is because the father is so busy bringing food to her as she’s trapped in the cavity that he has absolutely no time to be interested in other birds. The mother incubates the chicks for roughly three weeks and only leaves the nest after seven weeks of being sealed inside. The chicks, however, get sealed back inside until they are large and strong enough to break open the sealed hole themselves a few weeks later.
Singapore’s National Identity as a “Garden City”
Southeast Asia is home to biodiversity hotspots of tropical rainforests, mangrove forests, and grasslands. Hornbills are often referred to as the “farmers of the forest” because they disperse the seeds of forest trees. Hornbills especially love figs, which are abundant in South and Southeast Asian forests. Figs provide fuel for hornbills’ large bodies, and hornbills have been observed to participate in fig feasts with up to 50 other hornbill acquaintances.
While nearly half of the land in Singapore is now covered in vegetation, it wasn't always this way. Singapore went though intense deforestation and urbanization throughout the 1800s and 1900s, especially during British Colonial rule. This was devastating for the Oriental-Pied Hornbills. They completely disappeared from Singapore. When Singapore gained its independence in the 1960s, Singapore’s national identity underwent a transformation that, fortunately, led to a series of initiatives that helped the Oriental Pied Hornbill return from local extinction.
Singapore has transformed into a “Garden City” under the vision of Prime Minister Lee Kuan Yew. The National Parks Board (NParks), founded in 1990, has played a significant role in greening efforts, creating a network of urban green spaces and prioritizing wildlife conservation. A tree-planting campaign ensued, marking the beginning of nationwide greening efforts to form the new identity for Singapore. The expansive network of urban green spaces in this small country today is due to NParks, which includes parks, greenways, gardens, and tree-filled streets and neighborhood districts. Public transportation also increased significantly.
In 1994, after 140 years of not being spotted, a pair of wild hornbills was seen in Pulau Ubin, a small
island in northern Singapore. Ever since, this island has become one of the major Hornbill re-establishment areas.
Conservation, private/public partnership, and a changing national attitude toward urban dwellers’ wild neighbors have changed the narrative surrounding co-existence and urban identity with wild animals.
The Singapore Hornbill Project, a Human-Hornbill Collaboration
Launched in 2006 by NParks and the Wildlife Reserves of Singapore, the Singapore Hornbill Project aimed to reintroduce hornbills to urban areas through artificial nest boxes. Artificial nests were introduced in parts of Singapore where hornbills didn’t even previously occupy, such as Bukit Timah, Pulau Ubin, and Singapore Botanic Garden. Alongside the ongoing greening and tree planting efforts across Singapore, these artificial nest boxes allowed hornbill populations to re-establish within just a few years.
These nests, designed to mimic natural tree cavities, provided essential breeding opportunities. Each artificial wooden nest box measures at about 50 cm by 60 cm by 30 cm, with a front opening that mimics a tree hole. The hornbill pair would still engage in their typical design process of finding the cavity and sealing the hole with mud until a tiny sliver remains just large enough for the father hornbill to insert food through for the nesting mother. Infrared video cameras installed inside both artificial nests and natural nests revealed much of what we know today about the intricacies of chick raising after the female is sealed in the cavity. This is the first project in the world to document the breeding ecology of wild hornbills within an artificial nest.
A few initial successes made a big difference. Between December 2008 and April 2009, three artificial nests were used by hornbills, and between December 2009 to April 2010, this number increased to 7. The program established populations in Bukit Timah, Pulau Ubin, and Singapore Botanic Garden within a few years. The species returned in the 2000s through the myriad of human-initiated design interventions, making this the ultimate comeback story at the intersection of conservation and design.
An Urban Comeback
Oriental pied hornbills are now thriving and successfully adapted to Singapore’s urban environment. With an increasing Hornbill population and a public excited about their return from extinction, Oriental Pied Hornbill sightings are becoming common, with higher numbers of birds spotted in built-up areas without canopy or marsh cover. This is especially surprising when one considers hornbill’s historically preferred environment in dense rainforests. Built-up urban areas seem to support the hornbills’ survival by providing safety from predators, as well as food and nest opportunities.
The Oriental Pied Hornbill, a species perceived as an exotic, wild animal, and its presence and adaptation in the city undo the common conception that wildlife is incompatible with cities. This study, along with the success of the Singapore Hornbill Project, underscores the critical need for urban-friendly conservation strategies across rapidly developing cities, and that conservation efforts should focus on maintaining urban green spaces with open vegetation, providing artificial nests, and protecting marshy areas. The return of the Oriental Pied Hornbill to Singapore is a powerful testament to the potential of the intersection of conservation and urban design. Through collaboration between scientists, urban planners, and the general public, a species once thought to be lost has reclaimed its place in the cityscape.
Remaining Critical of Conservation Charisma
The Oriental-Pied Hornbill’s conservation success did raise some critical questions for me: Are less charismatic species receiving the same level of attention and care? What are some unseen consequences of using a beautiful, flagship species for conservation goals? Not every endangered animal is as visually striking or culturally popular as the beloved Oriental Pied Hornbill, and aesthetics and cultural perception can help ensure a species' survival.
When these perceptions and aesthetic values entwine with a national identity or agenda, conservation gets complicated, affecting the allocation of resources. As we celebrate the hornbill’s resurgence, we must also broaden our conservation efforts to protect the full spectrum of urban biodiversity, ensuring a balanced and sustainable future for all species in our cities.
This Upcoming Season on Animals in the Garden City
I’m excited to be sharing diverse urban animal stories with you for the rest of the season. Each story peels back another layer of what it means to live alongside urban animals. And for me, there’s nowhere better to look at all that complexity than Singapore: a place that embraces a gardenesque, biodiverse urban identity, and yet cannot be romanticized as any kind of paradise for animals. The Singaporean animal stories have inspired and disappointed me about the future of urban-wildlife coexistence.
Rebecca Shen a landscape designer, artist, and animal activist. She is inspired by design to advance interspecies justice and imagine more anti-speciesist spaces. Rebecca graduated with a Master in Landscape Architecture at Harvard Graduate School of Design in 2023. There, she completed her design thesis, Sanctuary State: California’s Cowscape in Transition, which envisions the transformation of an 800-acre industrial cattle feedlot into a cow sanctuary in the San Joaquin Valley. Rebecca contributes as an assistant content creator for the show.
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