Fatal attraction: How international trade is driving African hornbills towards extinction

Massive birds whose loud wingbeats and rollicking cries resound through tropical rainforests, African hornbills were a common sight in my experience working in Gabon, Central Africa, 30 years ago. Highly gregarious, African hornbills are impossible to miss as they fly around in large, boisterous flocks in search of fruiting trees, and I had the pleasure of seeing them often during that time. Ten years later, I returned to the African rainforests, this time in Ghana. But something was missing, I soon realized… the hornbills I had consistently encountered previously were nowhere to be seen.

Where had all the hornbills gone? Colleagues at the University of Ghana and I decided to investigate. Our research revealed that most hornbill species in Ghana had declined and disappeared in most of their former ranges due to persecution and habitat destruction. As the wild mammals favored by hunters dwindled, hornbills were increasingly targeted as an alternative source of meat and income. What we didn't fully appreciate then is how the dire situation of forest hornbills we found in Ghana reflects a wider pattern across the continent, which has continued to worsen with rapidly expanding human activities, shrinking habitat, and climate change.

Since then, threats to African hornbills have grown even more serious, as subsequent research has demonstrated that demand for African hornbills has been increasing in international trade. In Cameroon, for example, reports of foreign buyers looking to purchase large numbers of hornbill heads have meant that local hunters who had otherwise left hornbills alone could make easy money targeting hornbills, resulting in declines and extirpations. Recently, I joined colleagues from across Africa, Eurasia, and the U.S. to investigate the hornbill trade in an effort spearheaded by scientists at the United States Fish & Wildlife Service (USFWS).

Globally, hornbill taxa are nearly equally divided between Africa and Asia. Asian hornbills have been traded for centuries, with accelerating trade driving some species to near extinction, notably the critically endangered Helmeted Hornbill. The Convention on International Trade in Endangered Species (CITES) offers protection through regulating wildlife imports and exports. Awareness of the perils posed by wildlife trade led most Asian hornbills to receive CITES protection in 1992, but international trade in African hornbills has remained largely unregulated and poorly documented.

Might CITES protection of some species in decline displace demand onto similar, unprotected species? Here, we asked whether protecting Asian but not African hornbills under CITES has enabled the accelerated trade in African hornbills to threaten their continued survival. To explore this question, we analyzed USFWS data on all hornbill trade from 1999 to 2024 through their Law Enforcement Management Information System (LEMIS) database. We also analyzed hornbill trade data from sources including online platforms and databases such as from Trade in Wild Species (TRAFFIC). Our study, published in the journal Biological Conservation, investigates how increasing international wildlife trade threatens biodiversity globally, and African hornbills specifically.

Our findings show that African species account for nearly 95% of traded hornbills and that trade in African hornbills has increased significantly over time, while trade in Asian hornbills has remained constant under CITES management. Over our 25-year study period, Cameroon has been the biggest supplier of African hornbills to the US, accounting for ~25% of traded hornbills overall, followed by Tanzania (~17%), Senegal (~10%), and Guinea (~9%).

Until 2004, hornbills from East Africa dominated the US trade; subsequently, until 2020, West Africa was the most common source of African hornbills to the US. But since 2021, Cameroon and the Democratic Republic of Congo in Central Africa have shipped more than two-thirds (~67%) of all African hornbills to the US.

Almost half (~45%) of all hornbills shipped to the US were live birds, almost certainly captured from the wild, as hornbills are notoriously difficult to breed in captivity. By contrast, most trade in Africa involves killing birds, often to decapitate them and sell their heads. A recent seizure in Nigeria of 128 hornbill heads being shipped for trade, including Black-casqued Hornbills (Ceratogymna atrata) and White-thighed Hornbills (Bycanistes albotibialis), highlights the dangers posed to these species' survival by escalating market demand.

Demand for African hornbills in trade has caused population declines throughout their ranges. Every genus of African hornbill is traded internationally, but ~86% of trade comprises four genera: Ceratogymna, Bycanistes, Tockus, and Lophoceros. Levels of US trade in the African hornbill genera Ceratogymna and Bycanistes alone likely exceed global trade in all Asian hornbills prior to their CITES protection.

For the two African hornbill species designated as vulnerable to global extinction on the IUCN Red List of Threatened Species, the Yellow-casqued Hornbill (Ceratogymna elata) and Brown-cheeked Hornbill (Bycanistes cylindricus), ongoing trade poses an existential threat. The Yellow-casqued Hornbill provides a salient case in point. This species survives in Ghana in a single protected area and has not been seen alive in Togo for 37 years; yet this year, a freshly killed individual of this species was offered for sale in Togo in what is often called the world's largest voodoo market.

Hornbills are amazing birds and important seed dispersers, playing key roles in shaping forests and woodlands, and are naturally long-lived, with slow reproductive rates. During the breeding season, female hornbills seal themselves into nest cavities for up to 160 days to protect their eggs, chicks, and themselves from predators. Because of this unique nesting strategy, females rely on males more than in any other bird species. However, almost three-quarters (~73%) of African hornbills identified in online trade in our study were males, underlining the cascading effects of their vulnerability to the ultimate predators—people.

As people are driving this problem, people also have the capacity to solve it. We therefore urgently recommend that African hornbills receive protection from uncontrolled international trade through listing them on CITES Appendix II at the next Conference of the Parties. Thus, protecting African hornbills would provide a lifeline to the wild forests and nature on which so many Africans depend, and the unique, magnificent beauty that draws people to Africa from around the world.

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about Science X Dialog and how to participate.

Nico Arcilla is a member of the IUCN Species Survival Commission Hornbill Specialist Group and director of the International Bird Conservation Partnership, whose mission is to foster and support research, outreach, and partnerships to advance the conservation of birds worldwide. An affiliate fellow at the University of Nebraska-Lincoln, she earned her PhD in wildlife biology from the University of Georgia, USA.