The Asian openbill (Anastomus oscitans), a large stork species, has recently become a more frequent visitor to Singapore. Previously a rare sight in the region, these birds are now being drawn from their usual habitats in Thailand, Cambodia, India, and Sri Lanka due to food scarcity. These birds are easily recognisable by the distinctive gap in their beaks and their tendency to gather in large flocks. The first large flocks in Singapore were observed over a decade ago in 2013, but this year, the numbers have surged, with hundreds now spotted in the southern and eastern parts of the island, near Punggol and Changi. While bird watchers may find this fascinating, the growing presence of the Asian openbill near airports raises concerns about aviation safety. With birds that can reach heights of 80 cm and wingspans exceeding one meter, the risk of a bird strike is a serious consideration for aviation authorities.
The Migratory Patterns of the Asian Openbill
Asian openbills are known for their unpredictable migratory patterns, with some years seeing large numbers of birds in Singapore and others seeing none. As migratory birds, their movements are influenced by seasonal monsoons, food availability, and the conditions of their typical habitats. When their usual feeding grounds suffer from droughts or flooding these storks often turn to alternative locations, including Singapore’s wetlands, reservoirs, and airports. The island’s abundance of green spaces and water bodies provides an ideal stopover, offering a temporary refuge and a reliable source of food for these birds, who primarily feed on snails and small aquatic creatures. As climate patterns continue to shift, tracking their arrival has become increasingly difficult, adding an element of unpredictability for airport authorities.
A Snail Feast: The Openbill’s Meal of Choice
The Asian openbill’s food source of choice in Singapore? Snails. These nomadic hunters have found Singapore’s snail population to be an abundant resource. Interestingly, Singapore is home to an introduced species of African snail, which is largely ignored by native birds. This gives the openbills a competitive advantage, as they feast on these snails with little to no competition from other local wildlife. Singapore has become an all-you-can-eat snail buffet for these birds.
What Can Airports Do?
With the presence of Asian openbills increasing in Singapore, airports must take proactive measures to manage the potential risk of bird strikes, even as it remains uncertain whether their numbers will continue to rise, if some will stay while others leave, or if even larger numbers may return in the coming years.
Regular Surveys: Monitoring bird movements around airports on a regular basis helps predict periods of abnormalities. Surveys should be conducted both within the airport and in the surrounding areas. It is important to collaborate with various stakeholders to ensure comprehensive data collection and effective monitoring.
Hazing Techniques: Active deterrents, both visual and auditory, are effective at keeping migratory birds away from flight paths. Unlike resident birds, which can become accustomed to hazing methods, migratory species like the Asian openbill are more easily startled by new and sudden stimuli. Simple measures, such as waving bright red flags, have proven highly effective in dispersing the storks. From our experience with the openbills in Singapore, they are not deterred by sounds as much as the visual deterrents. However, as with any deterrent, habituation remains a concern—how long will this method continue to work?
Habitat Modification: The Asian openbill thrives in wet, grassy areas. Reducing water sources and preventing ponding in and around airports can limit food availability and discourage large flocks from settling nearby. The start of the year in Singapore is quite wet and influenced by monsoons, leading to increased water pooling and a greater abundance of snails and other food sources. One technique to reduce the snail population involves spreading calcium oxide (quicklime). This substance reacts with water to create an alkaline environment that is lethal to snails. While effective, the use of quicklime must be carefully managed to avoid harming other organisms or altering the soil’s pH to undesirable levels.
Stakeholder Management: In a small, densely populated country like Singapore, managing large flocks of migratory birds near airports is an especially difficult challenge. It’s not just the limited land space that makes bird dispersal tricky—it’s also the sheer number of stakeholders involved and the close proximity of multiple airports. Unlike in rural areas, where birds can be safely driven to distant locations, improper dispersal efforts in Singapore risk simply shifting the problem from one airport to another. Without careful coordination between airport authorities, landowners, and government agencies, birds can end up flying between sites, adding to the hazard rather than resolving it. This makes our work particularly challenging, requiring constant communication and strategic planning to ensure dispersal efforts are effective and sustainable.
Striking a Balance
The Asian openbill’s growing presence in Singapore is an exciting addition to the nation’s wildlife, but it also presents a challenge we cannot ignore. Their large size, flocking behaviour, and feeding habits pose a real aviation safety risk, especially during peak migration seasons. Managing this goes further than just wildlife or aviation—it’s about bringing people together to find solutions that work for both. By collaborating with each other, closely monitoring openbill movements, and implementing thoughtful strategies, we can ensure that Singapore remains a safe place for air travel while embracing the richness of its natural heritage.
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