Dr Carla du Toit, Professor Anusuya Chinsamy and Associate Professor Susan Cunning of the University of Cape Town (UCT) have discovered the extraordinary sensory capabilities of Hadeda Ibises (Bostrychia hagedash), shedding light on their remarkable range expansion across Southern Africa.
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The study, published in the prestigious Journal of Avian Biology, emphasises the importance of human soil irrigation and ibises’ remote-tactile foraging abilities in driving habitat expansion.
Du Toit, a researcher from UCT’s Biological Sciences Department and FitzPatrick Institute of African Ornithology, led the study, which discovered that Hadeda Ibises have a unique sensory adaptation that allows them to detect vibrations emitted by buried invertebrate prey such as earthworms.
Significantly, this ability is dependent on the moisture content of the soil. As humans irrigate soils in suburban and agricultural areas, creating wetter substrates, ibises take advantage of this environmental change to locate their prey more efficiently, allowing them to expand their range.
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‘The findings of our study underscore the crucial interplay between environmental factors and sensory ecology in shaping the distribution and behaviour of wetland birds,’ says Dr du Toit. ‘Hadeda Ibises serve as a compelling example of how species adapt to anthropogenic modifications of their habitats.’
The ibises’ sixth sense, remote-touch, allows them to detect vibrations from prey items in the substrate, similar to a combination of touch, hearing and echolocation. The study, conducted at the World of Birds sanctuary in Hout Bay, found that ibises have better foraging success in wetter soils where vibrations propagate more effectively.
‘The rapid adaptation of Hadeda Ibises to changes in soil moisture levels underscores their resilience and adaptability,’ notes Dr du Toit. ‘Understanding the sensory requirements of wetland birds is imperative for effective conservation strategies, particularly in the face of ongoing habitat alterations.’
The study not only sheds light on the ecological dynamics of southern Africa, but it also has global implications for the conservation of wetland and shorebird species. The study emphasises the importance of taking into account animals’ sensory ecology in habitat management and conservation efforts by shedding light on the sensory mechanisms that underpin foraging behaviour.
Further analysis of the study’s data indicates that Hadeda Ibises’ range expansion is closely related to human-induced soil irrigation. This phenomenon has not only facilitated the birds’ foraging activities but has also resulted in their spread in suburban and agricultural areas.
The ibises’ characteristic loud calls have become a familiar feature in and around human settlements, marking a notable shift from their historical distribution in eastern regions of South Africa.
‘Human activities have inadvertently paved the way for the expansion of Hadeda Ibises into new territories,’ says Dr du Toit. ‘As we continue to modify landscapes, it’s crucial to consider the ecological implications and potential cascading effects on wildlife.’
The current research focuses on the tactile sensory systems of modern birds on a global scale, with the goal of understanding the function and evolution of these senses and their associated organs.
Collaboration between UCT scientists and researchers at the University of Cambridge (where Du Toit now works) and other institutions is ongoing, spearheaded by a group of women and sparked by the study of a common South African garden bird species.
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Picture: Charl Durand/Unsplash
