Scientists have discovered that the hooting calls of tawny owls cause robins to decrease their food intake during nighttime stops on their autumn migration. This behavioral adaptation highlights how the presence of nocturnal predators influences the survival strategies of these small birds.
The study, conducted by researchers from Lund University in Sweden, focused on young robins making their first southward migration. During this journey, the birds make frequent stopovers to rest and replenish energy. However, these stops expose them to potential threats from predators like the tawny owl.
Lead researcher Professor Susanne Åkesson explained that the robins not only detect nearby predators but also adjust their behavior depending on the specific predator calls they hear. In controlled experiments, young robins were exposed to calls from two different raptor species: the nocturnal tawny owl and the daytime sparrowhawk.
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The findings, published in the Journal of Animal Ecology, showed a clear distinction. While the sparrowhawk calls had little effect, the tawny owl’s hooting triggered a strong response—robins became more cautious, reduced night-time activity, and significantly decreased their feeding. This led to slower fat accumulation and a decline in physical condition.
Professor Åkesson noted, “The birds face a clear trade-off: they must balance the risk of predation with the need to build up energy reserves for migration.” Because feeding less forced the robins to extend their stopovers, they faced increased risks of arriving late at wintering sites, where competition for territory is fierce. Late arrival can negatively affect both survival and breeding success.
The research underscores the importance of providing safe and calm environments at stopover sites. “By understanding how migratory birds respond to different threats, we can improve habitat planning to support their survival during these critical journeys,” Professor Åkesson added.