How the Eurasian Scops Owl Chooses Prey While Raising Its Chicks
- 演化之聲
- Apr 9
- 3 min read
For a long time, the Eurasian Scops Owl (Otus scops) has generally been known as an insect-eating owl during the breeding season, with a particular reliance on Orthoptera such as bush-crickets and grasshoppers. However, the finer details of its chick provisioning behavior have remained difficult to document. In this study, conducted in a peri-urban Mediterranean forest in northeastern Spain, researchers used a high-resolution night-vision camera to continuously record the prey deliveries of a breeding pair during the chick-rearing period. Monitoring lasted for 11 nights, totaling approximately 90 hours. The study itself began after an accident: the original natural nest collapsed, causing the death of some nestlings, while the surviving chicks were transferred into a newly installed artificial nest box. The researchers then took advantage of this opportunity to set up a night-vision camera outside the nest box and document parental provisioning behavior in detail.
Consistent with previous knowledge, Orthoptera accounted for about 64.6% of all prey delivered by the adults and represented the dominant food source. Among these, Uromenus rugosicollis was one of the most frequently recorded species, together with Tettigonia viridissima, Meconema thalassinum, Barbitistes fischeri, and a smaller number of other large orthopterans. In addition to Orthoptera, the owls also captured stick insects, Lepidoptera, mantises, and spiders, and they occasionally brought back geckos and rodents. Although vertebrates represented only about 1.8% of all provisioning events, rodents alone accounted for approximately 20.3% of the total biomass, indicating that the Eurasian Scops Owl supplements its chick diet with a small number of energetically valuable vertebrate prey.
Among orthopteran prey, however, not all species contributed equally. The most frequently captured prey were not necessarily the most energetically profitable. For example, Tettigonia viridissima was not the most abundant prey item numerically, yet it provided the highest average biomass per individual. This suggests that the Eurasian Scops Owl combines two complementary foraging strategies during chick provisioning. On the one hand, it repeatedly captures smaller, more readily available insects to maintain a steady food supply. On the other hand, it also targets larger and more profitable prey to increase the overall efficiency of chick provisioning. This pattern is also reflected in a marked bias toward female orthopterans, which made up about 65.6% of the identified orthopteran prey, compared with 34.4% for males. Because females in many orthopteran species are larger than males, they provide a greater energetic return, whereas the more conspicuous calling males do not appear to be the principal prey target.
The study also documented a behavior that has rarely been described clearly before. Before delivering female bush-crickets to the nest, the adults often removed the ovipositor at the tip of the abdomen. This structure is hard, sharp, and poorly digestible, and swallowing it could increase the risk of injury for immature nestlings.
The timing of provisioning was also highly structured. Nocturnal chick-feeding activity showed a bimodal pattern. The first peak occurred at around 22:00 h, while the second peak appeared shortly before dawn, around 05:00 h. This rhythm likely reflects a combination of prey activity patterns, light conditions, and the energetic efficiency of the parents, allowing them to concentrate foraging effort at the times when hunting is most worthwhile.
When brood size increased, the number of prey items delivered per night and the total biomass brought to the nest did not increase significantly. This may indicate that parental provisioning capacity has an upper limit, so even if chick demand rises, the adults may not be able to proportionally increase prey delivery. It is also possible that food resources were relatively abundant, such that the original provisioning level was already close to sufficient. In addition, prey brought into the nest did not always correspond directly to prey immediately consumed by the chicks. Some rodent prey items, for instance, were not eaten right away and sometimes remained in the nest, perhaps functioning as temporarily stored food that could later be consumed either by the nestlings or by the adults themselves.
For the parent owls, prey delivery during chick rearing appears to involve several overlapping considerations: selecting prey that are larger and more profitable, processing food in ways that reduce the risk of injury to nestlings, and concentrating foraging activity during periods when hunting efficiency is highest. Through these combined strategies, the adults maximize the energetic return of chick provisioning.
Video of the Eurasian Scops Owl (courtesy of Péntek István)
Author: Shui-Ye You
Reference:
Torre I et al. (2026). Selective Predation and Chick Provisioning Rhythms in the European Scops Owl (Otus scops). Diversity.
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