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Owls hunt for their prey, seize them and carry off. They are nocturnal with terrific binocular vision, hook-tipped beaks and sharp curved claws perfect for lifting prey from the ground. But what do owls specifically hunt for and how do researchers go about studying owl diet? Do they sit and observe the owls for days on end? Well, that is practically impossible! What is it then that the researchers look for?
An Indian Eagle Owl at its roosting site in Tamil Nadu. Video by T. Siva
Owls’ diet is studied through analysis of their regurgitated ‘pellets’. Once owls hunt, they swallow their prey whole or tear it into pieces before consuming it. The parts such as bone, teeth, fur and invertebrate exoskeleton cannot be digested by the owls. Instead, these undigested remains are turned into a ball called a pellet. These pellets are later vomited out through the mouth/ beak. It is these pellets which the researchers bring back to the lab and carefully clean and dissect, to understand the diet of the owls!
Owl pellets with undigested bones and fur. Photos by T. Siva
Such a study on the diet of the majestic Indian Eagle Owl (Bubo bengalensis) was conducted in Musiri Taluk of Tiruchirappalli District, Tamil Nadu from April to September 2017 by researchers T. Siva, P. Neelanarayanan and V. V. Rao of Nehru Memorial College, Tamil Nadu and PJTS Agricultural University, Telangana. The Indian Eagle-owl is found only in the Indian subcontinent and inhabits rocky hillocks, earth cuttings and bushes. Once the sun sets, these owls hunt for their food in agricultural crop fields, water bodies and hills. Pellets of Indian Eagle Owl were found often under their roosting/ nesting sites in the hillocks. Researchers collected and analysed a whopping 1082 regurgitated pellets from 3 roosting sites in Tamil Nadu.
The different sizes of pellets of the Indian Eagle Owl found at the study site in Musiri Taluk of Tiruchirappalli District, Tamil Nadu. Photo by T. Siva
Undigested exoskeleton of insects, chelicerae of scorpions and bones of rodents and birds found in the pellets. Photos by T.Siva
The pellet analysis revealed that almost 65% of the diet of the owls consists of rodents like the Lesser bandicoot rat, Greater bandicoot rat, Indian palm squirrel, Soft-furred rat, Little Indian field mouse, Black rat, Asian house shrew and the Indian gerbil. The remaining 34% includes amphibians, reptiles, insects like the rhinoceros beetle, arachnids like spiders and scorpions were also found in the owl pellets! Interestingly, pellets determine that even birds and bats can form a small part of the Indian Eagle-owl diet. Careful analysis revealed that the majority of pellets consisted of more than one prey item suggesting that owls hunt more than one prey every day.
Owls mainly feast on rodents. Insects and arachnids were also a small part of the diet of Indian Eagle owls!
Studies on animal diet help understand the ecosystem it inhabits and it’s functioning. Information on prey-predator relationships allows for proper management of the area and gives an overview of the role the different species play in its ecosystem. It is obvious from the results of the present investigation that these owls hunt both commensal and field rodents and insects, which are major pests in agricultural crop fields! The study highlights the importance of Indian Eagle Owls, which render a silent service to the farmers in the agro-ecosystems. Such a study emphasizes the importance of owls in an ecosystem and helps understand and strengthen our pledge to protect them in their natural environment.
Typical roosting habitat of the Indian Eagle Owl, around agricultural fields. Photo by: T. Siva
Source: Siva, T., P. Neelanarayanan & V. V. Rao (2019). Food composition of Indian Eagle Owl Bubo Bengalensis Franklin (Aves: Strigiformes: Strigidae) from Tiruchirappalli District, Tamil Nadu, India. Journal of Threatened Taxa 11(5): 13545–13551.
Article contributed by Pratiksha Sail, edited by Nikita Gupta and Devica Ranade