Does Southern Spotted Owlet Athene brama brama (Temminck, 1821) Serve as a Biocontrol Agent of Agricultural Pests? A Case Study from Cauvery Deltaic Region of Southern India

Abstract

Owl species congregate at pest-infested areas, and their role in biological control of agricultural pests has become significant. India is endowed with 62 species of owls, of which the spotted owlet Athene brama is the commonest and a widely distributed species. The species is regarded as a biocontrol agent of agricultural pests in India. To determine whether the southern spotted owlet Athene brama brama is serving as a biocontrol agent of agricultural pests in the Cauvery deltaic region of Tamil Nadu, southern India, we assessed their roost site selection and diet composition during 2007–2008. Roost selection was studied based on roost site characteristics observed from 22 roost sites. The results showed that the spotted owlets roosted more frequently close to human habitation (mean distance 41 ± 12.8 m) than agricultural fields (218 ± 50.7 m). All the roost sites observed have used trees as substrate. Among the six tree species used as substrate, Albizia saman (rain tree) was the most commonly used roost tree species. Tree species with 20–30 m height and 1–3 m gbh were most frequently used for roosting, likely due to the presence of more number of branches and dense foliage than nearby non-roost trees. Availability of suitable locations with better protection from weather and concealment to avoid the disturbance from humans and other birds appeared to influence the selection of roost species and size class by the southern spotted owlet. Diet composition was assessed indirectly, analyzing 55 regurgitated pellets collected from 12 roost sites. Diet items identified based on the undigested food remains in the pellet revealed that insects constituted the bulk of the owls’ diet (57%) followed by mammals (rodents) (24.4%), reptiles (7.8%), and birds (7.3%). However, among the prey groups, the mammalian prey contains more flesh per unit of body mass than insect, which is digestible by owl; thus, it is argued that mammals in the form of digestible part could have contributed more to the diet of owlet than any other taxa. The higher consumption of rodents and insects, which are potential pests of the agriculture ecosystems, by spotted owlets indicates the importance of the species as a prospective biocontrol agent of insect and rodent pests of agriculture in the study area. Despite their higher dependence on agricultural pests as food resources, reason for roosting closer to the human habituation could be due to inadequate roosting sites (mature trees) in agricultural areas. Thus creating awareness among local communities about the role of spotted owlets and the importance of maintaining a few mature trees in agricultural areas, as roost sites for owlets, would not only improve their population and ensure long-term conservation but also help controlling the agricultural pests effectively, without the rampant use of pesticide, which causes detrimental effect to the environment and biodiversity including the human beings.