Habitat determinants of species occupancy and niche partitioning among sympatric owlets: the paradoxical role of agricultural lands for the endangered Forest Owlet, Athene blewitti

Abstract

Species with highly restricted distributions are intriguing especially when they co-occur with similar and related species that are more widely distributed. They are also of conservation concern because of their restricted distributions and low population size. The Forest Owlet (Athene blewitti) is an endangered species endemic to the central Indian landscape that occurs in apparently unconnected pockets. Two other species of owlets, with wide distributions in India, Jungle Owlet (Glaucidium radiatum) and Spotted Owlet (Athene brama) co-occur with Forest Owlet. Understanding how species use the habitat matrix is central to prioritizing conservation action. We studied the three species across an extensive part of the predicted range of Forest Owlets through 350 surveys.Our results indicate that Jungle Owlet occupancy (ψ = 0.5896, SE = 0.08) was highest, followed by Forest Owlet (ψ = 0.2517, SE = 0.10), and Spotted Owlet (ψ = 0.1781, SE = 0.07). The Forest Owlet showed a preference for stands of forests with large trees but not necessarily with closed canopies, as well as open habitats (agricultural land cover). The Spotted Owlet showed a preference for agricultural land cover with lower litter and bare ground cover. In contrast, the Jungle Owlet showed a preference for dense forest and canopy cover. The preference for agricultural cover by the Forest Owlet provides important insights into our understanding of the ecology of this owlet. Most significantly, it brings up several conservation challenges for managing this endangered species across a human-use landscape.RESUMEN. Las especies con una distribución altamente restringida son intrigantes especialmente cuando co-occurren con especies cercanamente emparentadas y similares que están más ampliamente distribuidas. Estas especies son también de interés para la conservación por su distribución restringida y bajo tamaño poblacional. Athene blewitti es una especie amenazada y endémica al paisaje del centro de India donde se encuentra en bolsillos de hábitat aparentemente desconectados. Otras dos especies de búhos, con una amplia distribución en India, Glaucidium radiatum y Athene brama co-occurren con Athene blewitti. Comprender como la especie utiliza la matriz del hábitat es central para priorizar acciones de conservación. Estudiamos las tres especies a lo largo de una porción extensiva del rango predicho de Athene blewitti usando 350 muestreos. Nuestros resultados indican que la ocupación de Glaucidium radiatum (ψ = 0.5896, SE = 0.08) fue la más alta, seguida por Athene blewitti (ψ = 0.2517, SE = 0.10) y Athene brama (ψ = 0.1781, SE = 0.07). Athene blewitti mostro una preferencia por fragmentos de bosque con árboles grandes, pero no necesariamente con dosel cerrado, así como hábitats abiertos (cobertura de agricultura). En contraste, Athene brama mostró una preferencia por bosque denso y con alta cobertura de dosel. La preferencia por coberturas de agricultura por parte de Athene blewitti provee información importante para nuestro entendimiento de la ecología de e...

Playback-aided surveys and acoustic monitoring in the detection of the Endangered Forest OwletAthene blewitti

“…We collated three past datasets across which we based our resurveys. The earliest dataset was from 1988-1991(Worah 1991, denoted hereafter as Worah 1990 by the year of the survey; and a decade later, in 2000 (Trivedi 2006), hereafter Trivedi 2000; and the latest, almost two decades later in 2018-2019 by (Khan et al 2023) -hereafter Khan 2019. All study years are denoted by the year of surveys and not by the year of publication.…”

“…We find that even with playback, there is variation in the detection of this rare species. Khan et al (2023) note that the detection probability of the species is ~70% in Dang with multiple temporal replicates. Of the 18 grids where they detected Forest Owlet in Dang, 13 (72%) grids had positive detections in all four of their survey replicates.…”

“…The first information on the Forest Owlet vocalizations and behaviour was provided by (Rasmussen and Ishtiaq 1999), and only more recent surveys (Ishtiaq and Rahmani 2004;Mehta et al 2008;Khan et al 2023), were able to use this method. We note that most numbers of reports of the Forest Owlet have increased since the publication of its vocalizations.…”

“…The location records of this species have increased since the recordings of its vocalisations have become more accessible. Today, playback of its calls is used in various detection-based studies (Mehta et al 2008(Mehta et al , 2017Khan et al 2023) One of the areas where the Forest Owlet is being increasingly recorded is the Dang area in Gujarat, at the northern edge of the Western Ghats. The first records of Forest Owlet from Dang were in 2014 (Patel et al 2015), and since then, they have been increasingly recorded from this region.…”

“…Although it may not be possible to answer this question comprehensively, we repurposed two previous datasets of surveys from 1990 (Worah 1991), 2000(Trivedi 2006, and a recent occupancy survey in 2019 (Khan et al 2023) and re-surveyed these locations with traditional and acoustic-aided methods. We also examined differences in climate in the time intervening the surveys.…”