The flight of the hornbill: drift and diffusion in arboreal avian movement

Capturing movement of animals in mathematical models has long been a keenly pursued direction of research1 . Any good model of animal movement is built upon information about the animal’s environment and the available resources including whether prey is in abundance or scarce, densely distributed or sparse2 . Such an approach could enable the identification of certain quantities or measures from the model that are species-specific characteristics. We propose here a mechanistic model to describe the movement of two species of Asian hornbills in a resource-abundant heterogenous landscape which includes degraded forests and human settlements. Hornbill telemetry data was used to this end. The birds show a bias both towards features of attraction such as nesting and roosting sites as well as possible bias away from points of repulsion such as human presence. These biases are accounted for with suitable potentials. The spatial patterns of movement are analyzed using the Fokker–Planck equation, which helps explain the variation in movement of different individuals. Search times to target locations were calculated using first passage time equations dual to the Fokker–Planck equations. We also find that the diffusion coefficients are larger for breeding birds than for non-breeding ones—a manifestation of repeated switching of directions to move back to the nest from foraging sites. The degree of directedness towards nests and roosts is captured by the drift coefficients. Non-breeding hornbills show similar values of the ratio of the two coefficients irrespective of the fact that their movement data is available from different seasons. Therefore, the ratio of drift to diffusion coefficients is indicative of an individual’s breeding status, as seen from available data. It could possibly also characterize different species. For all individuals, first passage times increase with proximity to human settlements, in agreement with the premise that anthropogenic activities close to nesting/roosting sites are not desirable

Impact of Dams on Riparian Frog Communities in the Southern Western Ghats, India

The Western Ghats is a global biodiversity hotspot and home to diverse and unique assemblages of amphibians. Several rivers originate from these mountains and hydropower is being tapped from them. The impacts of hydrological regulation of riparian ecosystems to wildlife and its habitat are poorly documented, and in particular the fate of frog populations is unknown. We examined the effects of dams on riparian frog communities in the Thamirabarani catchment in southern Western Ghats. We used nocturnal visual encounter surveys constrained for time, to document the species richness of frogs below and above the dam, and also at control sites in the same catchment. While we did not find differences in species richness below and above the dams, the frog community composition was significantly altered as a likely consequence of altered flow regime. The frog species compositions in control sites were similar to above-dam sites. Below-dam sites had a distinctly different species composition. Select endemic frog species appeared to be adversely impacted due to the dams. Below-dam sites had a greater proportion of generalist and widely distributed species. Dams in the Western Ghats appeared to adversely impact population of endemic species, particularly those belonging to the genus Nyctibatrachus that shows specialization for intact streams

Naniwadekar_Datta_TCS_Hornbill_Data

Contains details (date, trail identity and length, time, hornbill species identity, perpendicular distance of the sighting, flock size of the bird) of all the hornbill sightings during distance sampling for hornbill density estimation in Namdapha Tiger Reserve. The details of the total number of replicate walks and effort across each trail can also be found here. The details regarding total sampling effort can be found here https://tropicalconservationscience.mongabay.com/content/v6/TCS-2013-Vol6(6)_734-748_Naniwadekar-and-Datta.pdf

Data from: Spatial and temporal variation in hornbill densities in Namdapha Tiger Reserve, Arunachal Pradesh, north-east India

Asian hornbill populations are declining across their ranges because of hunting and deforestation. Five of the 32 Asian hornbill species occur in north-east India. However, vital information on their abundance from the region remains scanty. Understanding spatiotemporal variation in densities provides crucial information for formulating effective conservation strategies based on species-specific abundance patterns and population trends. We examined spatiotemporal variation in densities of four hornbill species in the Namdapha Tiger Reserve, a site identified as an important site for hornbill conservation in Asia. We collected data through variable-width line transect sampling (effort=842.1 km) in the non-breeding season from 2009-12 to estimate hornbill densities. We had 458 detections of four hornbill species. We have estimated White-throated Brown Hornbill densities (7.9 birds/km2) for the first time throughout its entire range. The mean Rufous-necked Hornbill densities (6.9 birds/km2) were higher than those reported elsewhere. Great (3.9 birds/km2) and Wreathed Hornbill (16.1 birds/km2) densities were comparable with other sites. The peak densities of all hornbill species in November-December are among the highest reported from Asia. Wreathed Hornbill densities showed temporal variation peaking in November-December (68 birds/km2) and drastically declining by March-April (1.3 birds/km2), indicating seasonal altitudinal movement to low-elevation areas outside the reserve during the breeding season. Our results underscored the spatial variation in hornbill distribution, with low densities of Great and the White-throated Brown hornbills in higher elevations. Our study demonstrates the global importance of Namdapha for hornbills, given its large area and high densities of four hornbill species

Diet and foraging behaviour of Purple Cochoa Cochoa purpurea in Namdapha National Park, India

Volume: 30Start Page: 145End Page: 14

New Distribution Record for Calotes Nemoricola Jerdon, 1853 from the Kudremukh Hills, Karnataka, India

Volume: 105Start Page: 99End Page: 9

NEW DISTRIBUTION RECORD FOR HEMIDACTYLUS PRASHADI SMITH, 1935 (FAMILY: GEKKONIDAE) FROM THE KUDREMUKH FOREST COMPLEX, KARNATAKA, INDIA

Volume: 107Start Page: 253End Page: 25

Naniwadekar_Datta_TCS_Hornbill_Data

Contains details (date, trail identity and length, time, hornbill species identity, perpendicular distance of the sighting, flock size of the bird) of all the hornbill sightings during distance sampling for hornbill density estimation in Namdapha Tiger Reserve. The details of the total number of replicate walks and effort across each trail can also be found here. The details regarding total sampling effort can be found here https://tropicalconservationscience.mongabay.com/content/v6/TCS-2013-Vol6(6)_734-748_Naniwadekar-and-Datta.pdf

SMJ_Shukla_etal_data_description

Data description of the gut passage dat

SMJ_Shukla_etal_gpt_data

Gut passage time data for five tree species (Aglaia spectabilis, Beilschmiedia assamica, Polyalthia simiarum, Livistona jenkinsiana, and Syzygium cumini) of Oriental Pied Hornbill, Rufous-necked Hornbill and Wreathed Hornbil