THE BIRDS OF SIKKIM: AN ANALYSIS OF ELEVATIONAL DISTRIBUTION, ENDEMISM AND THREATS

ABSTRACT 2 ikkim, a small state (geographical area 7096 km ) located in the northeast part of India, is a paradise for ornithologists. Many explorers and scientists including famous ornithologist Salim Ali visited Sikkim for study S purpose. Most of the publications are based on taxonomy and systematics except a few recent ecological studies. We generated a database of birds of Sikkim based on literature and field studies during 2003-2006 with special reference to elevational distribution, endemism and threat. The state was divided into six zones based on vegetation types and altitudes. Generated database of birds of Sikkim shows a total of 574 species belonging to 253 genera and 55 families under 16 avian orders. Along the elevation gradient, species richness followed unimodal pattern with maximum species at mid-elevation zone. The number of habitat specialist (species occurring in single elevation zone) are more in the lowest and highest zones. A high turnover of species was observed along the elevation gradient with a few species showing wider distribution range. Ten eastern Himalayan endemic species are reported to occur in Sikkim. Of the total species, 17 are threatened (1 Endangered, 3 Critically Endangered and 13 Vulnerable) and 10 near threatened bird species. It is suggested that further study on birds of Sikkim should focus on ecology and habitat requirements of individual species especially of rare, threatened and endemics

Do sub-groups of butterflies display different elevational distribution patterns in the Eastern Himalaya, India?

Understanding the pattern of biodiversity along environmental gradients helps in identifying diversity hotspot areas that can be prioritized for conservation. While the elevational distribution of several taxa has been studied, responses of the sub-groups within a taxon to elevation and its associated factors are not properly understood. Here we study species richness and butterfly density along an elevation gradient in Sikkim, Eastern Himalaya, India and explore the underlying causes of the patterns. We sampled butterflies using a fixed-width point count method in 16 elevational bands (150–200 m intervals), between a range of 300 and 3300 m a.s.l. We categorized butterflies into various sub-groups based on family, range size, biogeographic affinity, and host-plant specialization. We recorded 3603 individuals and 253 species of butterflies after the completion of 1860 point counts. Overall, species richness in the majority of the sub-groups (except for Riodinidae and Palearctic species) declines with elevation, as does the density of almost all the sub-groups. From a selection of environmental factors, annual actual evapotranspiration has the strongest effect on the species richness pattern of butterflies as well as on the density of the overall butterfly community, especially the Lycaenidae family. The richness and density of butterfly groups display varied responses to the richness and density of trees and shrubs. The conducive climatic conditions and diverse habitats in the lower valleys of the Eastern Himalaya support a high diversity of butterflies (with majority of small range species) and thus warrants conservation attention.publishedVersio

Elevational Gradients in Bird Diversity in the Eastern Himalaya: An Evaluation of Distribution Patterns and Their Underlying Mechanisms

BACKGROUND: Understanding diversity patterns and the mechanisms underlying those patterns along elevational gradients is critically important for conservation efforts in montane ecosystems, especially those that are biodiversity hotspots. Despite recent advances, consensus on the underlying causes, or even the relative influence of a suite of factors on elevational diversity patterns has remained elusive. METHODS AND PRINCIPAL FINDINGS: We examined patterns of species richness, density and range size distribution of birds, and the suite of biotic and abiotic factors (primary productivity, habitat variables, climatic factors and geometric constraints) that governs diversity along a 4500-m elevational gradient in the Eastern Himalayan region, a biodiversity hotspot within the world's tallest mountains. We used point count methods for sampling birds and quadrats for estimating vegetation at 22 sites along the elevational gradient. We found that species richness increased to approximately 2000 m, then declined. We found no evidence that geometric constraints influenced this pattern, whereas actual evapotranspiration (a surrogate for primary productivity) and various habitat variables (plant species richness, shrub density and basal area of trees) accounted for most of the variation in bird species richness. We also observed that ranges of most bird species were narrow along the elevation gradient. We find little evidence to support Rapoport's rule for the birds of Sikkim region of the Himalaya. CONCLUSIONS AND SIGNIFICANCE: This study in the Eastern Himalaya indicates that species richness of birds is highest at intermediate elevations along one of the most extensive elevational gradients ever examined. Additionally, primary productivity and factors associated with habitat accounted for most of the variation in avian species richness. The diversity peak at intermediate elevations and the narrow elevational ranges of most species suggest important conservation implications: not only should mid-elevation areas be conserved, but the entire gradient requires equal conservation attention

Indigenous knowledge of Lepcha community for monitoring and conservation of birds

65-69The non-professional volunteers are commonly used in biodiversity assessment due to lack of experts. The bird identification skills of indigenous Lepcha community have been recognized and the accuracy of data generated by them has been assesed. Bird sampling was done using point count method along the transects in three locations in Dzongu, North Sikkim. Two observers, a trained ‘researcher’ and a local Lepcha folk referred as citizen scientist independently sampled birds (species by former and varieties by the latter). The mean number of species and varieties per point was not significantly different from each other. Gross accuracy of data collected by citizen scientist was high. These results showed that indigenous taxonomic knowledge of Lepcha community can be applied for biodiversity assessment programme provided the individual biasness of lumping and splitting is taken care

Do sub-groups of butterflies display different elevational distribution patterns in the Eastern Himalaya, India?

Understanding the pattern of biodiversity along environmental gradients helps in identifying diversity hotspot areas that can be prioritized for conservation. While the elevational distribution of several taxa has been studied, responses of the sub-groups within a taxon to elevation and its associated factors are not properly understood. Here we study species richness and butterfly density along an elevation gradient in Sikkim, Eastern Himalaya, India and explore the underlying causes of the patterns. We sampled butterflies using a fixed-width point count method in 16 elevational bands (150–200 m intervals), between a range of 300 and 3300 m a.s.l. We categorized butterflies into various sub-groups based on family, range size, biogeographic affinity, and host-plant specialization. We recorded 3603 individuals and 253 species of butterflies after the completion of 1860 point counts. Overall, species richness in the majority of the sub-groups (except for Riodinidae and Palearctic species) declines with elevation, as does the density of almost all the sub-groups. From a selection of environmental factors, annual actual evapotranspiration has the strongest effect on the species richness pattern of butterflies as well as on the density of the overall butterfly community, especially the Lycaenidae family. The richness and density of butterfly groups display varied responses to the richness and density of trees and shrubs. The conducive climatic conditions and diverse habitats in the lower valleys of the Eastern Himalaya support a high diversity of butterflies (with majority of small range species) and thus warrants conservation attention

Do sub-groups of butterflies display different elevational distribution patterns in the Eastern Himalaya, India?

Understanding the pattern of biodiversity along environmental gradients helps in identifying diversity hotspot areas that can be prioritized for conservation. While the elevational distribution of several taxa has been studied, responses of the sub-groups within a taxon to elevation and its associated factors are not properly understood. Here we study species richness and butterfly density along an elevation gradient in Sikkim, Eastern Himalaya, India and explore the underlying causes of the patterns. We sampled butterflies using a fixed-width point count method in 16 elevational bands (150–200 m intervals), between a range of 300 and 3300 m a.s.l. We categorized butterflies into various sub-groups based on family, range size, biogeographic affinity, and host-plant specialization. We recorded 3603 individuals and 253 species of butterflies after the completion of 1860 point counts. Overall, species richness in the majority of the sub-groups (except for Riodinidae and Palearctic species) declines with elevation, as does the density of almost all the sub-groups. From a selection of environmental factors, annual actual evapotranspiration has the strongest effect on the species richness pattern of butterflies as well as on the density of the overall butterfly community, especially the Lycaenidae family. The richness and density of butterfly groups display varied responses to the richness and density of trees and shrubs. The conducive climatic conditions and diverse habitats in the lower valleys of the Eastern Himalaya support a high diversity of butterflies (with majority of small range species) and thus warrants conservation attention

Ecological niche modelling of two water-dependant birds informs the conservation needs of riverine ecosystems outside protected area network in the Eastern Himalaya, India.

Common species often play vital roles in ecosystem functions and processes. Globally, conservation strategies are mostly focused on threatened species and rarely explored the potential of using common species as indicators of critical ecosystems. The Himalayan mountains have unique riverine ecosystems harbouring high diversity of specialist river birds. Ecological niche modelling provides effective tools to predict suitable habitats of a species and identify habitats for conservation. We used two common water-dependent bird species, Blue Whistling Thrush and White-capped Water Redstart as indicators of riverine ecosystems within the Sikkim Himalayan region and predicted their suitable habitats using an ensemble modelling approach. We selected six predictor variables for the final model including three bioclimatic and three topographic variables. For both species, bioclimatic variables such as mean annual temperature and precipitation were the most important factors compared to topographic variables. At least 70 percent of the most suitable habitats are distributed below 2000 m elevation alongside major drainages. Also, most of their potential habitats are distributed outside the protected area networks in the region. This habitat suitability pattern may be applied to other sympatric species in the region. Since major water bodies in Sikkim are largely affected by developmental activities and climate change, these riverine birds might face threats of losing suitable habitats. We recommend a dynamic approach to evaluate the habitat quality of riverine birds, especially outside protected area networks in the region to plan conservation strategies. This approach will ensure habitat conservation of many water-dependent birds and other taxa associated with the riverine ecosystems of the Eastern Himalaya