M Sc Dissertation(WII)

Now showing 1 - 3 of 3

Avian Communities in the Riparian Areas of Bori Wildlife Sanctuary, India
(Wildlife Institute of India, Dehradun, 1993) Pai, Ashwini; Johnsingh, A.J.T.
Riparian areas are important as special habitats and corridors for wildlife. However, in India, riparian areas have not been studied to any detail. Also, not much is known about the avifauna of riparian habitats. The vegetation near a riparian area tends to be dense and hence distinct owing to constant availability of water. Riparian areas come under heavy use, both by livestock as well as wild animals because of the presence of water and forage. The avifauna of riparian areas is rich due to its floral complexity and structure and resources like fish and insects. This study quantified bird species diversity, avian guilds and avian community structure found in four riparian areas ( a flood plain, a riparian scrub, a disturbed nulla and an undisturbed nulla) of Bori sanctuary in Central India. The riparian areas were compared with the adjoining deciduous forest for avifaunal differences. Vegetation was studies along the riparian areas and the deciduous forests, using circular plots. Tree and shrub densities, vertical stratification of foliage and species richness were quantified. Line transects were used to estimate bird ,species richness and abundance. Bird species richness was correlated to negative variables for the two seasons. In summer the BSR was highly correlated with CC and in winters with CC. Stepwise multiple regression was used to create a habitat model for BSR in summer and in winter. Community patterns show seasonal change and also respond to structural changes of habitat.
Shifting Cultivation and Conservation of Tropical Forest Bird Communities in Mizoram, North-East India
(Wildlife Institute of India, Dehradun, 1995) Raman, T.R. Shankar; Johnsingh, A.J.T.
The impact of the traditional practice of shifting cultivation or jhum on evergreen and semievergreen forest bird communities was studied in Dampa Tiger Reserve in western Mizoram, north-east India. Bird community changes through vegetation succession was studied by comparing sites that were jhum 1,5, 10,25, and 100 years ago with primary forest that has never been cleared. Systematic line transect sampling showed that bird species richness, abundance, and diversity, increased from very low levels in the I-year old fallow to maximum levels in undisturbed and 100-year old forest, with intermediate values in the 5-25 year fallows (bamboo forests). The trend of increase was not linear but hyperbolic, with a rapid increase up to 25 years approaching an asymptote at 100 years . Similarity in bird community composition between two sites was inversely related to the difference in the logarithm of their ages. Trends in bird communities were closely related to changes during vegetation succession. Vegetation variables measured were summarised by Principal Components Analysis, which yielded two components (PCI and PC2), accounting for 91.9% percent of the variance in the data-set. PCI was correlated positively with tree density, woody plant species richness, vertical stratification, depth of leaf litter, and canopy cover, and negatively with horizontal heterogeneity in the vegetation. PC 1 thus represents the changes occurring during woody plant succession. PC2 was correlated strongly with bamboo density, which shows an increase from 1 to at least 25 years after jhuming and declines in mature forest, and this axis was taken to represent bamboo succession . Bird species richness and abundance were positively correlated with PCI (woody plant succession). When the effects of PC I were removed by partial correlation, both variables were negatively correlated with PC2. The number of species in guilds such as frugivores, nectarivore insectivores, bark-feeder, canopy insectivores were positively related to PC 1. Only the bamboo-substrate feeding guild was related to PC2. These results suggest that bird community structure is largely determined by ,woody plant succession. Mature forests were found to be the main habitat for forest specialists, rare birds, and altitudinal migrants. Thirteen specialised open-country birds and two species of latitudinal migrants occurred mainly in jhumed areas. These were generally common and widespread species that will likely persist in highly disturbed areas. In terms of conservation of the forest birds of the region, mature forests are most important. The major implication of the study relates to the observed hyperbolic changes in bird species richness, and vegetation variables such as woody plant species richness. This suggests species loss in jhumed areas will be a logarithmic and not linear function of the age, i.e. a decline in jhum cycle from 100 to 50 years Ca 2-fold difference) will have less impact than a decline from 25 to 5 years Ca 5-fold difference). This implies that under the 5-10 year jhum cycles that are prevalent in most parts of north-east India today, there will be substantial losses in bird species richness. This effect may be accentuated if primary forests are not part of the jhum habitat matrix.
A Study of Heterospecific Flocking and Nonbreeding Bird Community Structure of Rajaji National Park
(Wildlife Institute of India, Dehradun, 1991) Rai, Nitin D.; Johnsingh, A.J.T.
Many workers have found a direct relationship between bird community structure and vegetation structure. To investigate this and describe the heterospecific flocking behaviour of nonbreeding birds I sampled five habitat types in the Dholkhand range of Rajaji National Park, U.P., India. Inter-habitat differences in flocking and bird community structure were considered. I used the line transect technique to sample bird communities. Mixed species flocks were observed to investigate why birds flock. The guild structure based on diet and foraging strategy showed a marked difference between habitats. Species richness was estimated using rarefaction analysis, a procedure that standardizes the unequal area of the different sites. I used a correlational approach to answer the question – what determines bird species richness ? Foliage height diversity, canopy cover, canopy height, canopy height difference, tree density, tree species numbers and cross sectional area, were used as the vegetation variables. Results indicate that none of the variables have strong predictive value though tree species number which is the only floristic measure of the habitats has a consistent influence independent of sample size. The guild structures suggest that the bird communities vary with floristic aspects, of the habitats. To test my hypothesis that flocking is a response to food availability I related bird densities, which is an indicator of food availability, to flocking tendencies and found a inverse relationship. I also found behavioural evidence to suggest that flocking is also an anti-predatory strategy.

M Sc Dissertation(WII)

Browse

Filters

Settings

Sort By

Results per page

Search Results