Raman, T.R. ShankarJohnsingh, A.J.T.2025-01-131995http://192.168.202.180:4000/handle/123456789/60The 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.enBirdsCommunity structureSpecies diversityDampa tiger ReserveMizoramShifting cultivationJhum cultivationThesis