Diversidade e composição de aves no distrito de Nacala-à-Velha: um teste à teoria do stress ambiental

Abstract

The composition of biodiversity and the variability of species in a given location depend on the vegetation structure and the activities carried out by man. Human occupation and its activities create barriers to the mobility of wild species and lead to stochastic processes. Species richness is compromised, specialist species and trophic guilds reduce in number. This work aimed to test the theory of Environmental Stress in bird species as a response to human influence in the district of Nacala-à-velha, Nampula Province. Birds were sampled using the fixed point method, which consists of standing at a point and taking an inventory of all the species seen and heard. The species sampled were identified and grouped into trophic groups. Human influence was studied by digitising the houses in the study area using Google Earth. A 500m2 grid was built to delimit and georeference the study area.The land use and cover map was drawn up using ArcGis software in the ArcMap package, where it was possible to identify the existing habitats in the study area. The habitats sampled were ordered according to the degree of disturbance. Bird diversity was determined using the Shannon-Winner index, bird richness through the total number of species found and composition through the guilds in each habitat. Species diversity was compared between the habitats in a paired manner using the ANOVA-one way test, at a significance level of 5 per cent. A total of 56 bird species were recorded, distributed among 27 families and 11 orders. Of the species recorded, 45% are insectivorous, 17% are omnivorous and granivorous at the same time, 11% are frugivorous, 6% are piscivorous and 4% are nectarivorous. The first three guilds were the most representative in all habitats. The order with the highest number of species was the Passeriliform and the order with the lowest number of species was the Colliform. The Shannon-Wiener specific diversity index (H') showed significant differences between the habitats sampled (ANOVA, F= 1.7475; gl= 56; p=0.0018). The highest diversity index was observed in Open Forest 3 with 4.74 and the lowest index was observed in Open Forest and Marshes with 0.72. The results obtained in this study show that environmental stress influences the diversity and composition of birds, in such a way that the number of bird species reduces as the stress becomes more pronounced(TRADUÇAO NOSSA)