Abundance and community structure of birds breeding in Kalahari woodland used as rangeland

G Kopij

doi:10.32800/amz.2020.18.0101

Abstract

The line transect method was applied to assess the linear index of abundance and community structure of birds breeding in an area of Kalahari woodland used as range land for cattle. Four transects were designed along roads traversing the ranch. Each transect was 2.5 km long and was surveyed three times in 2014 and 2015. A total of 47 bird species were recorded but only 25-31 species were recorded on any particular transect. In the neighbouring pristine Kalahari woodland, the number of bird species on a12 km long transect was much higher (n = 88), and ranged in some sections (each 1.2 km in length) from 35 to 53. On any particular section, the number of dominant species ranged from 5 to 7, and their cumulative dominance on each section was similar, ranging from 53-56 %, while the community dominance index ranged from 0.23 to 0.35. The most numerous species were the Cape turtle dove and emerald-spotted wood dove, which were dominant on all sections. Together they comprised 28 % of all breeding birds. The avian community in the Kalahari woodland in Sachinga LDC did not differ from the neighbouring pristine woodland either in terms of species diversity or evenness. However, it differed significantly in terms of species richness, the proportion of main ecological guilds, and linear index of abundance of particular species. These differences could be mainly due to the structure of woody vegetation, which is much thicker in Sachinga than in the pristine woodland not used as pasture for cattle. The thickening of this vegetation on the ranch could have been caused by heavy grazing pressure by the cattle. Data published through GBIF (Doi: https://doi.org/10.15470/rova7r)

Highlights

In all parts of Africa, the expansion and intensity of agriculture pose a major threat to biodiversity through the conversion of natural habitats to agrocenosis, fragmentation and degradation
In some places, where selected biota were carefully surveyed in agrocenosis, it has been shown that they may well preserve certain communities, for example birds (Kopij, 1998, 2006, 2013, 2015, 2018; Ratclife and Crowe, 2001; Bolwig et al, 2006; Humle, 2007; Mulwa et al, 2012; Nadng’ang’a et al, 2013)
500 bird species have been recorded in this biome (Kopij, 2016, 2017)

Summary

Introduction

In all parts of Africa, the expansion and intensity of agriculture pose a major threat to biodiversity through the conversion of natural habitats to agrocenosis, fragmentation and degradation. In some places, where selected biota were carefully surveyed in agrocenosis, it has been shown that they may well preserve certain communities, for example birds (Kopij, 1998, 2006, 2013, 2015, 2018; Ratclife and Crowe, 2001; Bolwig et al, 2006; Humle, 2007; Mulwa et al, 2012; Nadng’ang’a et al, 2013) This is especially evident when traditional agriculture is established within woodlands and wet savannas. One of the largest broadleaved savanna type forests in Namibia is the Kalahari woodland It occupies about 600,000 km in Kavango West, Kavango East, Zambezi, and eastern parts of Ohangwena and Oshikoto regions (Mendelsohn et al, 2009). 500 bird species have been recorded in this biome (Kopij, 2016, 2017)

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