Abundance and community structure of birds breeding in Kalahari woodland used as rangelandAcronym: MCNB-Kopij-2020
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.
The study was conducted in the Sachinga Livestock Development Centre of the Ministry of Agriculture of the Namibian Government. The centre is situated in NE Namibia, in the Zambezi region, about 40 km west of Katima Mulilo, between S17.39.40-S17.40.20 and E 24.23.55-E24.24.02. The Centre is a ranch of 3,243 ha. Most of the Sachinga LDC is covered by teak woodland, with smaller portion of Burkea-Kisat-False Mopane woodland and Omuramba grassland. The natural vegetation is well-preserved and represented by three classes of Kalahari woodland: 1) Colophospermum mopane , with two dominant associations: Nymphaea nouchali–Eragrostis rotifer which contains water species, and Combretum imberbe–Acacia nigrescens in association with sparse woodlands; 2) Baikiaea plurijuga woodland, comprising Guibourtia coleospherma–Burkea africana Association and Combretum collinum–Boscia albitrunca association; and 3) Baikiaea plurijuga – Terminalia sericea class with Pterocarpus angolensis–Diploryhnchus condylocarpon association, Dalbergia martinii–Berchemia discolor association, and Acacia fleckii–Baphia massaiensis association (Lushetile, 2009).
All birds showing breeding (e.g. transporting nesting material, constructing nests, feeding chicks etc.) or territorial (e.g. singing males) behaviour were recorded. Special attention was paid to simultaneously singing males, as they were important in determining the number of occupied territories. Special care was taken not to count the same birds twice, as this could overestimate the number of territories.
The number of breeding pairs was estimated for each section on each transect. The maximumnumber of breeding pairs at each survey and on each section was assumed as the real number of breeding pairs. The total number of breeding pairs of each species on a particular transect was calculated as the total of maximum numbers recorded on each section within the transect.
The following indices were used to characterise diversity, evenness and similarity between the communities:
1) Shannon’s diversity index: H’ = -∑ pi ln pi
where: pi is the proportion of breeding pairs belonging to the ith species
2) Simpson’s diversity index: D = ((∑n(n-1))/N(N-1)
where: n – total number of breeding pairs belonging to a given species, N – total number of breeding pairs of all species
3) Pielou’s evenness index: J’ = (-∑ pi ln pi)/ln S
where pi is the proportion of breeding pairs belonging to the ith species; S – total number of species. J’ varies between 0 and 1. The lower the variation between species in a community, the higher the J’.
4) Community dominance index: DI = (n1 + n2)/N
where n1, n2 – number of pairs of the two most abundant species, N – total number of pairs of all species.
5) Sörensen’s Coefficient: I = 2C/A+B
where A – the number of bird species in one plot, B – the number of bird species in another plot, C – the number of bird species common to both plots.
Systematics and nomenclature of bird species follow Hockey et al. (2005). Scientific names of bird species are listed in appendix 1.
Type of content
Includes: point occurrence data.
Kopij, G., 2020. Abundance and community structure of birds breeding in Kalahari woodland used as rangeland. Museu de Ciències Naturals de Barcelona. Dataset/Occurrence:
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