Seasonal variation in waterbird assemblage in the Mahango Game Reserve, north-eastern Namibia

Grzegorz Kopij,Mark Paxton

doi:10.4314/wsa.v45i2.13

Grzegorz Kopij, Mark Paxton

Open Access

https://doi.org/10.4314/wsa.v45i2.13

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Abstract

There are few African studies on seasonal changes in the waterbird assemblages in river ecosystems. Tropical freshwater ecosystems are regarded as more stable habitats over the year than terrestrial ones. The same could be expected in regard to the bird fauna associated with such ecosystems. In order to test if waterbird asembalges followed the stable ecosystem paradigm a study was undertaken in the Okavango River, in the Mahango Game Reserve, north-eastern Namibia. Counts of all waterbirds were conducted in wet and dry seasons during 2001–2006. In total, 88 waterbird species were recorded. In wet seasons the number was slightly lower (N = 75) than in dry seasons (N = 78) (chi-square test: χ2 = 0.06; p > 0.05). The total number of individuals of all resident species recorded in wet seasons was unexpectedly much lower in wet (N = 9 979) than in dry seasons (N = 15 501) (chi-square test: χ2 = 1 196; p < 0.01). In wet seasons, Collared Pratincole, Blacksmith Lapwing, African Openbill Stork and African Darter dominated (58.8%), while in the dry season: White-faced Duck, Spur-winged Goose, African Skimmer, African Reed Cormorant, African Darter and Squacco Heron contributed 60.8% to the overall abundance. Diversity indices were similar in both seasons.

Highlights

In comparison with terrestrial habitats, tropical freshwater ecosystems are regarded as more stable over the year, as one of the most important ecological factors, water, is not a limiting factor in this case
The same could be expected in regard to the bird fauna associated with such ecosystems, but waterbirds are known to be seasonally highly mobile under such conditions (Cumming et al, 2012)
86 waterbird species were recorded in the Okavango River in Mahango Game Reserve from 2001–2006 (Table 1A, Appendix)

Summary

Introduction

In comparison with terrestrial habitats, tropical freshwater ecosystems are regarded as more stable over the year, as one of the most important ecological factors, water, is not a limiting factor in this case. Kelejta-Summers et al (2001) studied year-to-year and seasonal changes in waterbird communities at the Cape Flats Sewage Treatment Works in Strandfontein near Cape Town. Swanepoel et al (2009) studied year-to-year changes in waterbirds in an impoundment, the Theewaterskloof Dam in the Western Cape, South Africa. Mundava et al (2013) investigated year-to-year and seasonal changes in the composition and abundance of waterbirds in two artificial lakes (Chivero and Manyame) near Harare, Zimbabwe. Cumming et al (2013) studied seasonal changes in waterbirds in a natural lake and wetlands at Barberspan, South Africa. All of these standing and mostly artificial freshwater ecosystems constitute, quite different ecological settings in comparision with a large perennial river

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