Effect of rainfall on the structure and population densities of birds breeding in a suburb of Windhoek, Namibia

A bird community was quantified in the suburb of Olympia (200 ha) in the city of Windhoek, Namibia. Two years (2014 and 2020) were selected to examine the impact of rainfall and sub- urb development on species diversity and population densities of the selected bird species in this community. The total amount of rainfall in Windhoek in 2014 was much higher than in 2020 (475 mm and 275 mm, respectively). In total, 36 breeding bird species were recorded in the study area in 2014 and 2020: 27 spe- cies in 2014 and 31 species in 2020. The number of species com- mon in 2014 and 2020 was 17. The Sörensen’s Similarity Index was therefore rather low (0.59). In overall, population density of 25 selected bird species was much higher in 2020 than in 2014. Population densities of the Laughing Dove, the Southern Masked Weaver, and Chestnut-vented Warbler in 2014 and 2020 were statistically different, whereas population densities of the Red- headed Finch were similar in both years compared. The breeding bird community in Olympia suburb does not ap- pear to be stable over years, both in regard to species composition and population densities of particular species. This instability may be linked to constant property development of this suburb and around it. Olympia suburb borders on the periphery of the city, which is a savanna slowly transformed into another suburb. Un- der drought conditions, some species from these surroundings may be attracted to the suburbs by water and food. Hence, con- trary to expectation, densities of some species in the suburbs in the year with low rainfall are higher.