Diet preference of common mynas (Sturnus tristis) in urban areas of Pietermaritzburg and Durban, KwaZulu-Natal.
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Date
2017
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Abstract
Urbanization is one of the anthropogenic land use changes with a negative impact on biodiversity generally. However, some species are persisting well in urban areas and are termed urban exploiters. One of these species is the common myna (Sturnus tristis). It is also considered amongst the 100 worst alien invasive birds globally. As relatively little is known about the factors that affect common mynas invasive ability and urban persistence, aspects of their diet were investigated. Consequently, the main aims of this project were to investigate the macronutrient preference, sugar type and concentration preference, and assimilation efficiency of captive common mynas in the laboratory from July 2016 to March 2017. In addition, patterns of occurrence of common mynas in urban areas of Pietermaritzburg and Durban, KwaZulu-Natal, South Africa, and the influence of supplementary feeding and anthropogenic foods on their diet were investigated using questionnaires.
Common mynas (n = 10) macronutrient preference was investigated in the laboratory where they were offered pairwise choices of three different diets (high in lipids diet, high in soluble carbohydrates (including sucrose) diet, and high in protein diet). Common mynas significantly preferred the high in lipids diet compared with either the high in protein diet or the high in carbohydrate diets. Common mynas (n = 7) were offered pairwise choices of three nectars (glucose, fructose and sucrose) to investigate their sugar type and concentration preference. Birds showed a significant preference for diluted glucose when given a choice of nectars. The sugar content of their excreta showed that they were unable to digest and absorb sucrose in nectar.
Responses from the questionnaires showed that common mynas were found in the two study cities and were abundant year around. Results also showed that they were feeding mostly on anthropogenic foods compared with natural foods. Anthropogenic supplementary feeding has likely influenced the occurrence of common mynas because they follow food resources (human food waste) in urban areas and therefore successfully persist through lean periods. Further research is needed to help understand the ecology and behaviour of common mynas in order to get insights on how to monitor and control them in urban areas, in particular in South Africa where their range is expanding. Common mynas behaviour is currently poorly documented in South Africa. Since these are alien invasive birds with negative impacts in other countries, more research, especially on their behaviour, is required to prevent their negative impacts occurring in South Africa.
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Master of Science in Biological Science. University of KwaZulu-Natal. Durban, 2017.