Alien and Invasive Birds on Smallholdings

Alien invasive species are animals and plants that have been introduced to a country in which they were not naturally found in the past, and which have the potential to grow their population and range in that country. They cause economic or environmental harm or adversely affect human health.
In particular, they impact adversely upon biodiversity, including decline or elimination of native species – through competition, predation, ortransmission of pathogens – and the disruption of local ecosystems and ecosystem functions.
Twenty three bird species have been listed as alien invasives in South Africa by the National Environmental Management: Biodiversity Act’s Alien and Invasive Species List (NEMBA). Of these, only five have well established, growing populations: the mallard duck (Anas platyrhynchos), feral pigeon (Columba livia), common myna (Acridotheres tristis), common starling (Stumus vulgaris) and house sparrow (Passer domesticus).
Most smallholders will have encountered common mynas on their plots and many of us resent their presence.
The common myna is native to southern and south-eastern Asia and was introduced to South Africa in about 1900. A few individuals introduced into Natal multiplied into millions, and are now found over a large portion of eastern South Africa.
It is a medium-sized chocolate-brown bird, with a yellow beak, eye patch, feet and legs. The head, throat and tail are black, with the tail having white tips and white undertail feathers. The large white patches in the wings are noticeably visible when the bird is in flight. Mynas are very noisy birds and are often found in pairs or small groups where they spend a lot of time on the ground feeding. They are omnivorous. The largest proportion of the common myna’s diet consists of insects and other invertebrates. Ironically, mynas are now believed to destroy beneficial insects in some of the areas where they were originally introduced to reduce the numbers of pest insects. When insects are scarce, fruits and seeds make up a more important component of their diet. At such times, common mynas can become agricultural pests.
Mynas are aggressive and are thought to compete for the same resources as indigenous birds. They are also known to eat the eggs and attack the fledglings of other birds.
It is surprising, however, given the bird’s abundance in thousands of suburban gardens (and smallholdings) throughout the country that very few empirical studies have quantitatively assessed the effects that increasing myna populations are having on indigenous birds. (Peacock, van Rensburg, Robertson)
Are there any smallholders who have noticed an actual decline of any indigenous bird species on their plots where there is an increase in the myna population?
We’d love to hear from you.