By Alan OwYong and Yong Ding Li.
Three species of African seed-eaters photographed in the grasslands of Punggol Barat (L to R): Orange-breasted Waxbill, a pair of Red Avadavats and the destructive pest bird, the Red-billed Quelea. Photo by Johnson Chua.
The massive population of the non-native Javan Myna (c. 300,000 to 1,000,000 individuals) in Singapore today is a reminder of the problems introduced birds can pose if their numbers are left unchecked. Such a situation resulted from an introduced species adapting well to our local environment. If the myna population were actively managed a couple of decades ago, they could be less of a headache today. In urban habitats, Javan Mynas have out-competed and displaced our native Common Mynas and to a lesser extent the Eurasian Tree Sparrows, besides being a public nuisance in our housing and shopping areas.
Over the past four years, we have also been seeing another influx of alien bird species into Singapore, especially seed-eaters such as finches and weavers native to Africa. This has coincided with the ban of importing birds from neighbouring countries affected by the bird flu. Before this restriction came into place, the most common species released during religious festivals was the Scaly-breasted Munia, a native of Southeast Asia.
The new alien species that we have observed flying around our open grasslands are mainly weavers, waxbills, mannikins, munias, whydahs, bishops, and widowbirds, mostly of African origin. We estimated that more than 25 species of these seed-eating birds have been reported flying free here in Singapore the last four years. The discovery of the Red-billed Quelea, a destructive pest bird in much of Africa in some parts of Singapore has red-flagged the danger introduced birds can cause.
While not all alien species are able to adapt to our local climate and habitats, we have observed that many of them have not only appeared to have settled in, but are breeding with varying degrees of success. The Golden-backed Weavers have been nesting for a couple of years in Lorong Halus and Tampines Eco Park. Likewise, we recorded the breeding of the Common and Red-rumped Waxbills in our northern parks. Others like the distinctive Long-tailed Whydahs have been photographed mating at the Punggol Barat grasslands. Potentially, these are the first signs of proliferation. Indeed, these aliens need to be monitored and if necessary, managed. More importantly, our native species may not be able to compete with the more aggressive new comers and may be in danger of suffering population declines. Our native Long-tailed Parakeets losing out to the introduced Red-breasted Parakeet is a case in point.
Furthermore, there are several issues concerning an alien replacing a native species: a) disruption to the ecological balance of our native ecosystems, b) outcompeting native species and eventually driving their extinctions, and c) acting as a channel for various diseases and zoonotics. Once established locally, alien species can even spread and cause ecological problems in neighbouring countries.
Given the many biodiversity and urban considerations, the Bird Group has written in to AVA (Agri-Food and Veterinary Authority of Singapore) to recommend restricting the importation of common seed eaters from Africa and other countries. Australia has already taken this step, and there is no reason for Singapore not to follow suit. AVA can simply administer a blanket ban, eliminating the need to list individual species, which can pose impediments to enforcement. Such seed-eating species are typically not kept as pet birds as they do not sing and have no special appeal. They are mainly sold for religious releases. The Bird Group does not recommend any substitute species as many of these (e.g. munias) may have to be wild caught. The mortality rate from the point of capture to transporting them to bird shops is very high and hence not tenable, besides depleting the wild populations of many species. The Bird Group has also offered to assist AVA by monitoring and conducting ad-hoc census of these non-native bird species in the field.
Reproduced from the Sept-Oct 2015 issue of the Nature News with permission from the Nature Society ( Singapore).