South America Invaded: European Starling

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The European, or common, starling Sturnus vulgaris is native to Eurasia, and migrates into north Africa to over-winter. It was intentionally introduced to North America, Australia, New Zealand and South Africa, mainly for aesthetic reasons but sometimes also to control insect pests – ironically, it is now considered a pest itself. More recently it has been introduced to South America, and there are fears that it will spread through much of the continent unless urgent action is taken.

Small beginnings

The starling is currently only found in a small part of Argentina, where it is known as the estornino pinto. It is thought to have been introduced to Buenos Aires in about 1987, and has now become established in the surrounding coastal zone, between Tigre and La Plata. The immediate priority is to prevent it spreading up the Rio de La Plata to the Parana Delta and neighbouring Entre Ríos province, renown for their rich biodiversity and high productivity. It is vital to take advantage of the opportunity to eradicate this invader from South America while it is in an early stage of its colonisation, and restricted to a limited area. The North American experience illustrates how quickly this invader can spread from a relatively small founder group introduced at a single point. The starling was first introduced to the United States in 1890, when 100 starlings were released in New York’s Central Park, apparently in the hope that all birds mentioned in Shakespeare’s works would become established in the New World. Today the starling is widely distributed across the United States and Canada, with a population estimated at about 200 million birds.

The species’ success as an invader can be attributed to the fact that it is a habitat generalist, able to exploit a wide variety of habitat types, nest sites and food sources. Its ability to co-exist with humans allows it to become established in agricultural fields, cities, sewage treatment facilities and garbage dumps.

Health hazard and agricultural pest

European starlings are highly colonial, gathering in flocks that may number in the thousands to feed, roost and migrate, although they tend to be solitary nesters. Their droppings cause sanitation problems in and around buildings, are corrosive to paint and plaster, and provide a growth medium for the fungus that causes the human respiratory disease histoplasmosis. The birds themselves carry diseases that may be transmitted to humans, and itch-causing mites in their feathers. Furthermore, large flocks of starlings close to airports pose a bird strike hazard to planes. European starlings also cause economic losses in agriculture. They are a potential threat to domestic animals, as they can transmit diseases by contaminating food and water sources at livestock and poultry facilities with their droppings.

They sometimes impact crop production by eating cultivated fruits, particularly berries and grapes, and by uprooting sprouting plants and eating sowed seed in grain fields. The birds have a negative affect on biodiversity, as they eat large quantities of insects, spiders, snails, earthworms, lizards and frogs, and compete with other birds for these resources. They also compete aggressively with indigenous hole-nesting birds for nest sites, often driving other birds from their nests, destroying eggs and killing nestlings. In addition, the birds cause secondary impacts on biodiversity by dispersing the seeds of invasive alien plants.

Control

In most invaded countries, there is no systematic attempt to control European starlings, and effort is focussed instead on mitigating their impact. For example, birds can be excluded from buildings by sealing up holes or covering them with strong netting, while commercially available repellents, coiled razor wire or spiked boards can be used to discourage roosting on ledges or roof beams. Strips of plastic or rubber hung in open doorways of farm buildings have been successful in keeping birds out, while allowing access to people, machinery and livestock. A variety of farm management practices may also be employed to limit food and water available to starlings, and hence make the livestock environment less attractive to them. Where cost-effective, netting can be used to protect fruit crops such as grapes and berries. Frightening is effective in dispersing starlings from roosts, small-scale fruit crops, and some other troublesome situations, including airports. However, poisoning with Starlicide is the only effective way to kill starlings. Poisoned birds experience a slow, non-violent death, usually dying 24 to 36 hours after feeding, often at their roost. Prebaiting (using a non-poisonous bait) should be conducted for a few days prior to poisoning, to accustom the birds to feeding on bait at a particular location.

Reference: Matthews S. & Brandt K.   South America Invaded: the growing danger of invasive alien species.  Global Invasive Species Programme 2006

   
 
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