How The Cattle Egret Is Gradually Overpopulating Parts Of Brazil
It came, it saw, and it conquered. Not the romans, but the cattle egret (Bubulcus ibis), an invasive bird species with great capacity to invade and occupy new areas in different parts of the world. In recent years it has proliferated in the Americas, especially Brazil. Invasive species are a growing global problem as they have great survival rates and often become a threat to the local populations. A new study published in the open access journal NeoBiota attempts to understand how the cattle egret invaded the New World, and the damage caused by it to indigenous bird species.
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The cattle egret is a type of heron found in tropics, subtropics, and warm temperate zones. It is originally native to Africa, southern Europe, and western Asia and often found near grasslands, farmlands, or rice paddies accompanying cattle or other large mammals. Most invasive species are introduced to an environment as a consequence of some human activity. But not in the case of the cattle egret, which seem to have colonized and spread without any human help.
Cattle egret was first observed in the South American coastal country of Suriname between 1877 and 1882, followed by sightings in British Guiana and Colombia, and subsequently expanding throughout the Americas. In Brazil it was first sighted in 1964, feeding along with buffalos on Marajo Island, located at the mouth of the Amazon River in the state of Para.
Invasive species often have the genetic makeup that allows them to survive better than the locals. Better ability to survive in adverse conditions, better reproducing rates, and such. Though populations of cattle egret have not yet reached such levels that they are a threat to the native Brazilian fauna, they have caused a lot of damage to other island environments, such as the Fernando de Noronha Archipelago, which is 345 kilometers from the northeastern Brazilian coast. Since its arrival on the island in the 1980s, its populations have increased dramatically. The cattle egret drives adult native seabirds away from their nests in breeding colonies and predates the Noronha skink, which is endemic to the archipelago and is also under threat of extinction.
This study of cattle egret occupation of Brazil is a classic example of how invasive species adapt to new surroundings, their interaction with local species, and their seemingly predisposed ability to adapt to change in climate, which even the locals cannot survive. But studying the cattle egret in Brazil is a challenge to the researchers due to insufficient data on entrance time, locality, and number of events that facilitated its expansion. Nevertheless, their impact on native birds must be studied to maintain this delicate ecological balance.
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