A bird introduced to the Cook Islands to control a coconut pest eventually became an unwanted species itself. In 1915, the common myna was brought to the islands to control the coconut stick-insect, a major pest affecting coconut palms. The bird was initially viewed as a biological control agent.It later spread across multiple islands and began competing aggressively with native birds, raiding crops and invading human settlements. According to the review published in npj Biodiversity titled ‘Society’s struggle with unwanted species: what centuries of history reveal about species bounty programs‘, the case is one example of how species introduced to control other pests can later become targets of control themselves.
Why were common mynas introduced to the Cook Islands
The common myna was introduced to the Cook Islands in 1915 for a specific purpose. The bird was brought in to control the coconut stick-insect, which was described in the review as a major pest affecting coconut palms. The introduction made the myna a biological control agent.At the time, the myna was therefore considered useful because of its role in controlling another unwanted species. However, its introduction did not remain limited to that original purpose. The birds spread across multiple islands. Their growing presence eventually created ecological and economic problems that changed their status from a useful control species to an unwanted one.
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How did the birds become a problem
After their introduction, common mynas spread across multiple islands in the Cook Islands. The birds began competing aggressively with native birds and also raided crops. They invaded human settlements as well, creating problems beyond the pest-control role for which they were introduced.These effects meant the myna was no longer viewed only as a biological control agent. Its presence was now linked to ecological and economic harm. The change was significant because the same species brought in to control one pest had itself become a species that people wanted to control.
A bounty programme was introduced to reduce myna numbers
The problems caused by common mynas eventually led to a bounty programme on Atiu Island. The review doesn’t describe how the programme worked. By 2014, nearly 13,000 common mynas had been trapped on the island according to a 2014 ABC News report cited by the review.Atiu Island became an example of a place where an intentionally introduced species later became the target of a programme designed to reduce its population after it was associated with ecological and economic harm.
Bounty programmes have targeted hundreds of unwanted species
The researchers identified at least 283 species across 449 species-country programmes in 60 countries over the past eight centuries. These programmes have targeted mammals, birds, fish, plants, reptiles, mollusks, insects, amphibians and crustaceans. The review found that bounty programmes have been launched for economic, ecological, and social (human health) reasons.It also found that some programmes had unintended consequences, including the removal of non-target species and effects that may inadvertently benefit target species, though these are not universal. The myna was introduced for biological control in 1915 before becoming the subject of a bounty programme on Atiu Island.