(CNN) Madrid's city council is preparing a plan to clear the city of its pesky parrots -- which will include the "ethical slaughter" of the birds and and sterilization of eggs, authorities said Monday.

Argentine parrots -- myiopsitta monachus, also known as monk parakeets -- are native to South America, but many were kept as pets in Spain before ownership became illegal in 2011.

Many of the parrots escaped, or were released from captivity, and are now prolific in Madrid, as well as number of other areas in Spain. The population of Argentine parrots in Madrid's parks has risen by 33% in three years, from 9000 in 2016, to 12,000 already accounted for in 2019, according to data from the Spanish Society of Ornithology.

In 2005, there were an estimated 1,700 of the birds in Madrid.

As the population grows, so do the problems. The birds, considered an invasive species in Spain, are noisy, messy, and are certainly ruffling the feathers of local residents, who have already filed 197 complaints about the birds this year, and 209 in 2018.

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