Yellow-legged Gull

The dominant bird of the island by sheer number, forming one of Europe's largest colonies. It exploded from about 5,000 pairs in 1983 to some 45,000 individuals by 1994, fuelled by easy feeding at coastal landfills and fishing ports. That overpopulation harms the island, over-nitrifying the soil, killing the endemic thrift and preying on lizards and other seabirds' chicks, so adults and clutches have been culled since 1994, bringing numbers back to roughly 13,150 by 2013. Berlenga-ringed juveniles have turned up in the UK, France, Spain and Morocco.