Red-billed quelea (Quelea quelea) is the world's most abundant species of bird, with an estimated population size of 10 billion. It migrates around southern Africa in huge, cloud-like flocks and has a rather annoying habit of emptying whole fields in moments. Hundreds of millions of these birds have been killed in population control attempts, with no visible success at all.
A quick illustration for a blog post: black marker and digital coloring.