They'd been on our planet for millions of years, but 2018 was the year several species officially vanished forever.

Three bird species went extinct last year, scientists said, two of which are songbirds from northeastern Brazil: The Cryptic Treehunter (Cichlocolaptes mazarbarnetti) and Alagoas Foliage-gleaner (Philydor novaesi), according to a report from the conservation group BirdLife International.

According to BirdLife, the other extinct bird is Hawaii's Po'ouli (Melamprosops phaeosoma), which has not been seen in the wild since 2004 (the same year the last captive bird died).

A disturbing trend is that mainland species are starting to go extinct, rather than island species: “Ninety percent of bird extinctions in recent centuries have been of species on islands,” said Stuart Butchart, BirdLife’s chief scientist and lead author on the paper.

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“However, our results confirm that there is a growing wave of extinctions sweeping across the continents, driven mainly by habitat loss and degradation from unsustainable agriculture and logging," he said.

An additional species of bird – the Spix’s macaw, which was made famous in the 2011 animated movie "Rio" – was declared extinct in the wild. Only a few dozen captive Spix's macaws are alive.

That species was wiped out in the wild because of deforestation and other factors such as the creation of a dam and trapping for wild trade.

A few other bird species that are near extinction have such exotic names as the New Caledonian Lorikeet and the Pernambuco Pygmy-owl.

Beyond birds, other animals such as the vaquita (a dolphin-like porpoise) and the northern white rhino are near the end.

"Vaquitas are the most endangered of the world’s marine mammals," the National Oceanic and Atmospheric Administration said. "Less than 30 vaquitas remain in the wild, and entanglement in gill nets is driving the species toward extinction."

The last male northern white rhino died at a wildlife sanctuary in Kenya in 2017, Mashable reported. Only two females are left.

In the USA, just a few dozen endangered red wolves remain in the wild, and the population could go extinct within eight years, according to a report released in 2018 by the U.S. Fish and Wildlife Service.

Earth "is now in the midst of its sixth mass extinction of plants and animals – the sixth wave of extinctions in the past half-billion years," according to the Center for Biological Diversity.

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The group said, "We're currently experiencing the worst spate of species die-offs since the loss of the dinosaurs 65 million years ago.

"Although extinction is a natural phenomenon, it occurs at a natural 'background' rate of about one to five species per year. Scientists estimate we're now losing species at 1,000 to 10,000 times the background rate."

In the past 500 years, the center estimates that about 1,000 species have gone extinct, from the woodland bison of West Virginia and Arizona's Merriam's elk to the Rocky Mountain grasshopper, passenger pigeon and Puerto Rico's Culebra parrot.