This article originally appeared in Mongabay.
Eight Socorro dove chicks hatched at Chester Zoo in the UK this year. These brown floofs represent a significant milestone for a species that is extinct in the wild.
Socorro doves (Zenaida graysoni) once lived on Socorro Island, located 400 kilometers (250 miles) southwest of Mexico’s Baja California coast. Old reports describe birds that walked right through human camps and over people’s boots without fear. This friendly behavior would later cost them their lives.
The trouble started when sheep arrived in the 1800s and ate the plants the doves needed. A naval base built in 1957 brought the final blow.
“Navy staff and their families brought house cats which became wild and caused terrible damage to the native wildlife, including the Socorro dove population, which was last seen in the wild in 1972,” Andrew Owen, head of Chester Zoo’s bird department, said in a statement.
The feral cats hunted these trusting birds with deadly effect. Scientists who searched the island in 1978 and 1981 found no doves left.
The species only survived because of quick thinking almost a century ago. In 1925, a California Academy of Sciences expedition took 17 Socorro doves back to the U.S. Every dove alive today comes from those birds.
Today, all of the known remaining birds live in zoos across North America and Europe. About 200 birds make up the entire surviving population, according to Chester Zoo staff.
The size of the population poses a problem. When a population starts with only a few animals, their offspring can experience health issues due to inbreeding. The birds also lose genetic variety that helps them fight diseases.
Socorro doves exhibit some unique behaviors among dove species. Instead of living in groups, they prefer to be alone or in pairs, and the male birds are especially good fathers.
“The females will raise their chicks for a while and then get ready to mate again, so they’ll start a new nest of eggs before the first babies can fly,” said Clare Rafe, who helps manage birds at Chester Zoo. “When that happens, the fathers take over with the older chicks, feeding them and caring for them.”
This busy parenting style made sense on Socorro Island, where birds had only two to three months between storms and heat waves to raise their chicks.
“The hatching of eight new Socorro doves really is news worth celebrating,” Donal Smith, a researcher at Monash University in Australia, told Mongabay. “It’s a miracle that this species gave extinction the slip and is still with us, and institutions like Chester Zoo play such an important role in being custodians of these precious birds that exist nowhere else on Earth.”
He added that a healthy population, boosted by these eight new squabs, “will be a critical foundation for efforts to return this species to the wild.”
Socorro Island looks much better now than when the doves disappeared. All the sheep were removed by 2010, and special bird houses, built in 2005, await the doves’ return.
“Now, the sheep are gone from Socorro. So maybe there will be a reintroduction,” Smith suggested. “I think that’s a really interesting case partly because it’s been such a long time. But also the chance for recovery, which I think is real.”
But big challenges remain. Cats still run wild on the island, and researchers must deal with changes that have happened during the 50 years since the doves left their home.
Each baby that survives makes the population stronger for the future. Some chicks have grown up completely, and more eggs might hatch this season.
The Chester Zoo chicks are showing real progress. “It is a big deal,” Rafe says. “We have several chicks which have successfully become independent, and the others are close to being able to fly.
“They might look quite plain and brown from a distance, but they have what looks like shimmery blusher on their heads,” Rafe added. “They have big personalities, too, with the males being a bit aggro — they certainly aren’t peace doves!”
Socorro doves belong to a special group: at least 33 animal species that have disappeared from the wild and only survive in human care, according to a 2023 study. Since 1950, 11 such species have gone extinct, while 12 have successfully been returned to the wild, including the European bison (Bison bonasus), which now live freely across Eastern Europe.
“Without the important work zoos do, these species would be lost forever,” Owen said. “Our job at Chester Zoo is helping to keep the population alive and hopefully, someday our birds will support the work done by other organizations, and their babies will see Socorro Island.”
