Sandhill cranes haven't changed much in millions of years. They're still nearly identical to fossils of their ancestors from the Pliocene Epoch, making them one of Earth's oldest surviving bird species.

They're also the most abundant cranes alive today, with about 650,000 spread widely across North America and extending as far as Cuba and Siberia. Yet despite all their success, even venerable wildlife like sandhill cranes are still sometimes caught off-guard by Mother Nature's curveballs.

A few of those moments are now comically — but also beautifully — immortalized thanks to Tara Tanaka, a Florida nature photographer who filmed sandhill cranes during a recent trip to Bosque del Apache National Wildlife Refuge in New Mexico. Tanaka recorded two subspecies, lesser and greater sandhill cranes, as they struggled to walk or even stand on thinly frozen ponds in the refuge.

"[T]here were many mornings that the ponds had ice, making mornings challenging for many of the cranes," Tanaka writes on Vimeo, although she points out that some birds had more trouble with the ice than others. "In one clip you can see that in these conditions, the lighter Lesser Sandhill had the advantage over the heavier cousin, the Greater Sandhill. I hope it brings a smile to your face."

There are six subspecies of sandhill crane, three of which endure long southern migrations to warmer wintering grounds. Lesser sandhills are the smallest at about 6 pounds and 3 feet tall, while greater sandhills can grow up to 14 pounds and reach 5 feet in height. They mate for life, and are famous for elaborate mating dances that involve wing flapping, bowing, leaping and tossing of grass or sticks. About 500,000 migratory sandhills converge on a 75-mile stretch of the Platte River every year during their spring migration, representing nearly 80 percent of the entire species.

sandhill cranes mating dance

Two sandhill cranes perform a courtship dance in New Mexico. (Photo: U.S. Fish and Wildlife Service)

While sandhill cranes are doing well overall, they aren't immune to the threats people often pose for wetland wildlife. The greater sandhill crane was devastated by unregulated hunting and habitat loss last century, for example, leading to severe population declines. It has begun to recover in recent decades thanks to conservation efforts, but some of its eastern relatives aren't as lucky. Three non-migratory subspecies are endangered in Mississippi, Florida and Cuba, where they must compete with residential and commercial development for dwindling patches of habitat.

Sandhill cranes are survivors, though, as millions of years of history can attest. With many populations now increasing — and a "Least Concern" listing from the International Union for Conservation of Nature — there's reason to be optimistic that these ancient birds are on thin ice only in a literal sense.

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.