Sandhill cranes may help solve puzzle of dwindling whooping crane population

Jan 28, 2013 | Corpus Christi Caller-Times by David Sikes | Related Press

BLESSING — They could have been a mile away, but they weren’t.

The powerful and distinctive call of sandhill cranes resembles the prolonged coo of a dove funneled through the rotating blades of a fan. And during flight, males and females alike announce their arrival long before we see them floating gracefully on wingspans that stretch more than six feet from tip to tip.

“Here they come,” my hunting partner Dave Phillips said prematurely from the edge of a field somewhere in Matagorda County.

We shrunk into the briers with shotguns. Some 40 yards away a half dozen realistic decoys with their beaks to the ground shook in the wind. Minutes passed.

“There they go,” Phillips lamented quietly as we watch a group of about a dozen wary sandhills wing their way across the plowed field that had served as their feeding grounds the previous day.

Predictability in nature often means death. And sandhills are among the best at dodging their demise, whether it be from hunters or natural threats. Fossils of sandhill cranes found in Nebraska suggest they were here 6 million years ago. This puts the sandhill as the oldest bird species still living today.

For all the similarities shared by sandhills and their endangered cousin, the whooping crane, survivability would barely make the list.

After dipping to 16 birds in the 1940s, North America’s only other crane has struggled with the help of man to boost the wild flock to about 300 birds, which split their time between Canada and Texas. Meanwhile six subspecies of sandhills — three in Texas — number more than 600,000, representing a successful rebound of their own. It is the world’s most abundant crane, though two nonmigratory subspecies of sandhills are still endangered.

The less flashy gray sandhill crane is slightly shorter than the iconic whooper, which stands a stately five feet tall in stark white plumage. Retired U.S. Fish & Wildlife biologist Tom Stehn, the longtime caretaker of the flock at the Aransas National Wildlife Refuge near Austwell, says this obvious difference in hideability most likely contributed to the whooping crane’s dwindling population.

It doesn’t help that unlike the sandhill, whoopers are extremely territorial year-round, which means they require much broader wetlands for breeding and during their time in South Texas. Diminishing wetlands threaten their future. The whoopers’ territorial nature also means they don’t enjoy safety in flocks like sandhills do when not breeding.

And their diets are different. Sandhills prefer grains, seeds, vegetation and bugs, and have adapted well to the expansion of agriculture along migration routes.

Whoopers are more carnivorous, preferring foods tied to wetlands, such as crabs, clams and aquatic invertebrates. Though they do like corn and wolfberries, whooping cranes are not as adaptive as their camouflaged relatives.

And yet the two cranes have much in common. Other than similar profiles they share the same migration routes where they spend time at the same watering holes, avoiding the same threats and being exposed to the same diseases and parasites. Perhaps something about the sandhill’s success is key to the whooping crane’s recovery.

Read the entire article »