Size does matter: Scientists fascinated by talons, tracheas and body mass of sandhill cranes

Nov. 13—Velociraptor talons. Curled tracheas, which help produce a bugle that can be heard two miles away. A wingspan that can span 6 feet.

The sandhill crane is a symbol of changing seasons in New Mexico, and the scientific questions left to be answered about the bird are nearly boundless.

Crane questions

Ethan Gyllenhaal pulled out a drawer of sandhill crane specimens recently. Feathered bodies are kept in drawers and skeletal feet with velociraptor shaped talons are pinned on boards at the University of New Mexico's Museum of Southwestern Biology.

"There's three different subspecies that occur here in the Middle Rio Grande Valley that all spend the winter together. There's a really large one, the greater sandhill crane, and there's a very small one, the lesser sandhill crane," said Chauncey Gadek, a doctoral student studying the crane size evolution. "There's also an intermediate."

In the past 12 years, researchers at UNM have been trying to figure out what drives or constrains the dramatic difference in body size across the species, Gadek said.

The greater sandhill cranes fly south from colder climes like Utah, Colorado, Wyoming and southern Canada. The lesser sandhill cranes make longer journeys, traveling from northern Canada, Alaska and eastern Russia.

"There's a drastic difference in the migratory length, and we think that that's probably driving these body size differences, because the longer you have to migrate, it's less beneficial to be a lot bigger, because you'd have to generate energy to carry that larger body," Gadek said.

Researchers haven't determined definitively if the intermediate size is a separate subspecies or a result of hybridization between the greater and lesser cranes, Gyllenhaal said, but it's one question of many they'd like to answer.

Gadek also is studying the microbiome of crane lungs, which could help in understanding the transportation of fungal pathogens. Undergraduate biology major Brenda Ramos is studying avian malaria parasites in cranes, trying to see the difference in prevalence of parasites between the greater and lesser sandhills.

Gyllenhaal is a doctoral candidate who uses the museum's collection of more than 200 crane claws to find out if a difference exists between the greater and lesser sandhills.

"Cranes have this cool velociraptor claw that no one's really described much before," Gyllenhaal said. "It's convergent with a lot of other avian and non-avian dinosaurs, including velociraptor. They all have the same digit, that second digit gets what's called hypertrophied or raptorialized, where it's longer and more pointed."

Gyllenhaal takes photos of the crane claws, then uses a computer program to compare the curvature and length of the claws.

"That's all possible through this huge dataset, which is from this hunter salvage effort," he said.

Help from huntersThe UNM researchers go to the Bernardo Sandhill Crane Check Station and offer to fillet the hunters' catches in exchange for the carcass. Cranes are sometimes called the 'ribeye of the sky,' and hunters typically keep the breast meat to cook and eat.

"They're oftentimes thrilled at it, because most want their hunt to be used more than they can," Gyllenhaal said.

Along with dinosaur-like talons, cranes also have an elongated trachea that curves in and around behind the sternum.

"Having a longer trachea can make you sound larger than you necessarily are, so there's been a lot of theory to work out around why some birds have these coiled tracheas," Gadek said.

Bird watchingYou don't have to be a scientist to enjoy studying the majesty of sandhill cranes. Bird watching is seeing a renaissance in Albuquerque, said Bill Pentler, visitor services supervisor for the Albuquerque Open Spaces Division. And with food or a birdbath, even backyard bird watching can be rewarding.

Sandhill cranes are believed to be one of the oldest bird species in existence.

"Which means that when you hear that rattling call, you're hearing something almost prehistoric," Pentler said.

Cranes are "without a doubt one of the most, if not the most majestic of the bird visitors that we have in the Middle Rio Grande," Richard Shackley said.

Early in the morning, before the cranes have taken flight, Shackley and his wife hike in Albuquerque's bosque and can hear the cranes resting on sandbars in the river. The couple lead a bosque nature hike on the first Saturday of the month for the Open Spaces Division.

"We have people that have come on the hike that have lived two miles away from where we hike," Shackley said, "and they never realized there were trails there or that it was a state park or that there are open spaces for them to come out to enjoy any time they want."

One of his favorite spots for watching cranes is the stretch of the bosque between Alameda and Interstate 40.

"There are over 200 species of birds that inhabit the bosque here in Albuquerque and some of those are visitors throughout the year, such as the cranes, the turkey vultures, the hummingbirds, and others are here year round," Shackley said.

By December, as many as 10,000 cranes may descend upon the Middle Rio Grande Valley, said Amanda Walker, Bosque del Apache park ranger.

People can often empathize with cranes, Walker said. Cranes embark on a long journey to winter in the Land of Enchantment, much like the Bosque del Apache visitors who may travel from states away to witness the birds en masse. The cranes also travel in recognizable family units: adult birds with their babies, close to the size of the adults but with no adult plumage — making them easy to recognize.

The dates when the sandhill cranes arrive in the Middle Rio Grande Valley have shifted slightly over the past five to 10 years, Walker said. In years past, there would likely be hundreds of cranes in the Bosque del Apache by mid-October. Now, there are a few dozen in mid-October, with hundreds by the end of the month.

"That seems to be related to what food or water is available along their migration route. If there's food or water available in southern Colorado, the cranes, ducks and geese are unlikely to risk traveling further south if they're happy where they are," Walker said.

On the other hand, Pentler recalls one year the cranes flocked to Albuquerque in September, driven south early because of a drought in Colorado that limited the food supply.

"The cranes represent changing seasons, and if we pay attention to them we can learn a lot," said Dionne Epps, volunteer coordinator for Albuquerque's Open Space Visitor Center.

"And that's why so many of our volunteers love them so much, because they represent change."