Ask the Experts: Backpack Transmitters &; Genetic Bottlenecks

Last week I posted a second report about the Ask the Experts live online chat all about whooping cranes – a chat that the Wisconsin DNR held on Oct. 31st; and I wrote that I would post again soon about other topics that came up in the one-hour Ask the Experts program.

This is the third and final Ask the Experts post. There are links to connect to the first two – about the current migration season, the 2014 nesting season, and whoopers in Louisiana – at the end of this post. The transcript of the whole chat is online at the DNR website (select the link from the “Completed Events” box on the right side of the screen).

The experts hosting the chat were Davin Lopez, whooping crane coordinator for the DNR, Heather Ray, associate director of development for Operation Migration, and the International Crane Foundation’s Eva Szyszkoski (field tracking manager) and Sara Gavney Moore (communications specialist).

Backpacks? On Birds?

If the words above surprise you, you’re not alone. I was surprised to learn that small packs – holding smaller still cellular transmitters – that can be attached to birds by a single teflon ribbon are proving to be of help to the study of, and tracking of many avian species. They’ve been used with the snowy owls that are frequent winter visitors all over the northern U.S. They have also been used by the International Crane Foundation on released sandhill cranes and with ICF’s captive whooping cranes. There is hope that backpack transmitters might develop into a cost-effective answer for the Whooping Crane Eastern Partnership’s need to keep track of 100 wild whooping cranes in Wisconsin and all along the migration route. Currently WCEP uses very expensive satellite transmitters on some of the birds, and not-so-effective radio transmitters that can only reveal the location of a bird if it’s very close.

WCEP seeks to track all of its whooping cranes – 100 in the Eastern Migratory Population and 27 in Louisiana; very challenging once they are released into the wild.
(Photo from Wikimedia Commons)

So Operation Migration was asked to fit 3 of their ultralight-trained chicks with the transmitters and backpacks, to see how it would go; and also to compare the flight performance of those fitted with backpacks to the 4 who were without them. OM Pilot Joe Duff wrote all about this at the Field Journal in September, explaining the limitations of the current tracking devices and the hopes for a better answer; and the pros and cons of experimenting with the ultralight chicks. “In the end,” he said, “if we don’t try, we won’t learn anything.”

What they learned soon enough – after four or five attempted training sessions – is that the young whoopers with the backpacks were unwilling to follow the airplane for “more than a few hundred yards from the pen.” The problem, as described by Duff, was this: “they seem to disrupt the airflow over the bird’s back. That pulls the feathers up destroying the lift as well as creating drag.”

At Ask the Experts chat OM’s Heather Ray responded to a question about the backpacks being too heavy for the ultralight-trained whoopers. They aren’t “too heavy, as much as they disrupted the laminar airflow over their backs while in flight,” she responded, also noting that they have been used successfully “on many other species, i.e. Snowy owls and Sandhill cranes.

Another chat guest wondered about ” . . . plans to try the backpacks on adult whoopers? Their flight profile would be somewhat different from the colts – more gliding than flap-flight.” Davin Lopez responded that there have been discussions about that, “but for now the plans are to continue using them on sandhills and carefully observing them in flight for any issues.”

There was a question about how many of the birds in this Eastern Migratory Population have functioning transmitters, allowing them to be tracked. “About 60 birds,” said Eva. “We do post monthly updates that include maps showing the birds’ general location on the Whooping Crane Eastern Partnership’s website.

I asked how tracking is done during migration, wondering how it’s even possible to try to follow all the adult cranes up and down the migration route. “We try to check birds 2-3 times a week,” Eva responded, “and rely heavily on outside reports and cooperators for information. We get aerial support for surveys from the DNR and Windway Aviation, including a couple of tracking flights down the migration route.”

Another asked if all the DNR agencies in all the states along the Eastern Migratory route were capable and willing to help track the cranes. Not all other agencies have tracking equipment, Eva answered, but “we do have DNR assistance in a number of the states.”

So, that’s what’s new about tracking the EMP cranes. Now, for a brief look at how important the right genes are to the survival of the species.

What is the Genetic Bottleneck?

This is an issue that’s rather straight forward – easy enough to understand, and explain to others. But just think of the myriad challenging details for those whose job it is to oversee genetic diversity among the world’s whooping cranes.

Here’s the easy part: because the number of whooping cranes in the entire world dropped to only 21 individual birds in 1941 – there were 15 in the Aransas-Wood Buffalo population, and 6 more in the remnants of a flock in Louisiana – each one of the approximately 600 whooping cranes in existence today is descended from that tiny handful of ancestor cranes. Thus, there is only a minimal amount of genetic diversity protecting them.

Whooping crane pairs in captive populations are carefully matched with the goal of genetic diversity driving the decision. This
pair was photographed at the International Crane Foundation, by Joel Trick, used courtesy of WCEP.

The Experts were asked to explain more about it in two questions: “How many generations (or years or broods) might it take before natural genetic mutation occurs and the bottleneck “changes shape?” There is no certainty about how long that might take, Davin responded, “but since they are long-lived birds with slow reproductive rates it would likely take a long time.”

Another asked if he would “expand on natural genetic mutation and the “bottleneck?” Davin said: “All the whoopers in existence are from a very low number of distinct genetic profiles (a bottleneck), over time, genes mutate naturally creating new profiles that diversify the gene pool, and potentially increase the resilience of a population.”

And Eva offered a document online at ICF “that talks about genetic drift.” If you take a look at that document, you might think at first that it’s a job posting – for a “Species Survival Plan Coordinator,” but don’t be fooled by that. It’s really a 10-page “workbook” – part Genetics 101 and part Genetics for Endangered Species. Among other things it describes a multitude of factors that curators of captive populations must consider when playing the matchmaker for a pair of whooping cranes; the goal is always to pass on more genetic diversity to the next generation.

Although this concludes my writing about the Ask the Experts program, I’m sure it won’t be the last post to quote from things that I’ve learned there.

More from Ask The Experts:

All About Ultralight Migration   and    The EMP Nesting Season & Louisiana’s New Whoopers