By The Numbers

Every wildlife reintroduction depends on numbers. The more animals you can release into the wild, the better the odds are that some will survive to breed. That is especially true for long-lived, slow to reproduce species like Whooping cranes. Since we moved to White River Marsh in 2011 it has been challenging to build up this population for a number of reasons.

Stochastic resilience is a term researchers use to describe the ability of a population to overcome the random occurrences that, from time-to-time, put pressure on the survival of a species.

This past spring is an example of the environmental pressure that both Whooping cranes and Sandhills had to tolerate. Above freezing temperatures in March allowed many cranes to begin nesting but a prolonged and heavy snowfall in April caused the abandonment of at least some of those nests. After the snow we were back to seasonal weather and the cranes started the second round of nesting – just in time for record rains to raise water levels and flood many nests throughout central Wisconsin.

We are currently studying the reproductive success in Sandhill cranes in hopes of determining how suitable this environment is for the Whooping cranes we are working so hard to reintroduce. At the same time we are releasing a few parent-reared Whooping cranes but the odds are stacked much higher for the latter.

So far, we have located a dozen or so Sandhill nests and radio-tagged a handful of chicks. We know there were more nests out there that we couldn’t locate but eventually the resulting chicks will get bigger and their parents will lead them out into the open where we will have another opportunity to add them to this study.

By comparison, there are only four potential Whooping crane pairs in the area that might have bred this year. We hoped that 5-12 and 67-15 (F) would nest somewhere close to the pen site but they are hard to see and often appear together or flying when they are tracked. Normally during incubation, one would be on the nest while the other is off foraging in a field nearby. It is possible cranes 4-13 and 10-15 (F) are nesting in Germania Marsh west of White River, but again, they are too deep in the wetland to see. Both of those females are only three years old so successful breeding would be an anomaly.

Whooping cranes 10-11 and 27-14 (F) nested at the Grand River Marsh, which is part of the White River complex. Their first nest was flooded out by the high water but they are nesting again and we have our fingers crossed. She is four years old so her chances or better but they are normally five or six before they are successful at producing a chick.

Numbers 4-12 and 3-14 (F), known locally as the Royal Couple, nested deep in the marsh this year. So deep in fact, that we can’t get in there to check on them or even see them from our live camera perched thirty feet in the air. They were last seen together foraging near the Crane Camera on May 3, and thereafter, only one-at-a-time was spotted foraging up until May 31st. Since then, we haven’t seen either of them in their favorite foraging field.

We have aerial shots of the nest and Bev Paulan was able to confirm two eggs. Heather predicted they would hatch on or around May 30th and we know they were still incubating, or possibly brooding, on May 27th. But by May 31st, the nest was empty and they were nowhere to be seen. 

One of the cranes is still on the nest in this image.

And in this photo – captured 4 days later the nest is empty.

It’s all very disappointing but to be expected. They are still young and need to learn by trial and error how to deal with predators, weather events and all the other threats that wildlife encounter daily.

All of these variables are considered when a population viability analysis (PVA) is done to predict whether a species will survive into the future. When there are lots of them around as in the case of Sandhills, the population can still grow, albeit slowly, went they endure a spring like this past one. But when the numbers are low like the four pairs of Whooping cranes around White River, a few losses make a big difference.

We must remember that this entire recovery effort started with only fifteen individuals and if nothing else, Whooping cranes are tenacious.  

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10 Comments

  1. Catherine Wohlfeil June 8, 2018 11:00 pm

    Has anyone tried building/providing raised nesting platforms which would be more difficult to approach by predators?

    • kat June 12, 2018 7:21 pm

      I am thinking it would have to be really raised, Catherine. I saw a fox sail over my deck railing from 10-12 feet from the ground and catch a squirrel. Then would the adult whoopers build in such an unusual setup, and would the little whoopers fall and hurt themselves getting out of the nest?

  2. Cheryl Murphy June 8, 2018 8:58 pm

    So many factors to deal with for the beautiful whooping cranes and for OM. We appreciate your efforts and continue to hope that some successes will come this year. And hoping the RC is OK along with the rest of the cranes. We are pulling for all of you!

  3. Dorothy N June 8, 2018 12:45 pm

    Thank you for the detailed description of the current status of our beloved whoopers. And ESPECIALLY for your commitment to these precious birds.

  4. Susan O’Connell June 8, 2018 12:05 pm

    I was wondering if anyone thought of using drones to check out areas too deep to venture into?

    • Joe Duff June 8, 2018 1:46 pm

      Thanks Susan but we are not allowed to fly drones over public lands. The FAA has authority over everything that flies and all of what is referred to as National Airspace, which means anything above the ground. They have divided it up into sections with varying restrictions like around airports and over important installations like military bases, power plants and prisons. Drones are not allowed to operate from public lands like refuges and wildlife areas but they can legally fly over them just like any airplane. However, we have a great relationship with the DNR and White River Marsh so we are not going to question their rules. Because there are so many drones these days, people are suspicious of them. Although it is perfectly legal to fly over private property, owners get upset as if we are trespassing. So to avoid alienating our neighbors, the drone we have has not been that useful.

  5. Richard P Brooks June 8, 2018 9:20 am

    Thanks for the update and all your work.to bring back an eastern migratory population. While you have not seen the RC has your radio van indicated if they are still out in the marsh?

    • Heather Ray June 8, 2018 9:46 am

      Unfortunately both of these cranes have non-functional transmitters so we must get visuals on them to know what they’re up to or where they are.

  6. kat June 8, 2018 9:14 am

    Everyone who loves the whooping cranes has to be incredibly tenacious. I admire and root for OM, which has done such tremendous work, often unfortunately recently having had additional difficulties added by the feds, etc. Please hang in there, the whoopers need you.