A NextGen Blog post by Johanna Mitra, Stony Brook University.
All Photos © Alison M. Jones, unless otherwise noted.
This is the latest post to our NWNL NEXTGEN BLOG series. Since 2007, NWNL has supported watershed education with college internships and blogging opportunities. This NWNL NEXTGEN BLOG series posts students’ essays; sponsors a forum for our student contributors; and invites upper-level students to propose work focused on watershed values, threats and solutions.
Johanna Mitra is currently an undergraduate student at Stony Brook University. She is majoring in ecosystems and human impacts on them, with a focus on wildlife conservation. She is minoring in geospatial science. This is the final part in her 4-blog series on migratory birds and the “Flyways of the Americas” that follow our NWNL case study watersheds.
As the last post in this “Flyway of the Americas” series, this blog covers the Central Flyway, a migratory corridor stretching one million square miles across the Great Plains, the Rocky Mountains, and all the way down to the Gulf Coast.[mfn]Ducks Unlimited[/mfn] Each year, its rivers and wetlands host as many as 380 species of migratory birds as they travel between their breeding and wintering grounds.[mfn]Bird Life International[/mfn] Nebraska’s Platte River, a tributary flowing from the Colorado and Wyoming Rocky Mountains across the Great Plains to the Missouri River, is directly within the Central Flyway. Every spring, it is the home to “one of the great mass migrations on the planet,” as half a million sandhill cranes arrive there to rest and feed before continuing their migration northward.[mfn]Rosen, Jonathan[/mfn]
In 2017, NWNL led an expedition to the Lower Platte River Basin to document this migration and explore how sandhill cranes, like other species in the region, depend on the river’s resources. During the course of the expedition, NWNL heard about research and birding experiences from Dr. George Archibald, a leading expert in cranes and co-founder of the International Crane Foundation, as well as Brice Krohn, President of Crane Trust. As the Platte River prepares for a busy 2021 migration season, it’s important to understand just how vital this river is to the Central Flyway and the birds that use it.
What makes the Platte River the ideal migratory stopover?
Known as the river that is “a mile wide and an inch deep,” the Platte’s braided riverbed creates the ideal “staging area,” or mid-migration rest-stop. By keeping to the Platte’s shallow waters at night, sandhill cranes can avoid predators. In the morning, the adjacent wetlands and nearby croplands offer ample opportunity for feeding.[mfn]National Wildlife Federation[/mfn] Because the many birds that stop here during migration season have already traveled hundreds of miles and likely will travel hundreds more, access to food is a top priority. By feeding on leftover corn from the fall harvest, sandhill cranes are able to gain an additional 20% of their body weight, enough to fuel them the rest of their way up north.[mfn]Miller, Matthew L.[/mfn]
The sandhill cranes that come to the Platte River every year make up 80% of the total sandhill crane population in the world; but they’re not the only crane species to use the Central Flyway.[mfn]Miller, Matthew L.[/mfn] In his 2017 lecture at the Crane Trust, Dr. George Archibald explained that North America’s only other crane species, the endangered whooping crane, also makes a rare appearance in this river basin. Archibald states that what was once a population of only 15 whooping cranes in 1940 has now increased to about 350 individuals, all of which fly through Nebraska at some point during the migration season.[mfn]Archibald, George[/mfn]
Other endangered and threatened bird species utilize the Platte River too. Interior least terns and piping plovers nest on the river’s sandbars and shoreline. The more sedentary greater prairie chickens roam the river basin’s grasslands, performing their unusual and thumping mating dances at the same time as the crane migration.[mfn]National Wildlife Federation[/mfn]
Threats to the Platte River and Sandhill Crane Migration
Unfortunately, today’s Platte River habitat is only a fraction of its original size. Over time, the construction of dams and reservoirs along its 310 miles has altered its flow and the river basin itself.[mfn]Buckley, Emma Brinley[/mfn] The staging area for sandhill cranes used to be around 200 miles long; but it’s a very different story today.[mfn]Rosen, Jonathan[/mfn] During Brice Krohn’s interview with NWNL, he recalled how much wider the river was when he visited as a young boy: “It was 80 miles wide here at its chokepoint, but now their flyway is only 50 miles wide.”[mfn]Krohn, Brice[/mfn] Dr. Archibald also mentioned that “one of the great dangers to the sandhill cranes is if we lose the water of the Platte River.” This is a growing threat, as climate change alters precipitation patterns in the region.[mfn]Archibald, George.[/mfn] Since human activity and infrastructure have already significantly impacted the river’s flow, Dr. Archibald considers it “extremely important to make sure that the Platte River continues running.”[mfn]Archibald, George.[/mfn]
Also due to climate change, there is concern that the sandhill cranes will lose their main food source in this river basin – waste corn. As temperatures continue to rise and droughts in corn-growing regions become more frequent, corn yields will decline and farmers run a higher risk of “bad crop years”.[mfn]Harvey, Chelsea[/mfn] This translates into less waste corn at the end of the season. As a result, farmers might be prompted to grow alternate crops that fare better in the changing climate. Dr. Archibald believed “Should there be a change in agricultural practices, the food that cranes depend upon may be gone tomorrow.”[mfn]Archibald, George[/mfn]
The sheer number of cranes feeding on farmland can also cause conflict with the farmers themselves, especially when the birds begin tearing up planted crops and eating growing corn seedlings instead of waste corn. To combat crop destruction, the International Crane Foundation developed a non-lethal and non-toxic product called “Avipel”, designed to deter the sandhill cranes from feasting on new seedlings.[mfn]Beilfuss, Rich[/mfn]
The scale of the sandhill crane population in the Platte River each year is a sure sign of the region’s resiliency. Crane Trust’s rough estimates for 2017 were of 600,000 sandhill cranes, which increased to 700,000 in 2018. More recent population estimates made using survey data from the Crane Trust and other agencies suggest that at the peak of 2019’s spring migration, there could have been as many as 1.27 million sandhill cranes in the Central and North Platte River Valley combined.[mfn]Caven, Andrew[/mfn] You can follow the Crane Trust’s annual sandhill crane count for 2021 on their continuously-updated website.
With the help of dedicated organizations like the Crane Trust and International Crane Foundation, the Platte River will remain the site of one of the greatest migrations in the world. Tourist visits during this migration are an important element of fiscal support for these two organizations.
The Future of the Flyways of the Americas
Each year, billions of birds rely on the rivers of all four flyways – the Atlantic, Mississippi, Central and Pacific – and their associated wetlands and streams; yet these waterways face mounting pressure from human activity and climate change. As a new US Administration steps into office, indications are that watershed conservation may become a greater priority, as it recognizes the invaluable role of migratory birds in our economy, culture and environment. In describing the sandhill crane migration, Brice Krohn said, “Even if folks aren’t really into birds, the sheer spectacle of their migration is very special.”[mfn]Krohn, Brice[/mfn] This sentiment is true of migrations across all the world’s flyways. It’s a truly amazing feat of endurance that wouldn’t be possible without our freshwater resources.
Archibald, George. “Lecture at the Crane Trust & Visitor Center.” NWNL Expedition at the Crane Trust, March 22, 2017. Accessed on Feb 9, 2021 by JM. https://nowater-nolife.org/george-archibald-on-cranes/
Beilfuss, Rich. “Notes from the President – See a Sandhill? Thank a Farmer!” International Crane Foundation, July 6, 2020. Accessed on Feb 9, 2021 by JM. https://www.savingcranes.org/notes-from-the-president-see-a-sandhill-thank-a-farmer/
Buckley, Emma Brinley. “Platte River Timelapse.” NWNL Expedition at the Crane Trust, March 21, 2017. Accessed on Feb 8, 2021 by JM. https://nowater-nolife.org/platte-river-in-timelapse/
Caven, Andrew. “Sandhill Crane Counts 2020 – Week 5.” The Crane Trust, March 12, 2020. Accessed on Feb 15, 2021 by JM. https://cranetrust.org/news-events/the-prairie-pulse.html/article/2020/03/12/sandhill-crane-counts-2020-week-5
“Central Americas Flyway.” Bird Life International, n.d. Accessed on Feb 7, 2021 by JM. http://datazone.birdlife.org/userfiles/file/sowb/flyways/2_Central_Americas_Factsheet.pdf
“DU Projects: Central Flyway.” Ducks Unlimited, n.d. Accessed on February 6, 2021 by JM. https://www.ducks.org/conservation/where-ducks-unlimited-works/waterfowl-migration-flyways/du-projects-central-flyway
Harvey, Chelsea. “Rising Temperatures Could Cut Corn Production.” Scientific American, June 12, 2018. Accessed on Feb 15, 2021 by JM. https://www.scientificamerican.com/article/rising-temperatures-could-cut-corn-production/
Krohn, Brice. Interview for NWNL Expedition at the Crane Trust, March 24, 2017. Accessed on Feb 9, 2021 by JM. https://nowater-nolife.org/central-platte-river-basin/
Miller, Matthew L. “Platte River Sandhill Cranes: Enjoying North America’s Greatest Bird Spectacle.” The Nature Conservancy, March 3, 2014. Accessed on Feb 8, 2021 by JM. https://blog.nature.org/science/2014/03/03/platte-river-nebraska-sandhill-cranes-birding/https://blog.nature.org/science/2014/03/03/platte-river-nebraska-sandhill-cranes-birding/
“Platte River.” National Wildlife Federation, n.d. Accessed on Feb 8, 2021 by JM. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Wild-Places/Platte-River
Rosen, Jonathan. “Cranes on the Platte River.” National Audubon Society, February 2013. Accessed on February 7, 2021 by JM. https://www.audubon.org/magazine/january-february-2013/cranes-platte-river