SPRING CRANE MIGRATION, NEW CRANE RADAR FEATURES, AND INSPIRING STUDENT PROJECTS
From the desk of Prof. Koen de Koning: Latest news & insights
A Look Back at the Spring Migration
Screenshot of the Crane Radar on February 19, 2025
While small groups of cranes are still flying over our country in drips and drabs, we reflect on the spring migration of 2025. This migration is marked by a relatively early peak compared to previous years. As expected, the migration peaked on February 19, 20, and 21, thanks to pleasant spring temperatures, clear skies, and strong tailwinds. Ideal conditions for cranes to head north in large numbers. The peak, according to waarneming.nl, occurred on February 21, with more than 1,000 crane sightings.
How does this compare to previous years? In the past, there have clearly been leaner years for cranes over the Netherlands. So, this was a relatively good year. On the other hand, there have been years where more than 2,000 crane sightings were recorded at the peak! Additionally, it's noteworthy that the wind direction (southeast) at the peak of the migration was very favorable for cranes, passing more over the center of the Netherlands – along the Tilburg, Den Bosch, Arnhem-Nijmegen, and Enschede route. Yet, most cranes ultimately chose a route much further southeast – over the Belgian Ardennes and the German Eifel, meaning most sightings remained limited to (southern) Limburg. In other years, under similar conditions, many more cranes would have flown over the Netherlands. Where have all these cranes gone?
Part of the explanation lies in the fact that most cranes likely passed through during the night at the peak. Under favorable conditions, especially in spring, cranes tend to fly through the night. And the conditions were not only favorable here; in fact, the weather conditions along the entire route from Spain to northern Germany were favorable for cranes to continue flying through the night. As a result, cranes were observed at different times than usual along the entire route. Our cranes, therefore, left much further south than usual on favorable days, meaning they likely flew over us in the dark hours. Occasionally, groups did land, which meant small groups of cranes were visible across the country every morning, and they could also be tracked on the Crane Radar. However, the majority likely passed by unnoticed.
Another explanation is that we simply still don’t know enough about why cranes choose specific routes, and why this sometimes results in many sightings over the Netherlands, while at other times the mass migration passes by unnoticed. We do know that wind can have a significant effect on the flight direction (and thus the routes flown), and even more so on the flight speed (more scientific background on this via this link). Wind can, therefore, have a large impact on the route cranes follow during migration and the time of day they pass over locations along the route. But one year is not the same as the next. Differences between years are determined by variations in weather conditions and the ways cranes respond to them. Exactly how that works is still unclear. We don’t know precisely how much wind influences cranes at different stages of the migration. Sometimes they choose to drift with the wind, causing them to deviate from their goal, while at other times they opt to compensate for crosswinds that push them off course. How this unfolds along the entire migration route and what effect it has on the migration over the Netherlands is a question for science to answer. Research led by Dr. Koen de Koning at Wageningen University is, therefore, focused on better understanding these patterns.
New Version of the Crane Migration Radar in Development
Color-coded legend for crane viewing chances
Developments on the crane migration radar continue. Before the autumn migration of 2024, we launched a new version of the Crane Migration Radar, making it easier for users to assess the chances of seeing cranes at a particular location. A legend has been added to interpret the chances with color coding: blue and green indicate very low chances, yellow is slightly higher, and orange and red indicate it's time to pay attention! If you choose to share your location, an icon will appear showing your current position, making it even easier to see your chances.
A major new development is the addition of a 48-hour forecast, allowing you to plan ahead on where to go or when to go outside to spot cranes. This forecast will also be added to the current crane chance map. Currently, this chance is only calculated based on observed groups. But just because no groups have been observed doesn't mean there are no groups flying. Someone has to be the first to spot a group and report it via waarneming.nl! The 48-hour forecast will give a more complete picture of the chances of seeing cranes at different locations. And of course, the chances are greatest when a group has recently been spotted nearby. These chances will still be included in the new version. We hope to launch this version in the autumn of 2025. You can help us bring this update to life by making a donation. Your support keeps it running and helps us make it even better. Every bit helps – thank you!
Student Projects
In line with the development of the new 48-hour forecast and the research into understanding the migration routes of cranes, several student projects have been set up that contribute to the crane migration radar project. In addition to the contributions the students are making to the existing project, it also offers them the opportunity to graduate on the crane radar. A win-win situation!
Crane Migration Radar with Wind Turbine Locations
Two projects focus on better understanding the chosen migration routes. In one project, virtual cranes are simulated in a computer model to explore how different flying strategies of individual cranes play out on a larger scale. In the other project, historical observations are being analyzed to identify general patterns. The biggest challenge in this project is the limitations of the data used. Many observations have been made in urban areas or specific nature reserves, which tell us more about where the observers were, rather than where the cranes were. The results of these two projects will be combined to get a better picture of large-scale patterns in crane migration.
Another project is nearing completion for Xinyu Wang, a student from Wageningen University’s Environmental Sciences master’s program. In her thesis, she is exploring alternative applications of the crane migration radar, specifically to better protect cranes by preventing collisions with wind turbines. While green energy production is of course very sustainable, large wind turbines pose a danger to thousands of migratory birds every year. A collision with the spinning blades almost always results in fatal consequences for the birds. It is crucial to find a balance between sustainable energy production on the one hand and nature protection on the other. How we can optimize this balance, and the role the crane radar can play in this, is the focus of her research.
Help us keep the Crane Radar flying!
We’re truly thrilled by how many of you are using the Crane Migration Radar – your excitement grows every year, and it means the world to us. What you may not know is that the radar is built and maintained entirely by a small but dedicated team of volunteers. Yet, we’re committed to keeping it running, improving its performance, and collecting crucial data to protect cranes. To keep this project alive and growing, we need your help. A tax-deductible donation – big or small – will make a real difference in ensuring the radar continues to operate and evolve.
Thank you for being part of this journey with us. Together, we can keep tracking, learning, and protecting these magnificent birds.