From counts to knowledge: research in progress at BRC
While Batumi Raptor Count has hosted student internships and dissertations for many years, our popularity among students of bird migration rose substantially in recent years, to the point that our Research Coordinator has been struggling to accommodate all requests. Strap in for a overview of what research is being conducted at BRC right now.
Comparing relative timing of different species of raptors between the Pyrenees (red) and the Caucasus (blue)
First and foremost, after the successful completion of our last spring count earlier this year our new chairman Tohar Tal will soon be submitting a paper on the first full-season description of Batumi spring raptor migration to a peer-reviewed ornithological journal. Now a student at University of Groningen (NL), Tohar will describe spring abundance and timing of raptors in Batumi for the first time, and also contrast seasonal flight paths through the bottleneck.
The spring data are also being included in a study of sex differences in seasonal migration timing of Pernis and Circus species at Batumi, led by Marc Heetkamp. Marc completed a literature study on this topic as part of his education at the University of Utrecht (NL) last spring, and is now proceeding with analyses.
Beyond using just count data, Elien Hoekstra is using digital photography to study the moult of migrant raptors. Elien got a great grade for her dissertation at Van Hall University of Applied Sciences this year (NL). Now a MSc student at Wageningen University (NL), Elien aspires to publish her interesting results in a reputable ornithology journal.
In addition to the more advanced projects above, several students have initiated new projects after participating in this year’s autumn count. Two of them are actually combining BRC data with high-quality count data of other sites to look at larger scale patterns in migration.
For example, some species like Black Kite are known to migrate much earlier in the western than the eastern flyway (Fig1, top panel). Michaëla Berdougo, based at Lund University (SW), obtained data from count sites in the French and Spanish Basque country — situated at the same latitude as Batumi — to investigate how common it is for different (sub) species to show differences between western and eastern flyways, and why this may be.
Isaac West, geography student at the University of Cambridge (UK), is using historic count data from SPNI in Israel from 1990-2013 and BRC data from 2011-2022 to study whether raptor migration timing has shifted in our flyway in response to climate warming. Against our expectations, his results indicate that autumn raptor timing has changed very little over the past 3 decades!
Zooming in on the Batumi bottleneck again, Joachim Pintens completed a full-season internship as assistant coordinator, and is now proceeding with a study of Booted Eagle migration for a BSc. Dissertation at Ghent University of Applied Sciences and Arts (BE). He is comparing the seasonal abundance and timing of dark morph and light morph individuals, which may offer clues about the geographic origin of these birds.
Number of flocks of different sizes recorded at BRC during standardized daily time periods (sunrise + 1h to sunset – 2h) during 11 autumn counts since 2011.
Finally, our long-time president Dries Engelen is preparing a descriptive study of European Roller migration at Batumi. The abundance, and especially the occurrence of loose but large flocks in Batumi (as many as 240 birds together, Fig2) seems to be rather unique in the world. After consulting many specialists and old literature from across the species range we’ll be writing up our findings soon.
Spring Report 2022 published
An adult male Pallid Harrier treating us to some nice views. Photo by Tohar Tal.
The third and final spring count gave us beautiful snow-covered surroundings and raptors in perfect light, we witnessed the return of birds and spring. We had great views of close-by flying raptors and many medium-raptors far away, Black Kites foraging in the evening light and many more interesting observations.
Have fun reading!
Already 400K raptors during the 3rd and final Spring Count
The 3rd pilot Spring Count is already halfway through, we have been counting for one and a half months and have already counted 400k raptors this season.
A classic spring view: Black Kites in front of the Batumi skyline. Photo by Marc Heetkamp.
For the first three weeks weather conditions were bad with heavy snowfall, which made counting difficult. But in the short periods without rain and snow, we were still able to count some raptors and enjoy the passerines around the station. From the 21st of March on, the weather finally started to clear up and migration was on! And with the still cold and snowy surroundings -we were standing in 30cm of snow- the increasing number of raptors made up for it. We were counting thousands of Black Kites and Steppe Buzzards and lots of large eagles. And even saw insane numbers of Imperial Eagle (26), Greater Spotted Eagle (53) and Short-toed Eagle (204) in a day! What makes these kinds of numbers (and in general raptor migration) even more enjoyable is the close fly-bys paired with great light conditions from the snow, which makes for wonderful views and photos. Towards the end of March, we were counting 20k+ raptors a day (most of them Black Kites), often in messy streams in every distance code. That is the Spring Count for you, thousands of birds to count by only a few counters. But that was nothing compared to the 1st of April, when we counted 56k+ raptors! Black Kites and Steppe Buzzards everywhere, massive kettles and streams everywhere. To count this big mess is a challenge, but our counters thrived on the chaos and adrenaline and managed just fine (of course we counted a lot of medium raptors).
An unusual white bird in an unusually white landscape. A Short-toed Eagle making its way through the snowy bottleneck. Photo by Marc Heetkamp.
It's now almost halfway April and we are still counting over 10k raptors a day and even found 4 Rough-legged Buzzards this season (2 in one day on April 9)! The snow is gone, flowers are starting to bloom, butterflies are flying around, and passerines have started to sing: spring is here!
Red-breasted Flycatcher. Photo by Marc Heetkamp.
Bugle. Photo by Elien Hoekstra.
Semi-collared Flycatcher. Photo by Marc Heetkamp.
We still have over 1 month to go, and we are eagerly waiting to see what more is to come. After this third and final pilot Spring Count we will process all our spring migration data and we plan to publish these results in the near future.