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.