Posts in Research
New publication: Population trends from 8 years of BRC Autumn Counts

We are proud to announce that counting millions of raptors, over thousands of hours and the help of hundreds of volunteers has now resulted in a new open access publication in Ibis.


Juvenile (left) and adult female (right) Honey Buzzard. Photo by Bart Hoekstra.


For 8 important species for the bottleneck, we have analysed trends over the past 8 years of standardised counts (2011-2018). Despite this short study period, we can already detect moderate changes in abundance for at least one age class in all species except Pallid Harrier. You can find the summary of our results through the button below, or read the paper in its entirety in Ibis.


Wouter M.G. Vansteelant, Jasper Wehrmann, Dries Engelen, Johannes Jansen, Brecht Verhelst, Rafa Benjumea, Simon Cavaillès, Triin Kaasiku, Bart Hoekstra & Folkert de Boer. (2019) Accounting for differential migration strategies between age groups to monitor raptor population dynamics in the eastern Black Sea flyway. Ibis.

BRC goes Open Access

In 2008 Batumi Raptor Count made its first full-season count of migrating raptors along the eastern Black Sea coast. Now, after more than a decade of counts, we are thrilled to announce that the entire BRC dataset, including over 370,000 occurrence records collected between 2008-2017*, has been published open access in GBIF, the Global Biodiversity Information Facility (Figure 1). What’s more, ZooKeys has published our complementary data paper in which we explain exactly how these data were collected, managed and processed (Figure 2), and how to best use our open data for monitoring and research.


Figure 1. The entire* BRC dataset can now be found on GBIF.


Figure 2. Diagram of data management and processing at BRC showing the data registry development from paper based entries in the beginning to the mobile application supported entries since 2015 with subsequent final data processing and upload to the GBIF database.

With more than one million raptors passing through the Eastern Black Sea Flyway every autumn our counts represent a considerable part of the global breeding populations of several raptor species. Moreover, our counts are one of few data sources concerning the state of raptor populations to the north of the Caucasus. Indeed, we think it is not an exaggeration to say that our citizen science project has now delivered a unique benchmark for monitoring the state of raptor populations in the East African-Eurasian migration system during the 21st century!

An important quality of the BRC dataset is that it not only contains information on abundance. Many records also include information regarding the age and sex of birds, allowing us to dig into the demographic changes underlying trends in species abundance. We already analysed recent changes in abundance and demography for eight common raptor species. That work is currently in review so we can’t share the results with you yet, but hope we can do so later this spring!

Looking further ahead, we believe our dataset can be very useful for anyone looking to study migration behaviour of raptors. So don’t hesitate to get in touch if you are a student or researcher with some cool research ideas!

So far open data is far from common practice among bird observatories. However, at Batumi Raptor Count we firmly believe in open data as an integral part of transparent and reproducible science, and we very much hope these publications will inspire our colleagues monitoring bird migration elsewhere to consider a similar approach.

By publishing a data paper we transparently identify key pitfalls in the use of our data. Any third party that wishes to use our data is advised to consult this data paper, and preferably the BRC research coordinator, before using BRC monitoring data for any other specific use. The count strategy of BRC is tailored to local conditions and flight behaviour of raptors in the bottleneck. When using our dataset you cannot just simply add up all numbers to determine daily or annual species totals. One pitfall is that for some species, such as spotted eagles and ringtail harriers, a large number of individuals cannot be identified to species level in the field, and are thus recorded as, for example, ‘Large Eagle Spec.’ or ‘MonPalHen’ (Figure 3 & 4).

Figure 3. Ageing of female Harriers can be challenging and distant birds can be hard to distinguish from juvenile birds under poor visibility. Thus, we record birds as female colored, when they appear to be either in juvenile or female plumage.

Figure 4. Hierarchy of morphological groups used to estimate how many of the ‘unidentified birds’ belong to each species level, shown only for target species at BRC.

We realise these pitfalls complicate the use and arguably restrict the openness of our data. However, we developed scripts in the open source software R to estimate daily and annual species totals from the GBIF dataset, and these scripts are also published open access via Bitbucket. Users that need simplified tables of daily and annual species totals can request these from the BRC research coordinator.

The publication of the BRC dataset in GBIF and the preparation of the accompanying data paper for Zookeys was supported in large part by NLBIF, the Dutch branch of GBIF. We are very grateful to Frank de Miranda and the Dutch Georgian Ornithological Foundation for their help in getting this project going.


* 2018 data will follow as soon as possible. The dataset in GBIF will be updated annually.



Wehrmann, J., de Boer, F., Benjumea, R., Cavaillès, S., Engelen, D., Jansen, J., Verhelst, B. & Vansteelant, W.M.G. (2019). Batumi Raptor Count: autumn raptor migration count data from the Batumi bottleneck, Republic of Georgia. ZooKeys. doi:10.3897/zookeys.836.29252



On social media

We are very passionate about communicating what we do. Did you know you can follow us on both Facebook and Twitter ? BRC co-founder Wouter Vansteelant recently posted a thread on Twitter providing some background information to the data paper and dataset. Start from the tweet below, or click here.


Turns out our dataset is a sizeable addition to the Georgian records in GBIF.

BRC, ResearchAdmin
BRC at IBOC2019

We just returned home from the 3rd International Bird Observatory Conference (IBOC) in Eilat. It was a very successfull get together of people from bird observatories across the globe to share knowledge and experiences. As BRC we are very thankful to the organizers of the IBOC2019 for helping us with part of the funding needed to come to Eilat and for giving us considerable speaking time to present our work in Batumi. Besides topics as project management, count philosophy and data management and our recently submitted paper to IBIS about the relevance of ageing, we are very proud that one of our first Georgian counters, Aslan Bolkvadze, presented the problems of illegal hunting in the bottleneck.

Update May 9th, 2019: Videos and slides of the talks have now been made available. Scroll down to see them. Unfortunately there is no video of the talk by Dries Engelen.


During IBOC2019 the Caucasus region was represented by people from Georgia, Armenia, Germany, Estonia and The Netherlands: a unique moment and an excellent opportunity to discuss cooperation possibilities. Photo by Art Villem Adojaan.

Aslan Bolkvadze presenting the problem of illegal hunting in the bottleneck. Photo by Art Villem Adojaan.


Triin Kaasiku presenting our project, count philosophy and open access availability of our dataset. Photo by Art Villem Adojaan.

Dries Engelen  presenting the team that was at the basis of 8 years of standardised counts. Photo by Art Villem Adojaan.

Dries Engelen presenting the team that was at the basis of 8 years of standardised counts. Photo by Art Villem Adojaan.


Videos & Slides


Batumi Raptor Count: our strategy for the monitoring and conservation of more than one million raptors in the eastern Black Sea flyway

Triin Kaasiku


Illegal killing of birds in the Batumi bottleneck

Aslan Bolkvadze

IBOC2019 - BRC - Dries Engelen.jpg

Accounting for differential migration strategies between age groups to monitor raptor population dynamics in the eastern Black Sea flyway

Dries Engelen


Other talks from the region

Besides presentations about BRC, we would also like to highlight the presentations from our friends from projects in Armenia, Azerbaijan and Turkey.

The branch of German nature protection union in the Republic of Armenia: NABU-Armenia

Lusine Aghajanyan


Research on waders in Southern Azerbaijan, one of the last under-surveyed areas of the Western Palearctic

Christoph Himmel

The development of the Besh Barmag Bird Migration Count in Azerbaijan and its importance for the monitoring of Eurasian migrant birds

Michael Heiss


Establishing raptor migration monitoring at Sarimazi (Turkey) to assess Egyptian Vulture population trends

Steffen Oppel