Black-winged Kite in the Chorokhi Delta
 

A few days ago the spring count team made another visit to the Chorokhi Delta, as the weather was unlikely to offer good migration conditions for raptors. The area right on the southern edge of Batumi is an important breeding area, stopover site for migratory birds and a hotspot for rare vagrant birds. This time the area did not disappoint once again: the BRC team found a Black-winged Kite, the 2nd individual for Georgia!

 
 

Sunday 21st, 2019: As the weather was not looking very promising on the station, we headed out for the Chorokhi delta. Right after entering the delta we found 2 Greater Spotted Eagles flying, with a possible third one next to them. The surroundings around the road provided us with Tawny Pipits and some Short-toed Larks. Further in de delta we found a stunning Whiskered Tern and Citrine Wagtails. Another hunting Greater Spotted was a welcome sight after seeing them only casually flying around. 

After we came back from the river mouth, Ron realised he lost his phone somewhere. We retraced our steps towards the place Ron had slipped, thinking that it might have dropped out of his pocket at that place. Unfortunately, we were not able the retrieve the phone, but... as we were walking back to the beach, Erik — who first thought he was looking at a strange hovering Hen Harrier — suddenly exclaimed 'Grijze wouw! Grijze wouw!'. It took a second before he realised he didn't follow the protocol and shouted equally excited as before, 'Black-winged Kite!', giving the non-Dutch-speakers the much needed translation. 

The bird was extremely polite and allowed us to have good views on it and to identify it as a 2nd calendar year bird of the subspecies vociferus, with the darker secondaries almost forming a trailing edge (like in Hen Harrier, hence the confusion). The closest known breeding location for this subspecies is in Israel, which is quite a distance away for a non-migratory bird. We enjoyed the bird for a couple of minutes while it was hovering just a few meters away, then it flew of out of sight. 

 
 

There are very few records of this species in Georgia, and the species has not been seen from our count stations during the raptor counts (but is high on the wish list). According to this article about Black-winged Kite occurence in the WP (Ławicki & Perlman, 2017) the breeding population (of the subspecies vociferus) is increasing, and it is becoming more likely. As for Georgia, according to this article, it is only the 4th individual of this species in Georgia. But we doubt this information, as there was only one individual in the georgia.observation.org database observed by several observers. We checked this information, and Alex Rukhaia confirmed he is not aware of other records then this single one in september-october 2013 that lingered around Ninotsminda for several days.

It goes without saying that we concluded it was a very good day in the delta and at dinner we enjoyed it even more with some famous Georgian wine.

 
Spring Count Update
 

After 3.5 weeks of counting it is time for a little update on how things are going in the first ever official spring count in Batumi.

 

Black Kites in front of the Batumi skyline. Photo by Diego Jansen.

 

Where to start? Well, let's start with the beginning of the day: unlike in autumn, where you are woken up by just the sound of the local rooster calling, in spring he's joined by a choir of feathered friends. Next to our lovely guesthouse a male Common Redstart (samamisicus, the Caucasian subspecies) has his territory, which he shares with a Semicollared Flycatcher, both nice birds to see before you’ve even had your breakfast. After a good Georgian breakfast we head up to our spring station, which is situated just behind Station 1, our main counting station during the autumn. From there we have a good view of the incoming birds from the south.

Photo compilation of a Black Kite catching small insects while mid-air and on migration. Photo by Diego Jansen.

During the first few weeks the day usually started with a decent stream of Black Kites flying over the sea! Quite a surprising route, as you would expect them to avoid flying over this type of surface due to the lack of thermals. From the data of GPS-tagged kites and from our own observations we have seen that they often fly over the Batumi bay; instead of following the coastline they simply take the shortest route north, which happens to go over the sea for quite a while. Flying over the sea comes with a benefit though, as kites are known to be great at catching fish. We have actually observed them catching fish while migrating. Eat your heart out Osprey! But the hunting doesn't stop at the water's edge. On multiple days we have observed Black Kites catching small insects while they were flying over the station, actively changing direction and swooping in order to catch the bugs. Amazing behaviour, not observed during the autumn count, probably due to lack of available prey, or perhaps because the southbound route provides them with other available food sources? Who knows. Apart from this very interesting migration strategy the numbers are also mind-blowing. With a peak day of 41.000+ black kites, we have beaten our autumn record not only for the peak day but also for the season total number: as of the 14th of April we have counted over 190.000 Black Kites, and more are yet to come. The 200K mark is within hands’ reach!

 

Sometimes you don’t need to go to the botanical garden to see one: photo compilation of a Krüper’s Nuthatch visiting the Sakhalvasho station. Photo by Diego Jansen.

It goes without saying that the Black Kites are not the only raptors migrating. They are accompanied by the usual suspects: Steppe Buzzards, Marsh Harriers, and Lesser Spotted Eagles. However, two relatively rare partners have joined the journey as well: from the station we saw a Golden Eagle and a Cinereous Vulture moving north together with the kites and buzzards. On another afternoon, two young Imperial Eagles decided to put on a show, with one trying to steal prey from the other, occasionally interlocking their talons and spiralling down towards the ground. Never a dull moment in Batumi. And when the raptors are not present, we are kept company by a Sardinian Warbler, only the third record in Georgia. Perhaps the species is much overlooked in autumn but easy to find in spring? Other passerines have also come to greet us on the station: we had a visit from a Red-breasted Flycatcher, Ortolan Buntings, and a Krüper’s Nuthatch, the latter being a much sought-after species here in Batumi. The air around us is also filled with passerines and other small migrating birds. Imagine the summer sound of screaming swifts while counting a stream of Black Kites. Spring is the time of the year!

 

Short-toed Eagle passing by closely. Photo by Diego Jansen.

Light-morph Booted Eagle. Photo by Diego Jansen.

In autumn adult Black Storks don’t look this neat anymore. Photo by Diego Jansen.

 

As for the other monitored species, the numbers are trailing a little behind the numbers we count during the autumn count still. Some might take a different route when flying towards their breeding grounds, while others have yet to arrive. The most anticipated of them is of course the main star of the the Batumi show: the Honey Buzzard. In autumn we count roughly 500.000 of them, but in spring we expect they may show up in even bigger numbers. Some counters have even placed a bet for 800.000! Not sure what to expect, but it will be a spectacular event without a doubt.

 

To be able to count this many birds we need a solid team present, and the good news is that we are still looking for people to add to the current group. So, if you want to take part in migration count history, do not hesitate, and join us in writing this new chapter of the Batumi Raptor Count.

 
 

Written by Diego Jansen & Katharine Khamhaengwong

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.

 

Citation

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