Between Polesia and Zambia: a Polesian eagle chooses a very unusual wintering site in Africa

Greater ​S​potted ​E​agles from Polesia are about to start their autumn migration southwards. Their wintering sites are scattered across Europe, Asia and Africa: these birds spend the cold season in​ the​ Balkan Peninsula, Israel, South Sudan, Zambia, and even South Africa. Thanks to GPS-tracking, we not only have a chance to discover migration patterns that are important for​ the conservation of this rare species, ​but also ​learn​ many​ ​​curious details ​that make even experienced scientists surprised. One of these was recently discovered and described by ornithologist Valery Dombrovski.

Liada is a female eagle nesting in the Mid-Pripyat Nature Reserve in Polesia. She spends every winter in Zambia, in a tiny area of only 3 square kilometers. This is too small even for a Greater Spotted Eagle, but Liada is a hybrid between ​G​reater and Lesser Spotted ​E​agles. Typically, wintering​ ​​L​esser ​S​potted ​E​agles have several feeding sites located at a significant distance from each other. ​Because of this, ​vast wintering areas of tens of thousands of square kilometers are formed.

Polesian Greater Spotted Eagle Liada in Zambia. Photo credit: Brett Lewis

Wintering grounds of ​G​reater Spotted ​E​agles are much smaller;​​ however, they usually also reach dozens of square kilometers. It means that Liada is an exception to the general rule. Every day, she flies only a couple of kilometers from one part of the forest to another. How can she survive in such non-typical conditions? I had to dig ​deep​​ ​​into ​the internet to figure it out. Fortunately, this part of Zambia is well known to scientists and naturalists. The area belongs to the Kasanka National Park​,​ famous for its biodiversity. It is home to various species of bushbucks, blue monkeys, and about 400 bird species. And then I found out that one of the most famous natural “shows” occurs in Kasanka annually, and it attracts numerous tourists from around the world.

From​ the​ middle​ of​ October to late December, over 10 million​ ​of Eidolon​ ​​F​ruit ​B​ats (Eidolon helvum) congregate in Kasanka. All of them arrive​ in ​the wetland forest with ​a ​total area of about 2 ha​,​ thus forming the highest density of mammals in the world. Eidolon ​F​ruit ​B​ats are​ quite b​​ig​​​ ​​– their weight can reach 350 g. The enormous number of resting bats causes tree branches to bend and even break.

Millions of bats fill the sky, Kasanka NP. Photo credit: Will Burrard-Lucas

No wonder that the congregation of bats attracts numerous predators. The forest turns into a feeding ground for birds of prey. In addition, there are crocodiles, snakes and l​​eguans waiting for some unfortunate bat to come​ tumbling down​​.​

And what about our Liada? Is she part of this natural spectacle? Yes, she is! She arrives in Zambia in late October, simultaneously with the bats, and then visits the bat forest almost every day. Obviously, Liada like many local predators, feeds on this mysterious natural phenomenon – ​the ​mass congregation of Eidolon ​F​ruit ​B​ats in the same place.

The yellow line on the map indicates Liada's wintering ground of 3 square kilometers in total. The red line marks the boundaries of the "bat forest" where millions of fruit bats congregate. The blue marks show Liada's location during the wintering period - from October to February.

Isn’t this impressive? Liada nests in Polesia, looks and behaves just like dozens of other​ ​​G​reater ​S​potted​ ​​E​agles, but at the same time she is the link that connects us to an outstanding natural phenomenon in a different part of the globe. What secrets ​do ​other ‘ordinary’ ​G​reater ​S​potted ​E​agles​ ​​hold​? We can only guess and hope for new, unexpected discoveries.

The top image features Greater Spotted Eagle Liada in flight. The photo is taken by Brett Lewis in Kasanka National Park, Zambia.

The project “Polesia – Wilderness Without Borders” is part of the Endangered Landscapes & Seascapes Programme and is funded by Arcadia. The project is coordinated by Frankfurt Zoological Society (FZS).

This post is also available in BLR.