Tracking down the wintering area of great reed warblers

Staffan and Arzu attaching a geolocator to a great reed warbler

Thousands of water buffaloes roam the Kızılırmak Deltası
There are now 14 male great reed warblers with geolocators in the Kızılırmak Deltası, situated along the Black Sea coast in northern Turkey. The loggers were attached last week, 12-18 June 2013, in collaboration with Dr. Arzu Gürsoy and colleagues at the Ondokuz Mayıs Üniversitesi, Samsun, Turkey. The purpose of the study, coordinated by the CAnMove researchers Staffan Bensch, Bengt Hansson, Dennis Hasselquist and Maja Tarka, is to obtain data on migration routes and African wintering quarters for various populations of great reed warblers in Europe and Western Asia, to compare with the detailed knowledge we have obtained from our long term study of the species in lake Kvismaren, Sweden. The particular site at the Kızılırmak Deltası we had selected last year, a 10 meter wide canal bordered with narrow reads, had unfortunately been dredge during last winter which completely had destroyed the habitat and consequently there were no great reed warblers there. After searching several nice looking places without any success, we decided to go to one of the lakes in the delta, Cernek gölü, where a Dutch team had carried out a detailed survey of all marshland birds about 20 years ago and reported 300 territories of great reed warblers. In the NW corner of the lake, supposed to contain >50 pairs we could just find one male singing. We started wondering if we were too late in the season. Because many other bird species were actively singing (e.g. savi's warblers, reed warblers, bitterns, cuckoos, etc) it would have been remarkable if great reed warblers with its extended breeding period already had stopped singing for the season which gave us trust to continue searching. It was not until the third day we found a population of birds along the main Kızılırmak River. The great reed warblers were spread out over several km but easy to find in small pockets of reads and in most places easy to catch. Several of the males had nest building females and the nests we found contained eggs – hence it seems that the breeding cycle was not substantially more advanced than in Sweden.

Great reed warbler breeding habitat along the Kızılırmak River

Clearly something has happened to the great reed warblers in the delta since the Dutch census. The Kızılırmak Deltası (560 km2) is just amazing for all other kinds of wetland birds, holding e.g. 1000 pairs of white storks, 1000 purple herons, 3000 purple gallinules,
300 marsh harriers, etc. It is therefore enigmatic why the great reed warblers seem to have almost disappeared from this thriving wetland. Knowledge of the migration routes and wintering area of this population might help to answer this question. İnşallah, we keep fingers crossed that some of the birds will return to the Kızılırmak River next spring, with nice data on their wintering travelling stored in the loggers.

Staffan Bensch  


Photographs: Arzu Görsoy

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