Black-necked Grebes (Podiceps nigricollis) know how to use favorable conditions surprisingly spontaneously in individual years, as if “scouts” were permanently on the move, which guide other birds to new habitats and locations. One example is the spontaneous emergence of a breeding colony at the Alfsee in the Landkreis (district) Osnabrück in Lower Saxony in June 2011 with 52 pairs which tried to use the favorable conditions through the mass occurrence of emergent water plants. It goes without saying that not all breeding occurrences emerge and disappear so quickly; there are also numerous breeding sites that have been occupied for decades and are often located near colonies of gulls, especially those of the Common Black-headed Gull (Larus ridibundus).
One other example is an occurrence in southern Brandenburg. In a vast shallow lake area, the Rietzer See near Kloster Lehnin, the numbers are impressive since the beginning of counting and on April 13, 2012 more than 110 Black-necked Grebes were counted.
It was not until 2011 that the first Black-necked Grebes appeared at the Reckahner ponds, also in the municipality of Kloster Lehnin, but in a fish pond farm. Then there were no more reports for 7 years and then from 2018 onwards some reports, which then culminated in a number of half a dozen breeding birds in 2020. Thus, you can see a high level of local variability on Brandenburg localities as well.
Basically it can be said that Black-necked Grebes can be found in Central Europe all year round. Meanwhile, the magnitudes in winter are at the level of the numbers for the breeding season. They can be observed as breeding and resting birds in all regions, but many of the 900 to 1100 pairs (over the period from 2011 to 2016) are concentrated in a few larger colonies. After increases in many regions up to the 2000s, the last analysis of the population situation assessed both the 12 and 24 year trend as a moderate decrease. However, the breeding occurrences are characterized by high spatial and temporal dynamics.
The currently known moulting sites seem to have a higher degree of constancy in the local occupation. The most important body of water in this regard in recent years was the Helmestausee Berga-Kelbra south of the Harz Mountains on the Saxony-Anhalt / Thuringia border. There is also a larger breeding colony here. In almost all the years examined between 2012 and 2020, several hundred Black-necked Grebes were found there in midsummer. In two years it was probably even more than 1000 individuals, including the immature birds. Other important moulting lakes in Germany with sometimes several hundred individuals are located on Dassower See on the lower reaches of the Trave, in the Wismar Bay, in the renatured polders of the Peene Valley, on Lake Constance and especially on the Ismaninger reservoir northeast of Munich. So far there are only few indications of the origin of the moulting population of the Black-necked Grebe. It can be assumed that a large part of the birds come from the German breeding population. However, due to a major “bird flu” outbreak at the Helmestausee in 2007, it became known that five birds ringed in Spain were among the birds that died. On the basis of the ringing data, it cannot be clarified whether it was a question of young birds that migrated to southern Spain to winter there or of Spanish breeding birds that moulted in central Germany.
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Thanks for the interesting article.
Can you please contact me? I have questions about Black-necked grebe ecology.