Recordaantallen Wespendieven over de Lage Landen in augustus-september 2013

Record numbers of Honey Buzzards over the Low Countries in August-September 2013.
During August and September 2013, two large waves of Honey Buzzards Pernis apivorus flew over the Low Countries. The first wave, on 25 and 26 August was observed in the Netherlands and mid Belgium in numbers which are exceptional for this region (max 746 individuals over Bichterweerd). The cause for the so far westerly shift of the migration corridor, which under normal circumstances runs to the east of the Low Countries, is a typical weather pattern: on one side a low-pressure area with precipitation which comes to a halt above NW Europe and on the other side a high-pressure area above north or central Europe. As the high-pressure area overcomes the low-pressure area, a short and intense migration peak develops of raptors and storks which for days have been driven against the weather front by a strong easterly wind (4-5 Bft.) and have been forced to postpone their migration. The relatively large numbers of Honey Buzzards on 25 and 26 August perhaps indicate moderate success in certain parts of the species’ breeding grounds in NW Europe. The second wave of Honey Buzzard migration, which followed a peak in Falsterbo on 3rd September of 4152 individuals, did not reach the Netherlands and Flanders. A weak easterly wind on 6th September moved the migration corridor over southeast Belgium. In Harze (Luik province), 1079 Honey Buzzards were counted on that day. Although it is becoming clearer that the weather pattern described regularly leadsto record migration over the Low Countries, it remains difficult to predict where precisely the sometimes narrow migration corridor will occur.