Journal of Ornithology

, Volume 158, Issue 3, pp 753–760 | Cite as

Rare case of an adult male Montagu’s Harrier Circus pygargus over-summering in West Africa, as revealed by GPS tracking

  • Iben H. SørensenEmail author
  • Almut E. Schlaich
  • Raymond H. G. Klaassen
  • Henning Heldbjerg
  • Ben J. Koks
Original Article


Over-summering within or near the African wintering range by immature, non-breeding individuals occurs regularly in several species of long-distance migratory raptors, yet the extent of over-summering in Africa by adult birds remains unclear. In this study, we describe a case of an adult Montagu’s Harrier over-summering in Africa, as revealed by GPS tracking. By relating detailed knowledge of the bird’s movements to remotely sensed environmental data (normalized difference vegetation index, NDVI), we show that over-summering in this case was likely related to an exceptionally difficult breeding season the previous year rather than an effect of adverse weather conditions encountered during the winter or a failed attempt to migrate. Various factors are discussed as potential driving forces behind the bird’s intra-African movements. Finally, we relate the documented case to a large number of North European Montagu’s Harriers studied by telemetry and show that over-summering in Africa by adult individuals is indeed a rare event.


GPS tracking Remote sensing Raptor migration patterns Circus pygargus Behavioural ecology Over-summering 


Seltener Fall von Übersommerung eines adulten Wiesenweihenmännchens Circus pygargus in Westafrika enthüllt durch GPS-Tracking

Übersommerung innerhalb oder nahe ihrer afrikanischen Überwinterungsgebiete kommt bei immaturen, nicht-brütenden Individuen verschiedener langstreckenziehender Greifvogelarten regelmäßig vor. Das Ausmaß von Übersommerung bei adulten Vögeln in Afrika ist jedoch noch undeutlich. In dieser Studie beschreiben wir einen Fall von Übersommerung eines adulten Wiesenweihenmännchens in Afrika, der sich dank GPS-Verfolgung offenbarte. Durch die detaillierten Kenntnisse der Bewegungsmuster des Vogels in Beziehung zu setzen zu ökologischen Daten aus der satellitengestützten Fernerkundung (Normalized Difference Vegetation Index, NDVI), zeigen wir, dass die Übersommerung in diesem Fall wahrscheinlich eher im Zusammenhang mit einer außergewöhnlich schwierigen Brutsaison im vorausgegangenen Jahr stand, als eine Folge von widrigen Wetterbedingungen im Winter oder einem fehlgeschlagen Zugversuch war. Diverse Faktoren werden als potentielle treibende Kräfte hinter den inner-afrikanischen Bewegungen des Vogels diskutiert. Schließlich setzen wir den hier dokumentierten Fall in Bezug zu einer großen Anzahl von nordeuropäischen Wiesenweihen, die anhand von Telemetrie verfolgt worden sind und zeigen, dass Übersommerung eines adulten Individuums in Afrika in der Tat ein seltenes Ereignis ist.



We dedicate this article to the memory of Michael B. Clausen (1961–2017) and to his son Jeppe. We thank Villum Fonden, the Danish Nature Agency (ref. NST-304-00068) and DOF-BirdLife Denmark’s Projekt Hedehøg for financial support to carry out the GPS tracking study in Denmark. In addition, thanks to all Danish farmers collaborating with us to protect the local breeding pairs of Montagu’s Harrier, and to Willem Bouten and the UvA-BiTS team for technical advice. Michael B. Clausen, Lars M. Rasmussen and Mathilde Lerche-Jørgensen carried out essential fieldwork. We are grateful to Steffen Oppel and one anonymous reviewer for constructive comments, and to the Ringing Section at the Natural History Museum of Denmark for providing licenses for trapping and tagging adult Montagu’s Harriers.

Compliance with ethical standards

The authors declare that they have no conflict of interest.

Capturing, handling and tracking of harriers was carried out under license from the national authority (the Ringing Section at the Natural History Museum of Denmark).


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2017

Authors and Affiliations

  • Iben H. Sørensen
    • 1
    • 2
    Email author
  • Almut E. Schlaich
    • 3
    • 4
  • Raymond H. G. Klaassen
    • 3
    • 4
  • Henning Heldbjerg
    • 1
    • 5
  • Ben J. Koks
    • 3
  1. 1.DOF-BirdLife DenmarkCopenhagen VDenmark
  2. 2.Danish Hunters’ AssociationRøndeDenmark
  3. 3.Dutch Montagu’s Harrier FoundationScheemdaThe Netherlands
  4. 4.Conservation Ecology Group, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
  5. 5.Department of Bioscience-Wildlife EcologyAarhus UniversityRøndeDenmark

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