How do our skylarks winter?

Cheerful birdsong on high – summer would be unthinkable without the skylark. Yet the Netherlands has seen a drop in nesting pairs of nearly 95% since the early 1970s. Until recently, very little was known about how they wintered,  although that is where opportunities lie to protect them. This is the result of recently published research conducted by Arne Hegemann and his colleagues at the University of Groningen in conjunction with the Vogeltrekstation, the Dutch centre for bird migration and demographics.

Birds who make their homes on farmland are very much on the decline and in recent decades their numbers have dropped by 50% in Western Europe. In the Netherlands the skylark (Alauda arvensis) tops the decline charts. Its numbers have dropped by nearly 95% since the early 1970s, falling from a onetime 700,000 nesting pairs to 38,000 pairs at present.

Year-round protection

Until now, the decline in farmland birds had mostly been blamed on changed circumstances during the breeding season: nest destruction due to farming activities, less food for the young, and so on. What the contribution of their winter circumstances was to the decline in numbers was unclear. Not only that – there was little knowledge at all about what Dutch skylarks did during the winter. Yet such knowledge is paramount for providing the birds year-round protection.

Two strategies

Do Dutch skylarks spend their winter at the breeding grounds or do they head south? Both are the case, University of Groningen’s Arne Hegemann recently concluded in an article in the ornithological journal Ardea. Apparently, Dutch skylarks have two different wintering strategies – while a number of them head for foreign parts in southwest Europe, others remain near their breeding grounds. The resident skylarks also receive company from skylarks arriving from northern and eastern Europe.

Protection

Maintaining and protecting the Dutch breeding population is only possible if the skylarks survive the winter well.  However, farming methods have changed, resulting in a drop in winter fodder for those birds that prefer fields for foraging. The research emphasizes that protective measures must also apply to winter circumstances, both in their wintering areas in the Netherlands and in southwest Europe.

Transmitters

Hegemann and his University of Groningen colleagues, in conjunction with the Vogeltrekstation, analysed the ring data of over 88,000 skylarks collected by the latter since 1911. The Groningen biologists also studied the migratory behaviour of 27 skylarks from the Aekingerzand (Drents-Friese Wold National Park) area during the winters of 2007-2008 and 2008-2009. They outfitted the skylarks with transmitters in late summer and kept track of them all winter using a receiver.

Migrate or stay – why?

The discovery that a breeding population comprises resident birds and migratory ones may perhaps help answer an age-old scientific question: Why do some birds head south in winter and why do others not follow suit? In other words, which strategy leads to the most offspring under which circumstances? The mixed population of skylarks will provide an opportunity to investigate the pros and cons of migration versus sitting tight.

Implementation and funding

The research project was led by PhD student Arne Hegemann, who is a member of Professor Irene Tieleman’s Animal Ecology group at the Center for Ecological and Evolutionary Studies of the University of Groningen. The research was co-funded by the Dutch environmental organization Vogelbescherming Nederland (Netherlands Bird Protection) and funded by grants from the Schure-Beijerinck-Popping  Fund, the Dr J.L. Dobberke Association and the Deutsche Ornithologen-Gesellschaft.

Meer informatie

- Source: Hegemann A., H.P. van der Jeugd, M. de Graaf, L.L. Oostebrink and B.I Tieleman (2010) Are Dutch Skylarks partial migrants? Ring recovery data and radio-telemetry suggest local coexistence of contrasting migration strategies. Ardea 98: 135-143, www.ardeajournal.nl
– Contact: Arne Hegemann (Dutch-speaking), Animal Ecology, Center for Ecological and Evolutionary Studies, University of Groningen, e-mail A.Hegemann rug.nl, tel. 050-363 3409