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GPSlogger onderzoek bij aalscholvers
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Studying the foraging behaviour of cormorants in the Dutch delta with GPS loggers


Example of initial results; foraging trips of two cormorants during the egg stage off the coast south of the Maasvlakte 2.
Distribution of cormorants recorded during aerial surveys in 2009-2011; counts Bureau Waardenburg - PMR monitoring nature compensation in the Voordelta, annual rapport 2011 (Deltares).

In April 2012, we began research into the flight activity and foraging behaviour of cormorants in the Dutch delta.

Around 1,100 pairs of cormorants breed in the Nature 2000 site Voornes Duin at Breede Water in the dunes of South-Holland. Cormorants from this colony mostly forage in the Natura 2000 site of the Voordelta. We aim to study how the birds used these areas, how often and where they forage, where are the important resting areas, what they eat and what is their breeding success.

Combining GPS loggers, pellets and aerial surveys

A total of 11 breeding cormorants have been fitted with GPS loggers. These are attached using a type of harness so that the logger sits on the bird like a small backpack. As for previous projects we have first developed and tested these harnesses on captive birds. Read here the results of these tests in 'Seabird'. Here we have again been thankful for the help of the bird rescue centre de Bonte Piet.

The loggers store information as to the locations of the bird. Later these data are downloaded via a short-wave radio connection in the breeding colony. Furthermore, the diet of the birds can be determined by pellet analysis and breeding success by watching the colony. Aerial surveys provide additional information as to the distributions of cormorants at sea and on sand banks and beaches.

Unique data from GPS loggers: seaward and also landward

We follow the cormorants throughout the entire breeding season; from the end of April until the autumn. The first results are extremely interesting and for some individuals we have location fixes every two minutes. This provides us with a unique insight into the lives of breeding cormorants. Many foraging trips have been documented and it seems that bird not only travel to the sea but also to inland waters. During these foraging trips the cormorants rest to dry out their wings before heading back to the colony. Sand banks, beaches and breakwaters seem to be the most important resting areas.

Monitoring compensation measures in the Dutch Delta

This research forms part of a bigger project being carried out on behalf of Deltares, with finance from Rijkswaterstaat Waterdienst and Havenbedrijf Rotterdam. Within this project compensation measures will be developed in relation to the creation of the Maasvlakte 2 (PMR monitoring natuurcompensatie Voordelta - PMR NCV). The research into cormorants is being carried out in collaboration with specialists from DeltaProjectManagement (DPM) and Rijkswaterstaat Waterdienst.

Permission to work in the colony is granted by Natuurmonumenten and procedures follow nature protection regulations with permits given by the Province of Zuid-Holland, Directie omgevingsdiensten, Afdeling Vergunningen van Bureau Omgevingsvergunning, Groen en Grondwater. Natuurmonumenten have also helped at the Breede Water colony by advising on the best research locations in the colony.

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