CHIRP: research on the Oystercatcher

The Centre for Avian Population Studies (CAPS) is investigating the cumulative effects of human activities on threatened shore and meadow bird populations.

For more than a quarter of a century, the number of Oystercatchers has been rapidly declining. For a species with a more than 40-year lifespan, an annual decline of 5 % is a drastic population decrease. The important objectives of the CHIRP project - Cumulative Human Impact on biRd Populations – are as follows; to determine the cause of the decline, and to formulate a management action plan to reverse the trend. This is only achievable if all negative influences are thoroughly examined, including the cumulative effects.

These negative influences are not confined to the Oystercatcher overwintering areas, like the Oosterschelde, where the mud flats are disappearing due to the belated effects of the floor barriers. In the Wadden Sea, the Japanese oysters are becoming increasingly abundant in the mussel beds. Additionally, there are substantial complications in the different breeding areas. The agricultural breeding areas are progressively becoming intensively managed and in saltmarshes birds are experiencing increasingly frequent nest lost as storms are washing them away.

The population model

The population model will utilize existing knowledge and new monitoring data, so that the model will be applicable throughout the Netherlands. Furthermore, carry-over effects will be taken into account. Specifically, the model will include the influences of the overwintering conditions on the birds breeding success. Dose-effect relationships, which are supported by scientific studies, are also important to this model.

GPS transmitters

In order to measure the impact of disturbance, a large number of Oystercatchers will be fitted with advanced GPS transmitters. With this technology, detailed information can be obtained to determine the effect of disturbance on both short-term and long-term behavioural patterns. Furthermore, Oystercatchers have been colored ringed in more than 30 regions in the Netherlands. An extensive citizen science network, which was set-up in 2008 during the ‘Year of the Oystercatcher’, contributes to the research by reading these color rings throughout the year and entering these sightings to These observations offer insight into the breeding success, survival, as well as the whereabouts of young and old individuals. Afterwards, the information can be linked to the habitat and weather conditions.

Relevant stakeholders

The Technology Foundation of the Netherlands Organization financed this project, because they want to facilitate the knowledge transfer between research development and those who utilize the technology. The application is just as important as the quality of the research. Therefore, the research project is being collectively supervised by representatives from the following stakeholders; Deltares, The Royal Netherlands Air Force, NAM (Dutch Petroleum Company), Dutch Natuurmonumenten (Society for Nature Conservation), Province of Friesland, Rijkswaterstaat, Staatsbosbeheer and BirdLife Netherlands. The subsequent stakeholders are funding the project. The Dutch Petroleum Company wishes to examine the effects of the subsidence on the Oystercatchers, which breed on the Ameland saltmarsh. The Air Force is interested in the effects of training exercises, which fly over the Vliehors, on the Oystercatchers resting on the island during high tide. Deltares wants to examine the effects, at the population level, of the water management projects, while BirdLife Netherlands wants to formulate a successful conservation plan for this threatened species.

Research institutes

The Centre for Avian Population Studies (CAPS) is implementing this research. The following research institutes are members of CAPS: Radboud University, Netherlands institute for Ecology, and Sovon (Dutch Centre for Field Ornithology). For more information, contact: Hans de Kroon (RU), Eelke Jongejans (RU), Martijn van de Pol (NIOO-KNAW), and Bruno Ens (Sovon).


Project CHIRP (Cumulative Human Impact on biRd Populations) is a collaboration between the Netherlands Institute of Ecology, Radboud University and the Sovon Dutch Centre for Field Ornithology as a part of the newly established Centre for Avian Population Studies. The Technology Foundation of the Netherlands Organization funds CHIRP for Scientific Research (NWO-STW).

CHIRP aims to develop a modelling framework that integrates how various human activates (e.g. climate change, agriculture, mining, fisheries) act at different spatial and temporal scales affect metapopulation numbers. The model will use this knowledge to identify mitigation actions to minimize the impact of human activities and develop the best conservation strategy to help species recovery.

CHIRP will use the well-studied Eurasian Oystercatcher in the Netherlands as a case study. The project will combine new field data collection (e.g. using GPS trackers to assess the impact of disturbance on birds) with the development of new hierarchical models that link eco-physiological, demographic, and migratory processes (based on the vast literature of this species as well as new large citizen science datasets).