Internship: Oystercatcher reproductive performance and earthworm abundance

Research internship (MSc.)


The Eurasian Oystercatcher (Haematopus ostralegus) is a large wading bird whose population has declined substantially in the Netherlands. The causes of the decline are investigated in the project CHIRP. The oystercatcher is widespread during the summer months, occurring along coastal areas and also inland, near the shores of freshwater lakes and rivers or in grasslands, meadows and agricultural areas. The broad variation in feeding habitats also results in a wide variation of feeding phenotypes, such as oystercatchers that specialise on shellfish or worms. Food availability will also vary within a given feeding specialisation. For example, oystercatchers that feed in inland habitats such as arable (ploughed) land, grassland or urban areas where a principal prey item is the earthworm. Research has already been conducted to try to predict the abundance of earthworms (Rutgers et al. 2016), although additional research may be required to include additional environmental variables that improve prediction accuracy. In contrast, little research has been done to relate reproductive success of inland breeding oystercatchers to earthworm biomass.

This project will develop this line of research and the specific aims are to:

  1. Measure earthworm abundance (biomass) during the egg-laying stage (end-April, early-May) and during chick raising stage (mid to late-June) of the oystercatcher breeding season, focusing on inland breeding oystercatchers. Known breeding locations (identified in summer ’2018) will be monitored across different habitats. Earthworm biomass will be linked to the reproductive success of oystercatchers.
  2. The earthworm biomass of sampled areas will be related to the predictive maps of Rutgers et al. (2016) to determine how well earthworm biomass was predicted, and potentially identify alternative environmental variables that improve predictions.


This project integrates

  • Integrates both fieldwork and different analytical approaches, including field sampling of earthworms, recording oystercatcher breeding success and work in the lab to obtain earthworm biomass
  • In addition, a number of modelling techniques may be required to link earthworm biomass to breeding success. Estimating large-scale estimates of earthworm biomass requires species distribution modelling approaches, and hence analytical work conducted through the program R and the use of GIS datasets to prepare environmental variables
  • A strong research project may be publishable and thus we seek a student that would be interested to pursue a peer-reviewed publication following the project


The project will ideally start in March/April of 2019 with a six-month internship. The student will be supervised by Andrew Allen from Radboud University and Magali Frauendorf from the Netherlands Institute of Ecology, but there is intensive cooperation with Bruno Ens from Sovon Vogelonderzoek Nederland.

More information

Please contact, or if you are interested in this project.


Density maps of breeding oystercatchers (left) and earthworms (right) in the Netherlands.

Density maps of breeding oystercatchers (left) and earthworms (right) in the Netherlands.