Sensing the soil
We are proud to celebrate another milestone in the journey of one of our young researchers. On 23 June 2026, Renée Veenstra successfully defended her PhD thesis at the University of Groningen under the Godwit Landscape Project. Started in 2021, the Godwit Landscape Project uses black-tailed godwits as indicators of the ecological health of Dutch dairy-farming landscapes. Within this framework, Renée investigated the foraging ecology of adult godwits on their breeding grounds.
Although godwits mainly feed on earthworms, researchers knew little about their prey preferences and foraging conditions. Using field observations, DNA metabarcoding, soil sampling, and experiments, Renée revealed a more complex foraging ecology.
Following food beneath the surface
Renée examined godwit diets during two key periods: a. Pre-nesting period (shortly after arrival on the breeding grounds) and b. Post-breeding period (after breeding, before migration). She found a clear seasonal shift in diet, from earthworms in wet spring soils to cranefly larvae (leatherjackets) later in the season and sometimes on spiders, when drier, harder soils make earthworms increasingly difficult to access.
One of the thesis’s key findings was that godwits are selective feeders, preferring red earthworms even when grey earthworms are more abundant. This challenged the assumption that all earthworms are equally valuable and showed that prey quality, accessibility, and abundance shape foraging behaviour. Red earthworms may be easier to detect, more accessible, or nutritionally superior.
The importance of moist grasslands
A central theme throughout the thesis was the importance of soil moisture. Experimental work using geophones showed that moving earthworms generates stronger and more detectable vibrations in moist soils, particularly red earthworms. These findings support the idea that godwits use specialized sensory receptors to locate prey beneath the soil surface. Moist soils improve both prey accessibility and detectability.
Field studies showed that traditionally managed grasslands support more red earthworms than intensively managed fields. Higher water tables and favourable soil conditions provide more reliable food resources throughout the breeding season, highlighting the importance of maintaining moist grasslands to sustain godwit populations in an increasingly drought-prone landscape.
Growing as a researcher
Renée’s interest in meadow birds grew from earlier work on soil fauna, decomposition processes, and lapwing conservation. Her PhD combined these interests to explore how below-ground ecological processes influence godwits. Along the way, she developed skills in research design and fieldwork coordination, while learning to cope with uncertainty. She credits the supportive BirdEyes and Godwit team for helping her grow as a researcher, especially through discussions and constructive feedback. ‘Being altogether on every Wednesday, the afternoon discussion on ongoing research was very nice for me because it helped to shape the next steps, and I think it should continue,’ said Renée.
Renée’s research revealed how prey behaviour, soil conditions, and grassland management shape food availability for godwits. Her findings can inform future conservation efforts, and she hopes to continue exploring other ecological aspects of meadow bird conservation.
