Jeroen Onrust


Hi, my name is Jeroen Onrust, 25 years old and in de third year of my PhD in the Animal Ecology group at the University of Groningen. My project is about earthworms and especially about their availability for meadow birds. This group of birds declined dramatically the last decades in the Netherlands because of agricultural intensification. As earthworms are for most meadow bird species the most important prey, it is essential to know the responses of earthworms on agricultural intensification. To study this, I focus on earthworm availability for Golden Plovers Pluvialis apricaria, a meadow bird that does not breed in the Netherlands, but use agricultural grasslands during wintering. Golden Plovers forage almost entirely on earthworms, but can only catch them by sight. Therefore the earthworms have to be active at the surface and they only do so during the night. Golden Plovers have very good night vision and are mostly nocturnal active. To measure earthworm availability for these birds I use a self-made cart to count the surface active earthworms during the night. By using this method at different managed grasslands and with additional experiments in the lab and in the field, I hope to find out which conditions earthworms prefer and which factors determine their availability. So far, it seems that there are species-specific responses on agricultural intensification and especially earthworms that show surface-active behaviour are negatively affected.