Meerkoet bevrijdt Unionidae van driehoeksmosselen

The decline in unionid populations can be partly due to high densities of Zebra mussels growing on their shells by which the unionid can not open their valves and dies. Coots (Fulica atra) feed among other food on Zebra mussels (Dreissena polymorpha). They dive to catch them. When they return to the water surface with a Zebra mussel in their bill, they break the byssus threads by back and forth movements by their head and the unionid is hurled away. In this way the unionid can fall down into the water, upon floating leaf blades of waterlilies or in the helophyte vegetation. They reduce in this way overgrowth by Zebra mussels on unionids.