Plastic pollution is a serious global issue. It poses significant threats to wildlife, not only through physical harm from ingestion and entanglement, but also through widespread exposure to plastic additive chemicals (PACs). These PACs, such as plasticizers and flame retardants, can leach into the environment, accumulate in animal tissues and cause harm to health and reproduction.  The herring gull is an ideal focal species in which to explore the damaging effects of PACs, because it has an extremely variable diet, so individuals are likely to vary considerably in PAC exposure. 

In the first study of its kind, we showed that herring gull eggs collected in Cornwall, UK, contain a ‘cocktail’ of phthalates (Allen et al. 2021). Phthalates function as plasticizers, meaning they make plastic products more flexible. However, when phthalates build up in animals’ bodies, it is well known that they can interfere with normal cellular signalling pathways and cause stress. How this impacts reproduction in gulls remains to be studied. 

We also have preliminary data showing that the specific types and amounts of phthalates vary hugely amongst gull nests. This is exactly what we would expect, because some gulls are likely to be specialists in feeding at the coast, whereas others are experts at raiding bins and stealing foods from humans. Our next goal is to understand how individual dietary choices affect the uptake of PACs, and the effects on the development and survival of the chicks that they produce.