Investigating Lesser Black-Backed Gulls (<i>Larus fuscus</i>) Scavenging Fishery Bycatch as Sentinels of Heavy Metal Pollution in Kerala

Globally, gull species are considered one of the apex predators of the marine environment, which has a generalist foraging behaviour. The scavenging behaviour of gulls is gaining much importance in foraging studies due to their rapid adaptation and generalist foraging patterns. This study explicitly examines the foraging habits of Lesser Black-backed Gulls (Larus fuscus) in the area of fishery bycatch drying in Kerala. It was observed that these gulls predominantly feed from these areas and nearby water bodies rather than engaging in their innate foraging behaviours. This adaptive scavenging behaviour alters their usual broad foraging habits, leading them to spend considerable time near the bycatch drying areas. We also examined the possibilities for considering the migratory species as bioindicators of heavy metals (HM) in the environment, with feather analysis proving to be a non-destructive method for heavy metal assessment. The results revealed the presence of 13 elements, including Mg>Ca>Fe > Zn >Cr>Mn> Ni>Cu>Pb> Co>Cd>Se>V from the feather samples. These findings underscore the potential for migratory seabirds with generalist foraging behaviours to be bioindicators of heavy metal dispersion in aquatic environments. Their preference for locally restricted food sources is the primary source of heavy metal accumulation in the body tissues. This study serves as a case in point, illustrating how local environments and human activities can shape the behaviour of migratory species, particularly those with versatile foraging habits, and how these groups could offer insight into the species’ health and fluctuations in contaminant levels within coastal environments.