Researchers have shown that Yellow-legged Gulls are more likely to predate chicks if humans or dogs have caused disturbance, after in-depth observations conducted from a mobile hide.
Ground-nesting birds have a suit of adaptations and behaviours that protect eggs and young from predation. A team led by Mohamed Ali Chokri, from Gabès University in Tunisia, set out to investigate the impact of human-related disturbance on these protections against predation.
Yellow-legged Gulls took more opportunities to target chicks when dogs or humans entered the breeding colony (John Nadin).
The researchers studied a colony of Slender-billed Gulls in Sfax Salina, Tunisia, during the breeding season from a mobile hide. They recorded every case of attempted predation of chicks by Yellow-legged Gulls, noting whether or not there was any disturbance by humans or dogs.
The data revealed that disturbance resulted in increased predation pressure. Yellow-legged Gulls were more likely to attempt to take young Slender-billed Gulls following a disturbance event. The team found the effect particularly pronounced when stray dogs entered the colony, probably because the chicks regard dogs as potential predators, so react differently compared to when humans enter the area.
Overall, they found that predation attempts decreased as the Slender-billed Gull chicks grew older, whether or not disturbance was being conducted.
Reference
Chokri, M A, Hamza, F, Bennour, C, Almalki, M, & Besnard, A. 2023. Disturbance-dependent Yellow-legged Gull (Larus michahellis) predation on Larid chicks decreases with chick age. IBIS. DOI: 10.1111/ibi.13122.
