Plasticity and overlap of trophic niches in tropical breeding Laridae

Abstract

Trophic ecology of seabirds in tropical regions remains poorly understood despite the large number of multispecies breeding colonies supported by these ecosystems. Here, we used the isotopic niche (δ15N and δ13C) of 5 Laridae species at 2 breeding areas in Cuba to analyze the plasticity and interspecific overlap of trophic niche determined from chick down and feather samples. The down samples reflected the female trophic regime before laying, while the feather samples incorporated the trophic regime of the chicks provided by the parents during rearing. Two main species groups were identified by their isotopic niche characteristics: species with small and quite stable isotopic niches (trophic specialists) and species with large and highly variable isotopic niches (trophic generalists). Laughing gull Leucophaeus atricilla, royal tern Thalasseus maximus, and sandwich tern T. sandvicensis were the generalists and showed significant isotopic niche differences between breeding areas and phases. Bridled tern Onychoprion anaethetus and roseate tern Sterna dougallii were trophic specialists, but only the former exhibited significant variations in isotopic niche breadth between breeding phases. Overall, trophic (inferred from isotopic) niche overlap was relatively low, suggesting that these tropical seabirds reduce competition through niche partitioning. We concluded that trophic niche plasticity and segregation appear to constitute an important adaptive strategy to ensure the breeding success of sympatrically breeding Laridae in north-central Cuba.