MEPS 622:177-189 (2019)  -  DOI: https://doi.org/10.3354/meps13022

ABSTRACT: Competition, predation and facilitation shape community structure. Yet facilitative behaviour is poorly studied, especially in marine ecosystems. We investigated the diet and foraging behaviour of 5 Afro-Palaearctic migratory seabirds during their non-breeding period in West Africa, focussing on their facilitative associations with predatory fishes. We used next-generation sequencing to describe the diet of 5 tern species, employing DNA metabarcoding for the identification of prey from droppings. This is the first time this method has been used for studying the diet of non-breeding migratory seabirds. Our results showed a high diet overlap among all seabirds, mostly due to the dominance of a single prey species, Sardinella maderensis (with a mean frequency of occurrence of 90% in tern diets). The subsurface marine predators identified in association with terns were crevalle jack Caranx hippos and West African Spanish mackerel Scomberomorus tritor, 2 predatory fishes which also rely on Sardinella maderensis as their most frequent prey in the study area, the Bijagós Archipelago. There were marked inter-specific differences in the reliance of terns on subsurface marine predators as facilitators, ranging from completely independent (little tern Sternula albifrons) to near-obligatory (black tern Chlidonias niger). The varied feeding strategies and small-scale spatial segregation may explain the co-existence of the 5 tern species during the non-breeding period, preying mostly on the same clupeids. Declines both in predatory fishes and in Sardinella maderensis and other clupeids are likely to impact the long-distance migrant seabirds studied here, calling for integrated management of fisheries in these coastal ecosystems.

KEY WORDS: Predator-prey interaction · Tern · Next-generation sequencing · DNA metabarcoding · Sympatric predators · Facilitated foraging