| From four visits to Monito Islet in the Isla de Mona Natural Reserve, the prey description (diversity, dominance, importance, length, taxonomy and volume), the dietary niche (breadth, contribution and overlap) and the feeding strategy were studied through regurgitation analysis of three pelagic bird species roosting and nesting in sympatry, and constituting the genus Sula in the West Indies. This population consumed approximately 28,466 organisms (2.4 metric tons or 17 organisms per bird) per day. Food was abundant and the species differed in diets and feeding strategies. The masked booby (S. dactylatra) regurgitated the largest organisms, with a diet dominated by the clearwing flyingfish (Cypselerus comatus ). Both the brown (S. leucogaster) and the red-footed booby (S. sula) were generalists and regurgitated organisms similar in size, mostly mackerel scad (Decapterus macarellus) and the sailfin flyingfish (Parexocoetus hillianus), respectively. At the prey family level, the diets were similar in oligotrophic zones of the Pacific Ocean. Prey volume was highest in visits at breeding peaks, especially in the masked booby. Their diets were similar to the diet reported for dolphinfish (Coryphaena hippurus) in contrast to yellowfin tuna ( Thunnus albacares). The evidence suggests each species feeds from a different resource. The findings have implications in the use of seabirds as indicators of epipelagic fish stock fluctuations. |
