Segregation in Diet between Black Noddy (Anous minutus) and Brown Noddy (A. stolidus) from the Southern Lagoon of New Caledonia

The Black Noddy (Anous minutus) and the Brown Noddy (A. stolidus) occur sympatrically in the Southern Lagoon of New Caledonia, breeding on islets located at the edge of a wide, productive coral-reef lagoon next to oceanic waters enriched by a seasonal upwelling. The diets of the two species were determined from regurgitations from birds nesting at Kouaré Islet during two consecutive breeding seasons (2002/2003 and 2003/2004) and compared. The average prey load in the Brown Noddy was heavier than that in the Black Noddy, as expected from its larger body size and from a predicted longer foraging distance. Fish prey dominated the diet of both species (100% and 81.8% biomass in Black and Brown Noddies, respectively); the remainder consisted of squid. Black Noddy ate small pelagic fishes inhabiting the reef and the lagoon, mainly round herrings (Spratelloides spp.), and Brown Noddy mainly preyed on offshore species including buccaneer anchovy (Encrasicholina punctifer) and larger pelagic fishes (Exocoetidae) and squids. The segregation in diet between Black and Brown Noddies in New Caledonia thus indicated spatial segregation in foraging zones (i.e., inshore versus offshore, respectively), which was more pronounced than previously reported for other sites where the two species co-occur.