 The nocturnal nesting behaviour of some seabirds has been interpreted as arising due to pressure from this aerial piracy.Kleptoparasitism is not thought to play a significant part of the diet of any species, and is instead a supplement to food obtained by hunting.A study of great frigatebirds stealing from masked boobies estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%.