A comparative study of digestion in North Atlantic seabirds

We present data on digestive efficiencies and gut retention times of eight North Atlantic seabird species, fed on two fish species - lesser sandeel Am modytes marinus and whiting Merlangius merlangus - which commonly occur in the diet of wild seabirds. In an interspecific comparison, there was a posi tive relationship between retention time and digestive efficiency, which we suggest represents a trade-off between conflicting benefits of efficient d igestion and rapid digestion. Analysis of excretion curves revealed that re tention time of digesta in the stomach uas more important than passage time of digesta through the intestine in determining whole gut retention time. Differences in stomach retention time of lesser sandeel and whiting explain ed the longer overall retention time of the latter diet. Stomach retention time and whole gut retention time were greater in species with relatively l arge stomachs, while intestine passage time was correlated with relative in testine length. Species which typically eat a wide range of food types, inc luding low quality items, tended to have slow and efficient digestion and h eavy stomachs, whereas species which specialise on readily digestible and e nergy dense food types had the opposite digestion strategy.