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 Ammodytes marinus and whiting Merlangius merlangus - which commonly occur in the diet of wild seabirds. In an interspecific comparison, there was a positive relationship between retention time and digestive efficiency, which we suggest represents a trade-off between conflicting benefits of efficient digestion and rapid digestion. Analysis of excretion curves revealed that retention 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 explained the longer overall retention time of the latter diet. Stomach retention time and whole gut retention time were greater in species with relatively large stomachs, while intestine passage time was correlated with relative intestine length. Species which typically eat a wide range of food types, including low quality items, tended to have slow and efficient digestion and heavy stomachs, whereas species which specialise on readily digestible and energy dense food types had the opposite digestion strategy.