Many parts of the tropical oceans appear to be relatively seasonless,
but, because of the difficulty of sampling mobile and patchily distributed animals
and the cost of oceanographic investigations, few data are available on the extent
of seasonal changes. By regularly collecting regurgitations from sea birds, and
identifying and measuring the food items, seasonal data could be obtained on the
availability, size classes, and perhaps reproductive cycles of the fish and squid characteristic
of the surface layer of tropical seas. Flying fish (Exocoetidae), juvenile
tunas (Scombridae), and squid of the family Ommastrephidae are especially easily
obtainable.
Experience gained during a recent study of the comparative feeding ecology of
sea birds on Christmas Island (Pacific Ocean) makes it possible to assess the characteristics
of bird species which affect their suitability for such study. Potentially
useful species include terns (especially Sterna fuscata, Anous stolidas, A. tenuirostris,
and Gygis alba) and boobies (especially Sula Sula). Samples could be obtained from
several bird species in the same period, and a program could include sampling of
inshore waters with the neuston net and making basic oceanographic observations.
Investigations of this kind could be carried out economically on any of a large number
of tropical oceanic islands