RELIABILITY OF STOMACH TEMPERATURE-CHANGES IN DETERMINING FEEDING CHARACTERISTICS OF SEABIRDS

We examined the accuracy of stomach temperature archival units (STAUs) , which are-typically used to determine feeding activity in marine end otherms, with regard to determination of the time of prey ingestion as well as the number of prey items ingested and their masses, Units wer e deployed in nine species of free-living seabirds, where feeding cond itions were uncontrolled, eight species of captive seabirds, where fee ding conditions could be partially controlled, and in laboratory stoma ch simulations, where variables could be strictly controlled, The qual ity of data obtained on the timing of feeding, the mass ingested and t he number of prey items ingested was subject to two main sources of er ror (i) those induced by changes in animal activity and (ii) those res ulting from the physical form of the STAUs themselves. Animal activity factors considered important included the following: variability in ( a) body temperature, (b) stomach blood perfusion, (c) consistency of s tomach contents and (d) stomach churning and changes in body orientati on, The physical form (size and buoyancy) of the STAU affected the loc ation of the unit within the stomach, and thus the likelihood that ing ested prey comes into contact with the sensor, The timing of prey inge stion can generally be determined accurately; however, considerable er rors in mass estimates can occur if data acquired using STAUs are not critically assessed, An understanding of these sources of errors will allow researchers to construct STAUs appropriate to the species being studied and to analyze data critically so that errors are reduced.