CIE Spotlight: Time-in-area represents foraging activity in a wide-ranging pelagic forager

John A.
John A.

Title: Time-in-area represents foraging activity in a wide-ranging pelagic forager

Authors: Warwick-Evans, V.; Atkinson, P. W.; Gauvain, R. D.; Robinson, L. A.; Arnould, J. P. Y.; Green, J. A.

Source: MARINE ECOLOGY PROGRESS SERIES, 527 233-246, MAY 7 2015

Brief summary of the paper: Successful Marine Spatial Planning depends upon the identification of areas with high importance for particular species, ecosystems or processes.

For seabirds, advancements inbiologging devices have enabled us to identify these areas through the detailed study of at-seabehaviour. However, in many cases, only positional data are available and the presence of localbiological productivity and hence seabird foraging behaviour is inferred from these data alone,under the untested assumption that foraging activity is more likely to occur in areas where sea-birds spend more time.

We fitted GPS devices and accelerometers to northern gannets Morusbassanusand categorised the behaviour of individuals outside the breeding colony as plungediving, surface foraging, floating and flying.

We then used the locations of foraging events to testthe efficiency of 2 approaches: time-in-area and kernel density (KD) analyses, which are widelyemployed to detect highly-used areas and interpret foraging behaviour from positional data. For KD analyses, the smoothing parameter (h) was calculated using the ad hoc method (KDad hoc), and KDh=9.1, where h= 9.1 km, to designate core foraging areas from location data.

A high proportionof foraging events occurred in core foraging areas designated using KDad hoc, KDh=9.1, and time-in-area. Our findings demonstrate that foraging activity occurs in areas where seabirds spend moretime, and that both KD analysis and the time-in-area approach are equally efficient methods forthis type of analysis.

However, the time-in-area approach is advantageous in its simplicity, and inits ability to provide the shapes commonly used in planning. Therefore, the time-in-area approachcan be used as a simple way of using seabirds to identify ecologically important locations fromboth tracking and survey data.