Abstract
This is the dedicated interim report concerning WP2 of this project, which deals with methodological review and development. The task of apportioning overlapping components of usage belonging to different colonies and breeding stages of seabirds is not possible from telemetry data alone (because generally only adults are tagged) and very difficult with survey data (because it is hard to tease apart overlapping surfaces with unknown characteristics). However, it should be possible if both data types are combined into a joint analysis. We review the challenges and current methodologies involved in data integration and usage apportioning in seabird species. The task presents two methodological challenges. First, the existing analysis frameworks for telemetry and surveys are not compatible (i.e., the interpretations of their estimates differ). We adopt recent contributions we have made to the statistical literature that bridge this gap. Second, there has been no software implementation of these theoretical advancements into a framework that can deal with multiple overlapping surfaces, corresponding to colonies and ages (adults v juveniles). We present the principles and illustrative examples of the R package TrackTrans, developed for this project. Throughout, we discuss the motivation, remit and methodology for jointly analysing telemetry and survey data and propose possible extensions. We find that the framework leads to inferential improvements compared to the survey-only, or telemetry-only analyses. We finally discuss and present illustrations of marine usage apportionment, based on this methodology.