Supplementary material from "Reconstruction of long-distance bird migration routes using advanced machine learning techniques on geolocator data"

Geolocators are a well-established technology to reconstruct migration routes of animals that are too small to carry satellite tags (e.g. passerine birds). These devices record environmental light-level data that allow to the reconstruction of daily positions from the time of twilights. However, all current methods for analysing geolocator data require manual pre-processing of raw records for eliminating twilight events showing unnatural variation in light levels, a step that is time-consuming and must be accomplished by a trained expert. Here we propose and implement advanced machine learning (ML) techniques to automate this procedure and apply them on 108 migration tracks of barn swallows (Hirundo rustica). We show that routes reconstructed from the automated pre-processing are comparable with those obtained from manual selection accomplished by a human expert. This raises the possibility of automating light-level geolocator data analysis and possibly analysing large amount of data already collected on several species.