Loggers affect the foraging behaviour and fitness of European shags

Biologgers enable real-time collection of detailed behavioural and physiological data from wide-ranging animals, including seabirds inhabiting remote regions. However, the number of studies using tracking devices has not been matched by research exploring the behavioural and fitness costs of deployment, and the effects on data reliability. We assessed how GPS loggers, video loggers, and time depth recorders (TDRs) affect the behaviour, physiology, and reproductive performance of European shags (Gulosus aristotelis) breeding on Sklinna, Norway. The loggers varied in mass, attachment location, and deployment duration, allowing comparison of their relative effects. Birds without loggers served as controls to assess logger-related changes in adult body mass, chick growth, reproductive success, and survival. Birds with long-term tail-mounted GPS loggers and leg-mounted TDRs showed altered foraging behaviour, including shorter trips and dives, compared to birds with tail-mounted GPS and TDRs ..., , # Loggers affect the foraging behaviour and fitness of European shags

Dataset DOI: [10.5061/dryad.2z34tmq07](https://doi.org/10.5061/dryad.2z34tmq07)

## Description of the data and file structure

Below are the definitions of each variable included in the six datasets used for the analysis in our paper *“Loggers affect the foraging behaviour and fitness of European shags.”* These descriptions are provided to aid correct interpretation and reuse of the data.

**1. Foraging behaviour (dataset: Foraging_trip.csv)**

| **Variable** | **Definition** |
| :----------- | :--------------------------------------------- |
| trip\_id | Unique ID for each recorded foraging trip |
| sex | Male or Female |
| year | Year |
| TripComp | Trip completed |
| N | Number of GPS locations |
| maxdist | M...,