Seabird and marine mammal observations collected across four RV Prince Madog cruises in the Irish Sea between June 2022 and August 2023.

This dataset contains seabird and marine mammal observations collected across four research cruises in the Irish Sea between 2022 and 2023. Observations were performed using the European Seabirds At Sea (ESAS) methodology, from the RV Prince Madog, between June 2022 and August 2023. For each observation, the species, number and distance band was recorded, along with whether animals were sitting, flying, swimming or foraging. If foraging, the particular foraging behaviour was noted. If flying seabirds were observed, the compass direction was recorded, along with whether the observation was recorded using a 'snapshot' count. Estimates by the observer are also included, such as the sea state (estimated on the Beaufort scale), percentage of the sea surface impacted by intense glare, visual range (distance in m, km or 'horizon') and rainfall intensity. The date, time, latitude, longitude, distance travelled and number of sides scanned are also included in the dataset. The data have been scrutinized for errors and discrepancies. No analyses or processing has been applied. These data were generated by scientists at Bangor University and Heriot-Watt University under 'The impact of the physical environment on the foraging energetics of shearwaters and the consequences for breeding success' (SHEAR), a project funded by the Natural Environment Research Council (NERC) under reference NE/W001217/1.