Ambitious renewable energy targets in many countries has led to the proposed installation of several thousand wind turbines throughout coastal areas of Europe. These are often located on offshore sandbanks, overlapping with important habitats for many seabird species. Potential displacement to avoid offshore wind farms may have energetic consequences for seabird individuals. However, at present there is a paucity of data linking energetic changes associated with displacement, in part, due to a lack of suitable technology for measuring energy expenditure in free-ranging seabirds. A method that is used widely in human research to provide real-time measurements of energy use is near-infrared spectroscopy (NIRS). Here, we describe the initial development and deployment of a NIRS logger to measure muscle oxygen saturation (SmO2) in European shags (Phalacrocorax aristotelis). The NIRS logger was adapted from an existing wearable NIRS system for humans and was deployed on two free-ranging shags on the Isle of May, Scotland during the summer of 2019. Upon retrieval, both loggers were in good condition and did not suffer water ingress or damage during the deployment. However, only one logger recorded data (02h 16m 30s) and, although the NIRS system did collect biologically relevant SmO2 measurements, the duration of viable data was relatively short (~15 mins). Nevertheless, this study demonstrates the first use of a non-invasive NIRS sensor to measure energy expenditure in free ranging seabirds and provides the first noninvasive muscle oxygen measurements in a free-ranging wild animal. It therefore provides the first successful steps in the development of a new technology for measuring high resolution changes in energy expenditure in free-ranging seabirds.