Marine renewable energy developments (MREDs) are becoming an increasing feature of the marine environment. MREDs are just one of several human activities in the marine environment that have the potential to impact marine species. Scotland has considerable potential for generating energy from the marine environment in the form of extensive wind, wave and tidal-stream resources. Scotland also hosts numerous internationally important breeding populations of seabirds and Scottish territorial waters represent a key overwintering area for many species. Several MRED sites in Scotland are located in proximity to Special Protection Areas (SPAs) and draft marine SPAs designated specifically to safeguard important populations of seabirds. EU legislation requires that MREDs do not damage the integrity of protected seabird populations within SPAs. However, the potential effects of MREDs on seabirds are not yet fully understood. In this thesis, I aim to address gaps in knowledge regarding how MREDs may affect seabird populations. Firstly, I generate vulnerability and confidence indices to predict the effects of offshore wind, wave and tidal-stream renewable energy on Scottish seabird populations, and identify areas lacking in data. I found that effects of MREDs are species-specific and several species require additional research and monitoring to confidently predict how MREDs may affect their populations. One Scottish species identified as lacking in data is the great skua Stercorarius skua. Therefore, this thesis investigates the overlap of breeding great skua movements with MREDs. I found that overall overlap with MREDs was low, and that breeding birds and birds that had failed in their breeding attempt differed in their movements at sea. This indicates that subsections of great skua populations could be differently affected by MREDs. To further explore the potential for differential effects of MREDs within seabird populations, I investigate individual variation in great skua foraging behaviour and strategies. I also identify marine environmental conditions influencing great skua foraging behaviour. I found evidence for consistency in individual great skua foraging behaviour and preferred foraging habitat, which indicates that individual behaviour, in addition to breeding status, could lead to subsections of great skua populations being differently affected by MREDs. This section of the thesis illustrates the importance of improving our understanding of both population and individual-level responses to the marine environment in order to more fully understand seabird behaviour and accurately predict potential effects of human activities at sea. Finally, I focus on another area identified as lacking in information in my vulnerability and confidence indices; the use of high current flow environments by seabird species. I use land-based vantage-point surveys to investigate seabird interactions with fine-scale habitat in a leased tidal-stream renewable energy site in Scotland. I found low numbers of diving seabirds foraging in current speeds overlapping with optimal energy generating locations but that auk species and shags are most likely to be vulnerable to effects of tidal-stream renewable energy developments. Overall, this thesis indicates that seabird responses to MREDs are likely to be species-specific and will vary dependent on the development location and design of the energy generating technology. My findings indicate that effects of MREDs will differ dependent on individual foraging strategies, age and life stage of individuals, which implies that MREDs will differently affect subsections of seabird populations.