Those exploiting pelagic prey could require specific combinations of bathymetry, topography and hydrodynamics to force items towards the sea surface, into dense aggregations or restrict their movement; all of which would reduce energetic costs associated with deep dives and lengthy prey pursuit [11], [14] and [43]. In addition to these broad differences, subtle variations could also occur among populations exploiting similar prey items. For example, three species of planktivorous Auks exploiting

a tidal pass in North America favoured micro-habitats characterised see more by different hydrodynamic conditions [88]. These differences in micro-habitat selection could drive both temporal and spatial segregation among species exploiting tidal passes due to the highly heterogeneous nature of these habitats [12]. Several studies have already documented spatial and temporal segregation among species within tidal passes [12] and [14]. It therefore seems that spatial overlap at the micro-habitat scale varies among populations and within populations over short time periods; with individuals perhaps more vulnerable during certain tidal conditions. Design diversity [5] and [7] alongside issues concerning efficiency GSK-3 beta pathway and accessibility (Section 2.1) means that the micro-habitat occupied or created near devices varies

considerably among installations [89]. As a result, different populations could be vulnerable to different installations. Therefore, predicting spatial overlap at these scales requires comparisons between the micro-habitats favoured by vulnerable species and that found around each installation [89]. The micro-habitats around each installation are

usually known by tidal stream turbine companies due to extensive monitoring before and after installations [1]. In contrast, species favoured micro-habitat have not been quantified beyond a few physical conditions such as tidal speeds [14] and visible surface features [12], conditions that may be shared by several micro-habitats within tidal passes. As tidal stream turbines could occupy very specific micro-habitats within tidal passes, the precise combination click here of physical features underlying a species favoured micro-habitat need to be quantified. At these scales, surveys recording seabirds foraging distributions need to cover as many different micro-habitats within a tidal pass as possible. This is best achieved by not only covering many different areas within these habitats, but also repeatedly sampling the same areas over entire tidal cycles to account for changes in either the location or presence of micro-habitats caused by variations in current speeds and directions [12], [14] and [43]. They also need to discriminate between foraging and non-foraging individuals. Surveys fulfilling these criteria are scarce within the literature [12], [14] and [90]; however, several methods are described below.