We have been the first to investigate whether long-lived geese and ducks can detect and avoid a large offshore wind farm by tracking their diurnal migration patterns with radar. We found that the percentage of flocks entering the wind farm area decreased significantly (by a factor 4.5) from pre-construction to initial operation. At night, migrating flocks were more prone to enter the wind farm but counteracted the higher risk of collision in the dark by increasing their distance from individual turbines and flying in the corridors between turbines. Overall, less than 1% of the ducks and geese migrated close enough to the turbines to be at any risk of collision.

Prenatal exposure to systemic antibacterials is associated with an increased risk of overweight and obesity at school age, and this association varies by birth weight.

European legislation requires Strategic Environmental Assessments (SEAs) of national offshore wind farm (OWF) programmes and Environmental Impact Assessments (EIAs) for individual projects likely to affect birds. SEAs require extensive mapping of waterbird densities to define breeding and feeding areas of importance and sensitivity. Use of extensive large scale weather, military, and air traffic control surveillance radar is recommended, to define areas, routes and behaviour of migrating birds, and to determine avian migration corridors in three dimensions. EIAs for individual OWFs should define the key avian species present; as well as assess the hazards presented to birds in terms of avoidance behaviour, habitat change and collision risk. Such measures, however, are less helpful in assessing cumulative impacts. Using aerial survey, physical habitat loss, modification, or gain and effective habitat loss through avoidance behaviour can be measured using bird densities as a proxy measure of habitat availability. The energetic consequences of avoidance responses and habitat change should be modelled to estimate fitness costs and predict impacts at the population level. Our present ability to model collision risk remains poor due to lack of data on species‐specific avoidance responses. There is therefore an urgent need to gather data on avoidance responses; energetic consequences of habitat modification and avoidance flights and demographic sensitivity of key species, most affected by OWFs. This analysis stresses the importance of common data collection protocols, sharing of information and experience, and accessibility of results at the international level to better improve our predictive abilities.

Since the early 1990s, marine wind farms have become a reality, with at least 13 000 offshore wind turbines currently proposed in European waters. There are public concerns that these man-made structures will have a significant negative impact on the many bird populations migrating and wintering at sea. We assess the degree of usefulness and the limitations of different remote technologies for studying bird behaviour in relation to bird-turbine collisions at offshore wind farms. Radar is one of the more powerful tools available to describe the movement of birds in three-dimensional space. Although radar cannot measure bird-turbine collisions directly, it offers the opportunity to quantify input data for collision models. Thermal Animal Detection System (TADS) is an infra red-based technology developed as a means of gathering highly specific information about actual collision rates, and also for parameterizing predictive collision models. TADS can provide information on avoidance behaviour of birds in close proximity to turbine rotor-blades, flock size and flight altitude. This review also assesses the potential of other (some as yet undeveloped) techniques for collecting information on bird flight and behaviour, both pre-and post-construction of the offshore wind farms. These include the use of ordinary video surveillance equipment, microphone systems, laser range finder, ceilometers and pressure sensors. BIRDS AND OFFSHORE WIND FARMSMigratory bird species enjoy a high public profile and are protected by international and national legislation designed to protect shared natural resources. Hence, migrant birds figure prominently in the environmental impact assessment (EIA) process associated with most wind farm development projects. The coastal and offshore waters of Europe are of global importance for several species of resident and migratory birds. The hazards posed to birds by the construction of offshore wind farms can be summarized under three broad headings: (1) Displacement and flight avoidance responses (birds are displaced from an ideal feeding distribution by the presence of turbines, or avoid flying near to them on migration); (2) Habitat loss/modification (physical habitat loss under foundations, or the creation of novel feeding and resting opportunities that actively attract birds to the turbines); and (3) Collision risk (the probabilities of individuals of different species being struck by turbines).Of these, collision risk will have the most direct impact at the population level, because it elevates the normal mortality rate of species (Johnson et al. 2002). This review will mainly focus on the risk of collisions. However, this does not imply that the other effects are trivial, especially when the cumulative effects of, for example, habitat loss are considered in the light of the construction of many offshore wind farms along the length of a migratory bird species' corridor . DEFINING THE ROLE OF REMOTE TECHNOLOGIESTo support an adequate assessment of the risk presented by each hazard, and subsequen...

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