Attributing seabirds at sea to appropriate breeding colonies and populations

摘要: • A key part of the consenting process for proposed marine offshore renewable developments is to establish the colonies of origin of birds that may be affected. The majority of data on seabird distributions are collected through observations from ships or planes, and the connectivity of the observed birds to colonies is unknown. In such cases, the current approach is a calculation that apportions effects such as collision mortality to different colonies based on the distance to each colony and the size of each colony.• This approach assumes that foraging ranges of adjacent colonies overlap. However, segregation between colonies may occur if birds aim to forage close to the colony to minimise travel costs or avoid competition with individuals from other colonies. Thus, the current approach could result in a greater number of colonies apparently affected, whilst segregation could result in fewer colonies affected, but to a greater degree. A further limitation of the current approach is that it does not account for environmental heterogeneity. Furthermore, it assumes that the density of birds increases in relation to the inverse of the square of the distance from the colony (the “distance decay”), and this is predefined and identical for all species, not estimated empirically from data.