Aerial surveys of seabirds: the advent of digital methods

1. Aerial seabird surveys are often conducted so that changes in abundance may be monitored. For example, large-scale offshore wind farms are proposed for UK waters, and surveys are currently being conducted to quantify numbers and distribution ahead of construction. 2. Technological advances mean that strip transect surveys may now be conducted, using digital methods. We address survey design and data analysis issues for such digital surveys, contrasting them with visual aerial line transect surveys. 3. We also explore the relative performances of the methods for estimating the size of a large aggregation of common scoters in Carmarthen Bay, Wales. We found that abundance estimates from two digital methods were closely comparable, while estimates from visual aerial surveys were appreciably lower. 4. Synthesis and applications. Efficient survey methods to quantify abundance and distribution of seabirds are needed, to assess change arising from climate change, or developments such as the construction of large-scale offshore wind farms. The traditional survey methods are visual surveys conducted along transects from ships or aircraft. Digital video and stills surveys can be conducted from aircraft flying sufficiently high to avoid disturbance, while still being able to detect and identify seabirds. Given the rapid technological developments, we expect digital surveys largely to replace visual surveys for seabirds in offshore regions.