How high do birds fly? A review of current datasets and an appraisal of current methodologies for collecting flight height data: Literature review

The consideration of flight heights is a key factor determining how seabirds interact with offshore wind farms. Of particular interest is the need to accurately predict flight heights, in order to feed into predictive Collision Risk Models (CRM). Data within CRM have traditionally relied quite heavily on boat surveys collected by observers, but now routinely, different methods are being used to estimate flight heights of birds.

To date, the relative suitability of methods for the collection of flight heights has not been rigorously appraised. For marine birds, this has primarily included visual methods from boat-based surveys, but more recently remote monitoring techniques such as high definition aerial imagery (images, video and spectrographic techniques) have been used.  Alternative methods have also included bird-borne telemetry, radar, laser rangefinders, thermal imagery and acoustic methods, but their suitability to obtain reliable flight height distributions for potential use within CRM has not yet been assessed. This report details and compares each method for estimating flight heights, evaluating the relative merits and disadvantages of each method.