Dataset: bird obs - metadata
Deployment: NH0007

Observed counts of seabirds recorded as flying in a steady direction were adjusted for the effect of flight speed and direction relative to that of the ship (Spear et al., 1992; Spear and Ainley, 1997b). The effect of such flux is the most serious bias encountered during seabird surveys at sea (Spear et al., 2005). Known as random directional movement (as opposed to nonrandom directional movement, which occurs when birds are attracted or repelled from the survey vessel), this problem usually results in density overestimation because most species fly faster than survey vessels; densities of birds that fly slower or at a similar speed as the survey vessel (e.g., storm-petrels), or are flying in the same direction, are usually underestimated (Spear et al., 1992)

Observed counts of seabirds recorded as flying in a steady direction were adjusted for the effect of flight speed and direction relative to that of the ship (Spear et al., 1992; Spear and Ainley, 1997b). The effect of such flux is the most serious bias encountered during seabird surveys at sea (Spear et al., 2005). Known as random directional movement (as opposed to nonrandom directional movement, which occurs when birds are attracted or repelled from the survey vessel), this problem usually results in density overestimation because most species fly faster than survey vessels; densities of birds that fly slower or at a similar speed as the survey vessel (e.g., storm-petrels), or are flying in the same direction, are usually underestimated (Spear et al., 1992)