An allometric function to fit leg‐loop harnesses to terrestrial birds

Harnesses are indispensable for a long‐term attachment of instruments to animals, particularly birds. The exact fit is crucial for both the reliability of the tags and the animals’ health and natural behaviour. Using data from 19 bird species ranging from 8–400 g, I present an allometric function to calculate the dimension of leg‐loop harnesses for birds on the basis of body mass data. The model greatly facilitates determining the correct loop span for new species without time‐consuming experiments. More importantly, the equation permits calculation of the excess span that is required for tagging juvenile, still growing birds.