In a study of territorial communication distance of hooded crows we find an excellent correspondence between model predicted crow call transmission and re-recorded crow calls. Modeling average transmission characteristics within a spatial matrix of sender/receiver distances and heights representative of crow territorial communication and taking into account ground effect and air turbulence, we predict an optimal transmission frequency range between 0,5-1.6 kHz. In a natural open field crow habitat we measure, with sender and receiver heights of 2.8 m and transmission distances up to 320 m, an optimal frequency range between approximately 500 Hz and 2 kHz. The hearing system of crows enables the most sensitive detection of signals in noise within this range. From modeling, noise measurements, and hearing data we estimate hooded crow active space to be roughly 1 km, but with great variance. Discussing a number of other factors in hooded crow communication we conclude that they are highly adapted to communication over the distances and terrain of interest. We suggest that turbulence does not attenuate sound signals appreciably as previously assumed. Finally, we advise against using only composite measures of sound degradation during transmission without taking the ground effect into account.
Sound communication; active space; transmission modeling