On the relationship between, and measurement of, amplitude and frequency in birdsong

► We address methodological problems in Cardoso & Atwell (2011, Animal Behaviour, 82, 831–836). ► We illustrate common problems with taking acoustic measurements from spectrograms. ► Reliable amplitude measurements require calibrated and controlled recordings. ► We explain the interrelationship of frequency and amplitude in animal vocalizations. ► Bioacoustic studies should consider basic principles of acoustics and proper analysis tools.