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.