Beak morphology in songbirds is often shaped by feeding ecology. Granivorous species for example, have evolved larger, stronger beaks to crack hard seeds. Song production, however, favours rapid beak movements associated with high trill rates. This creates a functional trade-off between bite force and movement speed. The biomechanical mechanisms underlying this force–velocity trade-off remain unclear but may primarily involve differences in muscle contraction kinetics. We therefore hypothesise that species with higher bite forces exhibit longer contraction and relaxation times in their jaw muscles. To test this, tetanic contraction and relaxation times were measured in vitro for an opener and a closer muscle in five granivorous songbird species. We found that the stronger biting species indeed had slower muscle force kinetics, and especially a longer force rise time, compared to the weaker biters. These differences were more pronounced in the closer muscles. Because muscle contraction kinetics are influenced by fibre type composition, the slower contraction kinetics observed in strong biting species may reflect a greater proportion of slow fibres. Future work will test this by examining fibre type composition in jaw muscles.