The adaptive modulation hypothesis posits that the expression of digestive proteins should
be modulated in response to intake of their respective substrates. A corollary of this
hypothesis suggests that dietary flexibility and digestive plasticity should be correlated. We
examined these two hypotheses in two gra-nivorous Chilean birds (Zonotrichia capensis
and Diuca diuca) that differ in dietary breadth. D. diuca is a strict granivore, whereas Z.
capensis also eats insects. In field-caught birds, the activity of the intestinal dipeptidase …

The adaptive modulation hypothesis posits that the expression of digestive proteins should
be modulated in response to intake of their respective substrates. A corollary of this
hypothesis suggests that dietary flexibility and digestive plasticity should be correlated. We
examined these two hypotheses in two granivorous Chilean birds (Zonotrichia capensis and
Diuca diuca) that differ in dietary breadth. D. diuca is a strict granivore, whereas Z. capensis
also eats insects. In field-caught birds, the activity of the intestinal dipeptidase …