ABSTRACT. The role of seed chemical traits (nutrient composition, energy contents and presence of secondary
compounds) for the selection of foods by granivorous birds and for the evolution of bird granivory is analyzed
and compared with the roles of other seed traits such as seed distribution and seed morphology. A literature
review was made, focusing on: 1) seasonal dietary shifts from seeds to other food items; 2) dietary effects of
between-seeds differences in energy and nutrient contents; and 3) dietary effects of seed secondary chemistry.
Results suggest that the effects of seed chemistry on seed-eating bird diets are much less important than the
effects of morphologic naits related to seed processing speed. Birds generally tend to select the food items they
can process faster, their chemical composition being of secondary importance. Several experiments aimed to
test this hypothesis are proposed. This pattern of food selection suggests that the evolution of bird granivory
has been mainly focused on the development of morphologic adaptations for the mechanical digestion of seeds,
whereas physiologic adaptations for their chemical digestion appear to be secondary. Additional data on the
physiology of seed-eating birds in the wild would be necessary to corroborate this idea. COMPB IOCHEMPH YSIOL
113A;3:239-246, 1996.
KEY WORDS. Chemical digestion, diet choices, energy contents, insects, mechanical digestion, nutrient
composition, secondary compounds, seed-eating birds, seeds