How are the bills of seed-eating pigeons different from those of fruit-eating pigeons?

The shape of a pigeon's bill is closely associated with its specific feeding habits. These differences are characterized as follows:

• Seed-eating pigeons: These species typically possess slender bills, which are well-suited for their diet of seeds.1
• Fruit-eating pigeons: These birds generally have deeply hooked bills. This adaptation is particularly pronounced in species such as Treron, which feed on large, hard fruits like figs.1

Beyond these external differences, there are internal physiological adaptations that support these distinct diets. Fruit-eating pigeons usually have a broad, short intestine, allowing them to void the stones of the fruits they consume intact. In contrast, seed-eating pigeons possess stronger gizzards and long, narrow intestines to process their food.1