Fig. 6. Schematic representation of a cross section through the upper and lower beak of the Java sparrow. (A) In the resting position the lower jaw would press just off centre onto a 2.5 mm seed, generating a force along the surface of the seed. (B) Biting force might be directed more efficiently perpendicular to the surface of the seed by moving the lower jaw in a direction opposite to the side where the seed is cracked (large arrow in A).