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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).