Figure 2.

The estimated position and orientation of the hummingbird shoulder and proximal forelimb bones through a complete stroke cycle in hovering flight: (a) beginning of downstroke, (b) mid-downstroke, (c) end of downstroke, (d) middle of upstroke. Key to colours: red, humerus; dark blue, ulna; green, radius; magenta, radiale; light blue, ulnare; gold, manus; grey, sesamoid bones; tan, incompletely measured medial and distal elements. The upper row contains a magnified view of the left shoulder while the lower row shows the shoulder girdle and left wing positioned within the silhouette of the bird. All views are from a point slightly above, behind and to the right of the bird. The position of the bones was determined by the marker-based kinematic chain analysis, referenced from their position in the mid-downstroke pose (b), which served as the base orientation in constructing the kinematic chain and was also the pose of the bird in the µCT scan used to generate the bone models.