Table 8. Qualitative comparisons among adult humeri.
| Taxon | Cross-sectional shape | Presence of ICL and OCL | Composition of middle cortical layer | Relative vascular density | Primary vascular orientation |
|---|---|---|---|---|---|
| California Quail1 (Callipepla californica) |
circular to ovate | yes; OCL thicker (~1/3 of cortex) but ICL more distinct | woven/incipient fibrolamellar | moderate | longitudinal |
| Wild Turkey1 (Meleagris gallopavo) |
rounded triangle | yes; ICL thicker and more distinct | fibrolamellar | high | circumferential/ plexiform |
| Western Gull2 (Larus occidentalis) |
circular | yes; ICL thicker and more distinct | fibrolamellar | high | reticular |
| American Kestrel3 (Falco sparverius) |
circular | yes; equal thickness, ICL more distinct | woven w/simple canals and regional fibrolamellar | moderate | longitudinal/ reticular |
| Red-tailed Hawk3 (Buteo jamaicensis) |
circular | yes; ICL thicker and more distinct | fibrolamellar | high | longitudinal |
| White-tailed Kite3 (Elanus leucurus) |
circular | yes; OCL thicker, ICL more distinct | fibrolamellar bone with regional woven bone w/simple canals | moderate | longitudinal |
| Barn Owl3 (Tyto alba) | circular | yes; equal thickness, ICL more distinct | fibrolamellar | high | reticular/ circumferential |
| Great-horned Owl3 (Bubo virginianus) |
circular | yes; ICL thicker and more distinct | fibrolamellar | high | longitudinal |
| Mourning Dove4 (Zenaida macroura) |
ovate | yes; ICL incipient, OCL 1/3-1/2 cortex | weakly woven with primary osteons (middle layer is of equal thickness to OCL in some areas) | moderate | longitudinal |
| Anna’s Hummingbird5 (Calypte anna) |
ovate (main medullary cavity) | yes; OCL dominates cortex | none | avascular | — |
| Green-cheeked conure5 (Pyrrhura molinae) |
circular | yes (but ICL thin/irregular); OCL thicker | woven bone with primary vascular canals; patches of fibrolamellar | moderate-low | longitudinal |
| House Finch5 (Haemorhous mexicanus) |
circular | yes; OCL is thicker, ~1/3-1/2 of cortex | woven bone with primary vascular canals; patches of fibrolamellar | moderate-low | longitudinal |
Note:
Vascular density in adults was ubiquitously lower than in younger growth stages, thus relative vascular density among adults only is reported here. “Middle cortical layer” refers to the portion of the cortex located between the OCL and the ICL. Descriptions of the ICL as “more distinct” refer to instances in which the ICL is more advanced in development than the OCL, and to the very high level of organization of tissue in this layer (which appears strongly lamellated and has a distinct, high birefringence). Developmental mode is indicated by color number superscript: orange1, precocial; yellow2, semi-precocial; green3, semi-altricial 1; blue4, semi-altricial 2; purple5, altricial.