Effect of high aluminum consumption on mechanics and composition of furculae of free-ranging coots

High levels of ingested Al can affect mechanical properties of bones. Becau se of the spring action of the Furcula during the wingbeat, small changes i n the mechanical properties of this bone may have measurable impacts on lon g-distance flight. We examined the Furculae and ingesta of free-ranging Ame rican coots (Fulica americana) in San Francisco Bay (California, USA), wher e they consume a diet high in Al. We measured the spring stiffness and phas e angle (delta) of the furculae and the concentrations of Al, Ca, F, Mg, an d P in both the furculae and ingesta. The ingesta had mean Al concentration s (2,383 mu g/g, dry weight) and AI:P molar ratios (6.4:1) predicted to aff ect bone integrity but the bone concentrations of Al were near the normal r ange and the furcula stiffness did not change with Al concentration. The ta n delta of the furculae changed with Al concentration but the relationship was weak. The chemical speciation of the ingested Al may have affected its physiologic role and the high mean levels of ingested calcium (71,283 mu g/ g. dry weight) very likely neutralized the activity of the AL. Controlled f eeding studies have shown that F strengthens avian bones. The bones in our study had molar concentrations of F more than two orders of magnitude great er than Al (170:1) but F appears to have insignificant influence on bone me chanics. The coots in San Francisco Bay apparently are not suffering furcul a impairment despite a diet high in Al.