Another look at MgB2 and YBCO wires.

IN THEIR BREVIA “FLUORESCENT SIGNALING in parrots” (4 Jan., p. 92), K. E. Arnold and coauthors use mate choice experiments to demonstrate that fluorescence in wild-type budgerigars (Melopsittacus undulateus) is probably functional and not incidental. However, there is further evidence to support this hypothesis in the feathers themselves. The green chest feathers of wild-type budgerigars actually reflect negligible “green” wavelengths—rather, blue and yellow reflections are superimposed. They con-