Testing chemical markers on granivorous birds.

Abstract

We tested two substances (oxytetracycline and rhodamine B) that can be added to food or water of free-living birds, and serve as markers in their plumage for later identification. Oxytetracycline produced no detectable changes in the plumage of red bishops or redbilled queleas. Rhodamine B fed to captive birds produced fluorescence in the wing feathers when viewed under ultraviolet light. This fluorescence lasted for at least 14 weeks, and was retained until feathers were moulted. Rhodamine B may thus be useful in identifying birds using a specific feeding site, and for studies of moult and feather growth.