A simple method for tracking vertebrate-dispersed seeds

Tracking vertebrate-dispersed seeds from parent plant to deposition site remains a primary obstacle to understanding the ecological and evolutionary consequences of seed dispersal. We evaluate a new and simple technique for tracking seeds. Fluorescent microspheres (15 mu m diameter) are applied to fruits and later recovered in fecal material associated with the fruits' seeds. Trials with captive Cedar Waxwings (Bombycilla cedrorum) demonstrated that (1) percentage recovery of microspheres is high, (2) all defecations containing seeds also contain microspheres, (3) relatively few microspheres are recovered in defecations not containing seeds, and (4) presence of microspheres on fruits does not affect fruit choice. Field trials with five species of fruits demonstrated that, after similar to 30 d under full sun and high temperatures, photodegradation limits one's ability to detect microspheres, The field trials also showed that an anti-transpirant applied with the microspheres allows them to adhere to fruits without deterring fruit consumption or damaging fruits and that microspheres can be found in fecal samples of wild birds. Our technique is likely to be applicable to any study in which it is necessary to link fecal material with a particular source of food or an individual animal.