Flight tunnel bioassays confirmed attraction of female Caribbean fruit flies, Anastrepha suspensa (Loew), to volatiles from aqueous solutions of avian fecal material and methanol extracts of avian fecal material. Attraction was highest to freshly prepared and 72-h-old solutions of crude material. In direct comparisons between aqueous solutions of crude material and weight-equivalent amounts of methanol extract, more females were captured in response to volatiles from crude material in tests of 0-, 24- and 72-h-old solutions. Ammonia release rate was greater from the crude material than from the methanol extract in tests of 0-, 24- and 48-h-old solutions, The greatest amount (± sd) of ammonia was released from freshly prepared aqueous solutions of crude material (777 ± 250 µg/h from 75 mg of crude material) but dropped within 24 h (288 ± 96 µg/h from 75 mg of crude material) and then stayed close to that level. The greatest amount of ammonia released from methanol extracts was obtained from freshly prepared solutions (229 ± 70 µg/h from 75 mg crude material weight equivalent), also dropped within 24 h (98 ± 12 µg/h from 75 mg crude material weight equivalent) and then stayed fairly constant. Numbers of flies captured by either solution were directly correlated with ammonia release within the first 48 h of testing only, indicating that ammonia was partially or wholly responsible for attraction to the crude material during the first 48 h of testing. An increase in capture of females by volatiles from avian fecal material after 72 h in aqueous solution, which was observed in all tests, indicates that some chemical(s), other than ammonia, remain to be identified that are involved in fruit fly attraction.