"Spshing noise": biological significance of its attraction and nonattraction by birds.
Many New World passerine birds, especially migrants which join mixed flocks of local species in the Neotropics, are attracted to a noise termed "spshing" used by humans to attract birds into view. The noise is effective because it mimics the vocalizations of certain bird species which play a central bonding role in mixed species flocks. Migrants join these flocks to gain local expertise about food sources and/or potential enemies in unfamiliar environments. Old World passerine migrants do not react to "spshing." In Africa, they do not join mixed flocks of local species because of more favorable environmental conditions negating the need to do so. In tropical Asia, many migrants join mixed flocks but the local bonding species give vocalizations unlike those of their counterparts in the Neotropics, and thus not like "spshing."
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Smithsonian Tropical Research Institute, P.O. Box 2072, Balboa, Canal Zone.