In resident Amazonian mixed-species flocks, the pattern of attraction of transient species to nuclear Dusky-throated Antshrikes (Thamnomanes ardesiacus) and Long-winged Antwrens (Myrmotherula longipennis) and the pattern of heterospecific attraction between the nuclear species are undocumented. Patterns of attraction can help elucidate the nature of interspecific relationships (i.e., whether they are mutualistic, commensal, or parasitic). We played Dusky-throated Antshrike and Long-winged Antwren vocalizations to flocks and recorded how many transient species approached the playbacks, whether the antshrikes and antwrens were attracted to each other's playbacks, and how strongly they responded to the playbacks. More transient species were attracted to the antshrike vocalizations than antwren vocalizations, and more transient species were attracted to antwren than control vocalizations. Dusky-throated Antshrikes and Long-winged Antwrens approached each other's playback significantly more often than they approached control playbacks; the antwrens responded significantly more strongly to antshrike vocalizations than the antshrikes did to antwren vocalizations. Species may be more attracted to Dusky-throated Antshrikes because of their reliable alarm calling, whereas species may be attracted to antwrens because they serve as a flock indicator. Finally, Dusky-throated Antshrikes and Long-winged Antwrens likely confer benefits to each other, but those benefits may not be symmetrical.

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