RESUMEN
BACKGROUND: The drivers of space use patterns of multi-species groups have been poorly studied, although mixed-species avian flocks are common throughout the world. In a mixed-species flock, multiple species move together and maintain proximity. The different species may or may not have conflicting preferences of space use. We hypothesized that the space use patterns of the flock are driven by a single species. METHODS: We investigated the behavioral drivers of space use patterns of mixed-species flocks in Amazonian Peru by mapping 95% fixed-kernel home ranges of three flocks, which then we divided into high-use (inner 55% kernel utilization distribution) and low-use areas (lying outside the high-use area). We quantified the foraging and anti-predator behavior of individual birds in the flocks. We tested whether foraging and anti-predator behavior of different species were different in high use and low use areas of the flock. RESULTS: We collected 455 spatial points and 329 foraging and anti-predator behavior observations on three flocks. The single best model for explaining the space use patterns of the flocks contained only vegetation density that surrounded Dusky-throated Antshrikes. CONCLUSION: The results are consistent with the hypothesis that a single species in mixed-species flocks has a disproportionately large influence on space use patterns. The surrounding vegetation density of the Dusky-throated Antshrike was the only driver of space use patterns of flocks supported by our data. The results may apply to flocks pantropically, many of which are led by species that behave similarly to the Dusky-throated Antshrike, e.g. Asian flocks led by drongos (Dicrurus spp.).
RESUMEN
Predation risk has played an important role in primate behavioral evolution, yet natural primate-predator interactions are rarely observed. We describe the consumption and probable predation of an adult bald-faced saki monkey (Pithecia rylandsi) by a black-and-white hawk-eagle (Spizaetus melanoleucus) at the Los Amigos Biological Station in lowland Amazonian Peru. To our knowledge, this is the first published case of a black-and-white hawk-eagle consuming any primate species. We contend that while most reported observations of successful and attempted predation by raptors involves the largest and most notorious species (i.e. the harpy eagle), smaller and lesser known species like S. melanoleucus should be considered more seriously as a predator of neotropical primates. We discuss the predation event in the context of understanding what other neotropical primates might be vulnerable to S. melanoleucus predation given its body size and hunting tactic.