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Résumé :
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Behaviors of introduced species can change with context and can impact local ecosystems in negative and positive ways. Warbling White-eye (Zosterops japonicus), Red-billed Leiothrix (Leiothrix lutea), and Red-whiskered Bulbul (Pycnonotus jocosus) are introduced species at several locations globally, including O‘ahu, Hawai‘i, where they are responsible for the majority of seed dispersal. To understand how behaviors of introduced species vary across ecological contexts and impact local seed dispersal, it is important to identify the circumstances under which individuals engage in foraging and social behaviors, examine interspecific variation in these behaviors, and compare behaviors across localities. From 2015 to 2017 on O‘ahu, we used radio telemetry to track 68 individuals year-round and conducted 459 behavioral observations to examine how often they forage on specific foods (insects, fruit) and employ specific social behaviors (alone, with a mate, mixed-species foraging aggregation, conspecific foraging aggregation). In their native ranges, these three omnivorous species exhibit social foraging in conspecific or mixed-species aggregations. Here, all species were observed in mixed-species aggregations consisting of only introduced species, suggesting that the behavior of social foraging has been maintained from their native ranges even though the species assemblages are different. All species foraged on fruit and insects on O‘ahu, but P. jocosus shifted away from primarily foraging on fruits during of the breeding season. Thus, L. lutea and Z. japonicus contribute to seed dispersal more consistently throughout the year compared to P. jocosus. All species participated in aggregations outside of the breeding season, and these aggregations primarily foraged on fruit, which suggests the potential for longer distance seed dispersal events outside of the breeding season. These results suggest that flexibility in social and foraging behaviors across the year and across ecological contexts may influence how introduced species integrate into novel communities and impact local seed dispersal.
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