More food or fewer predators? The benefits to birds of associating with a Neotropical primate varies with their foraging strategy

Although mixed-species associations of birds or primates have been well studied, primate-bird associations have received comparatively little attention. Additionally, benefits accruing with such associations have rarely been quantified. Over 13 months, 17 insectivorous bird species were observed associating with golden-backed uacaris. Detailed study of four found that feeding sally frequency significantly increased for sit-and-wait foragers (bronzy jacamar, Galbula leucogastra; black-fronted nunbird, Monasa nigrifrons), when uacaris were present within 14.9m, but not when within 15-30m. Contemporaneously, no significant differences were observed in peck bout frequency for two uacari-following bark- and leaf-gleaning antbirds (black-crested antshrike, Sakesphorus canadensis, black-winged antbird, Hypocnemoides melanopogon) when uacaris were present or absent. Antbird/uacari approximation is attributed to significant reductions in the presence of small bird-eating raptors when uacaris are present. Reasons for this are uncertain but may be because large raptors (e.g. harpy eagles) follow uacaris. So, while some bird species may gain foraging benefits from uacari presence, others may follow them because their proximity reduces predation risk. This appears foraging guild dependent. Except for work linking increased jacana peck rates with swamp-visiting gorilla presence, this study is the first to quantify benefits to birds of following primates, and the first such Neotropical study.