Collared Aracari primarily is frugivorous, but, like other toucans, it also consumes large insects and small vertebrates, including eggs and nestlings of other birds. Fruits identified in the diet include Aniba sp., Bursera simaruba, Carica sp. Casearia corymbosa, Casearia nitida, Cayaponia sp. Cecropia, Coussapoa herthae, Dussia sp. Ehretia tinifolia, Ficus padifolia, Guarea glabra, Guarea kunthiana, Humiriastrum procerum, Metopium browneii, Myrica sp., Nectandra guadaripa, Neea psychotrichoides, Ocotea floccifera, Ocotea mollifolia, Phylotacca dioica, Protium glabrum, Renealmia alpinia, Simarouba amara, Talisia oilvaeformis, Trophis sp., Virola dixonii, Virola sebifera, Virola surinamensis, and various palms (including Bactris, Chamaedorea, Iriatea deltoidei, Pholidostachys dactyloides, and Prestoaea) (Howe and Primack 1975, Howe and Steven 1979, Kantak 1979, Howe 1981, Howe and Kerckhove 1981, Trainer and Will 1984, Stiles and Skutch 1989, Berg 2001, Short and Horne 2001, Foster 2007, García-Robledo and Kuprewicz 2009). Most of the fruits eaten in western Ecuador (subspecies erythropygius) were green or burgandy when ripe (Berg 2001). Also occasionally consumes flowers (Pseudobambax) (Berg 2001).
Consumption of insects and other invertebrates may increase when aracaris are feeding nestlings (Skutch 1958). Probably preys on a wide range of bird nests, but specifically has been observed removing or eating eggs or nestlings of Yellow-green Vireo (Vireo flaviroridis), Clay-colored Thrush (Turdus grayi), and Crimson-backed Tanager (Ramphocelus dimidiatus) (Robinson and Robinson 2001).
There probably is little competition with frugivorus migrants, wintering from North America, as the aracari is much larger than the migrants and typically wins out in aggressive confrontation (Leck 1972).