Ruby-crowned Tanagers are most active around sunrise than later in the morning (Esquivel and Peris 2008). They mostly forage in pairs but have also been noted to forage alone or in groups (Isler and Isler 1987, Ridgely and Tudor 2009). They have a restless, frequent movement with short flights around foraging areas (Mitchell 1957). They frequently display by flitting their wings to show white underwing coverts (Isler and Isler 1987). In a display of excitement, the males will lift their crest showing their scarlet crown (Isler and Isler 1987). Ruby-crowned Tanagers have been noted to scare off other birds visiting a mimosa tree in order to hoard the sweet excretion of plant lice (Sick 1993).
In the genus Tachyphonus a male will show courtship towards a female or superiority towards another male by repeatedly opening and closing it’s wings to show the white underwing coverts (Sick 1993). The Ruby-crowned Tanager will also raise its crest in order to show its scarlet crown (Sick 1993).
Social and interspecific behavior
These birds are mostly seen in pairs but can be seen singly or in family groups of three or four (Ridgely and Tudor 2009, Isler and Isler 1987). They have sometimes been seen in bigger aggregations but rarely in mixed-species flocks (Isler and Isler 1987). For example, they were recorded in only 17 of 523 mixed species flocks near São Paulo (Develey and Peres 2000), in <4% of flocks from southeastern Brazil (Maldonado-Coelho and Marini 2000), and in only 13% of flocks (4 of 30 flocks) in western Brazil (Ghizoni Jr. 2009). However, they were reported in 26% of mixed flocks (12 of 45 flocks) from Santa Catarina Island, Brazil (Ghizoni Jr. et al. 2006). They were recorded in a flock with 13-plus species in Itatiaia, Brazil in July of 1952 (Mitchell 1957), including Squirrel Cuckoo (Piaya cayana), Maroon-bellied Parakeet (Pyrrhura frontalis), White-browed Woodpecker (Piculus aurulentus), Planato Woodcreeper (Dendrocolaptes platyrostris), Black-and-gold Cotinga (Tijuca atra), Blue Dacnis (Dicnis cayana), Tropical Parula (Setophaga pitiayumi), Fawn-breasted Tanager (Pipraeidea melanonota), Rufous-headed Tanager (Hemithraupis ruficapilla), and Magpie Tanager (Cissopois leveriana). They may accidently enter a flock when attracted by the same food (Davis 1946), for example, the were recorded as one of many frugivorous species attracted to a fruiting Alibertia myrciifolia (Muscat et al. 2014). A literature review of 11 studies found that their frequency of occurence in mixed species flocks was 0.243 (Brandt 2008).
They have also been recorded engaged in aggressive encounters. At flowering Cecropia, they chased White-bearded Manakins (Manacus manacus) and Rufous-bellied Thrushes (Turdus rufiventris), and were chased by Sayaca Tanagers (Thraupis sayaca) and Rufous-bellied Thrushes (Marcondes-Machado and Olivera 1987). Aggressive interactions have also been recorded with White-shouldered Fire-eyes (Pyriglena leucoptera) over flushed prey at army ant swarms (Martin and Ghalambor 2014).
We were not able to find published documentation of predation. However, they are attracted to vocalizations of the Ferruginous Pygmy-owl (Glaucidium brasilianum), which is a likely predator (de Cunha and Vasconcelos 2013). They were also documented as the nosiest member of a bird assemblage mobbing an adult Jararaca Lancehead (Bothrops jararaca), calling persistently (Sazima 2015). Scavengers on Ruby-crowned Tanager corpses include the coprophagous scarab Canthon quinquemaculatus (Cantil et al. 2014).