The behavior of Collared Crescentchest is not known in any detail. Crescentchests in general are terrestrial or working through the lower branches of shrubs, generally remaining mostly concealed in grassy cover. May move tail from side to side, holding it slightly open (Sick 1993).
At one site in São Paulo, Brazil (near the edge of the range of this species), the population density was estimated as 4 individuals/km2 ± 0.8 in parque cerrado, and 3 individuals/km2 ± 0.6 in more open grassland habitats (campo limpo and campo sujo) (Kanegae 2012).
Undescribed; presumably is at least socially monogamous.
Social and interspecific behavior
Collared Crescentchest usually is solitary or in pairs.