Breeding biology of the Critically Endangered Cherry-throated Tanager <i>Nemosia rourei</i>

Summary The “Critically Endangered” Cherry-throated Tanager Nemosia rourei is endemic to the Atlantic Forest of south-eastern Brazil, and extremely rare for reasons that are not yet fully understood. We monitored reproductive activities of the only known individuals of the species, at two sites, between October 2018 and November 2023. The birds foraged in social groups of 5–8 individuals. Ten nests, built in trees at heights of 12–26 m, were monitored through continuous direct observation. Most reproductive activity occurred between October and end of November, with one further nest found in March. Clutch size was 3–4 eggs, the incubation and nestling periods were 16 days, and the chicks were fed mainly on invertebrates. Up to six nest helpers, likely young from previous seasons, assisted with the collection of nest material, feeding the chicks, and defending the nest. Reproductive success was 50%, with losses due to climatic conditions (rain and cold) and predation, but may have been enhanced by the efforts of the researchers in scaring away potential predators including Spot-billed Toucanet Selenidera maculirostris and Black Capuchin Sapajus nigritus. These findings reinforce the value of detailed observation of social groups and their nests, and continuing efforts to deter predators. Further research could address how parental care and nest helpers affect reproductive success. The availability of large trees with abundant lichens may be a limiting factor for the reproductive success of species in the long term, and so protecting and restoring habitat with such features is crucial for the long-term conservation of this species.