The survival of one of the world’s largest eagle species, Harpy eagles (Harpia harpyja) is under threat. These magnificent birds are struggling to feed offspring in heavily deforested areas of the Amazon. There has been a decline in numbers of breeding pairs by 3,256 since 1985.

Harpy eagles are apex predators and rely on specific prey that lives in canopy forests, including sloths and monkeys. Researchers have found that Eaglets starved in areas of high deforestation where canopy-based food was limited.

The scientists observed prey species, how frequently prey was delivered, and estimated the weight of prey in 16 harpy eagle nests in Amazonian forests in Mato Grosso, Brazil using cameras and identifying prey bone fragments.

They also referenced maps and Google Earth to calculate deforestation levels 3-6km around nests.

They identified 306 prey items, nearly half (49.7%) of which were two-toed sloths, brown capuchin monkeys and grey woolly monkeys.

The results suggest that harpy eagles in deforested areas did not switch to alternative prey, and delivered canopy-based prey less frequently and with smaller estimated weight. In landscapes with 50-70% deforestation, three eaglets died from starvation, and no nests were found in areas with deforestation over 70%.

The authors calculated that areas with over 50% deforestation are unsuitable for harpy eagles to successfully raise offspring and estimate that around 35% of northern Mato Grosso is unsuitable for breeding harpy eagles. This may have caused a decline in numbers of breeding pairs by 3,256 since 1985.

The study is published in Scientific Reports.

restoring harpy eagle population viability within highly fragmented forest landscapes critically depends on decisive forest conservation action.

Tropical deforestation induces thresholds of reproductive viability and habitat suitability in Earth’s largest eagles