Ecology: Deforestation threatens one of the world’s largest eagles

Harpy eagles (Harpia harpyja) – which are among the world’s largest eagle species - struggle to feed offspring in heavily deforested areas of the Amazon, according to a study published in Scientific Reports.

Everton Miranda and colleagues found that harpy eagles rely on specific prey that lives in canopy forests, including sloths and monkeys. Eaglets starved in areas of high deforestation where canopy-based food was limited.

The authors 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. The authors identified 306 prey items, nearly half (49.7%) of which were two-toed sloths, brown capuchin monkeys and grey woolly monkeys. The authors’ observations indicated 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 authors conclude that as breeding harpy eagles rely on specific food and rarely hunt in deforested areas, harpy eagle survival depends on forest conservation.