Geographic range estimates and environmental requirements for the harpy eagle derived from spatial models of current and past distribution

Understanding species-environment relationships is key to defining the
spatial structure of species distributions and develop effective
conservation plans. However, for many species this baseline information
does not exist. With reliable presence data, spatial models that predict
geographical ranges and identify environmental processes regulating
distribution are a cost-effective and rapid method to achieve this. Yet
these spatial models are lacking for many rare and threatened species,
particularly in tropical regions. The harpy eagle (Harpia harpyja) is a
Neotropical forest raptor of conservation concern with a continental
distribution across lowland tropical forests in Central and South
America.Currently the harpy eagle faces threats from habitat loss and
persecution and is categorised as Near-Threatened by the International
Union for the Conservation of Nature (IUCN). Within a point process
modelling (PPM) framework, we use presence-only occurrences with climatic
and topographical predictors to estimate current and past distributions
and define environmental requirements using Ecological Niche Factor
Analysis. The current PPM prediction had high calibration accuracy
(Continuous Boyce Index = 0.838) and was robust to null expectations (pROC
ratio = 1.407). Three predictors contributed 96 % to the PPM prediction,
with Climatic Moisture Index the most important (72.1 %), followed by
minimum temperature of the warmest month (15.6 %) and Terrain Roughness
Index (8.3 %). Assessing distribution in environmental space confirmed the
same predictors explaining distribution, along with precipitation in the
wettest month. Our reclassified binary model estimated a current range
size 11 % smaller than the current IUCN range polygon. Paleoclimatic
projections combined with the current model predicted stable climatic
refugia in the central Amazon, Guyana, eastern Colombia, and Panama. We
propose a data-driven geographical range to complement the current IUCN
range estimate, and that despite its continental distribution this
tropical forest raptor is highly specialized to specific environmental
requirements.