DAVAO CITY—Government and global raptors’ conservation program are introducing “new spatial methods to conserve the critically endangered Philippine eagle are being used for the first time” to allow greater tracking of the movement of the eagle and help conservationists plot the direction and range estimates of the eagle in the wild.
The new methods would also likely benefit the conservation program for the vulnerable Mindanao bleeding heart pigeon (Gallicolumba crinigera), a bird endemic to the country and could be found only in Mindanao, Basilan, Samar, Leyte and Bohol.
The use of the new method was bared during a recent webinar on Philippine eagle range metrics and spatial conservation planning organized by the Biodiversity Corridor Project, under the Department of Environment and Natural Resources, in partnership with the United Nations Development Programme, and the Global Environment Facility.
The Philippine Eagle Foundation and the Peregrine Fund also sponsored the webinar, which described the new program as “using remote sensing data to model population distribution in Eastern Mindanao Biodiversity Corridor.”
Resource speakers Philippine Eagle Foundation’s Dr. Jayson Ibañez and Peregrine Fund’s Dr. Luke Sutton cited earlier technical reports on space-time home range estimates and resource selection for the national bird, which is one of the biggest raptors in the world.
“For the first time, we determine two important spatial processes for this critically endangered raptor that can help in directing conservation management,” Sutton said, citing the report.
“Rather than employing a single home range estimator, we recommend that analysts consider multiple approaches to animal movement data to fully explore space-time and resource use,” he said.
Sutton said the reports quantified home-range size and habitat resource selection, which he said have been important elements in wildlife ecology, useful for informing conservation action especially for the Philippine Eagle, while many home-range estimators and habitat resource selection functions are currently in use.
“However, both methods are fraught with analytical issues inherent within autocorrelated movement data from irregular sampling and interpretation of resource selection model parameters to inform conservation management,” he pointed out.
Sutton explained: “Here, we apply satellite telemetry and remote sensing technologies to provide first estimates of home-range size and resource selection for six adult Philippine eagles [Pithecophaga jefferyi], using five home range estimators and non-parametric resource selection functions.”
Using space-time autocorrelated kernel density estimate to measure the largest median 95 percent home-range size (68 kms) and a 50 percent core range (13 kms) for the Philippine Eagle, “from the resource selection functions, all adults used areas high in photosynthetic leaf and canopy structure but avoided areas of old growth biomass and denser areas of vegetation, possibly due to foraging forays into fragmented areas away from nesting sites,” he said.
To note, priority conservation areas and a global population estimate for the Philippine Eagle were derived from earlier modelled range metrics using remote sensing habitat characteristics.
The International Union for Conservation of Nature (IUCN) Red List uses three range metrics that define species distributions and inform extinction risk assessments: extent of occurrence, area of occupancy and area of habitat.
“However, calculating all three metrics using standard IUCN approaches relies on a geographically representative sample of locations, which for rare species is often spatially biased,” the report said.
“Here, we apply model-based interpolation using Species Distribution Models (SDMs), correlating occurrences with remote-sensing covariates, to calculate IUCN range metrics, protected area coverage and a global population estimate for the Philippine Eagle, with their final range wide continuous SDM having high predictive accuracy [using Continuous Boyce Index],” the report added.
Sutton said current global population estimate is 352 breeding pairs, or 704 mature individuals across the Philippine eagle global range based on latest inferred habitat.
Sutton is a UK-based ornithologist and montane forest botanist, and together with Ibañez, authored earlier scientific reports on novel processes and approaches on Philippine eagle telemetry and range estimates.
Image credits: BARMM Menre file photo