This study describes the breeding biology, diet, behavior and nest characteristics of Philippine Eagles in Mindanao using data from five Philippine Eagle pairs nesting from 1999 to 2007.
An estimate of longevity for Philippine Eagles was also calculated using information on breeding success spanning three decades (1977-2007). Although results for breeding behavior, diet analysis, and nests and nest tree characterization did not vary considerably from previous studies, this study provides additional details and insights from the parameters considered.
Data show that the Philippine Eagle has the longest and energetically most expensive parental investment for any bird of prey. Baseline values for nest attendance, incubation and brooding bout duration, trip duration and feeding rates during each stage of breeding for each sex were provided. Surface area of nests studied were larger on the average than reported in earlier tests. Flying lemur Cynocephalus volans was the primary prey species, and arboreal mammals constituted the most important prey group.
At least 14 prey taxa were recorded and nine were identified to the species level. Philippine Eagles are opportunistic feeders that can shift their diet to what is available. When heavier, native mammals are scarce, they adjust by taking on smaller prey items at a higher frequency. An explanation for sexual dimorphism in raptors predicts that female takes larger and heftier prey whereas the male preys on smaller, more agile species. The study found no evidence for prey base partitioning among sexes. This study documents the first evidence of predation on domestic animals and pets, and two instances of breeding failures because of food stress.
The fact that the Philippine Eagle lives long, invests a lot on breeding, and that its continuing habitat is lost predisposes the species to extinction. To increase adult survival and ensure productivity, it is important to protect breeding adults and the places where they nest. Conservation of the home range where they hunt is equally important to ensure that enough prey base is available. Community-based conservation (CBC) approaches should be employed in places where people and Philippine Eagle conflicts are tense.