Quantifying home range size and habitat resource selection are important elements in wildlife eco... more Quantifying home range size and habitat resource selection are important elements in wildlife ecology and are useful for informing conservation action. Many home range estimators and 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. 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),. CC-BY-NC-ND 4.
bioRxiv (Cold Spring Harbor Laboratory), Nov 30, 2021
Many range-restricted taxa are currently experiencing population declines yet lack fundamental in... more Many range-restricted taxa are currently experiencing population declines yet lack fundamental information regarding distribution and population size. Establishing baseline estimates for both these key biological parameters is however critical for directing conservation planning for at-risk range-restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). However, calculating all three metrics using standard IUCN approaches relies on a. CC-BY-NC-ND 4.
Many range‐restricted taxa are experiencing population declines, yet we lack fundamental informat... more Many range‐restricted taxa are experiencing population declines, yet we lack fundamental information regarding their distribution and population size. Establishing baseline estimates for both of these key biological parameters is however critical for directing conservation planning for at‐risk range‐restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). 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. 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 Critica...
Quantifying home range size and habitat resource selection are important elements in wildlife eco... more Quantifying home range size and habitat resource selection are important elements in wildlife ecology and are useful for informing conservation action. Many home range estimators and 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. 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. From all home range estimators, the median 95 % home range size was between 39-68 km2 (range: 22-161 km2), with the 50 % core range size between 6-13 km2 (range: 5-33 km2). The space-time autocorrelated kernel density estimate (AKDE) had the largest median 95 % home ra...
From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindana... more From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindanao. Initial results presented here are part of a long-term project that would measure home range size and habitat use of Philippine Eagles, the survival rates of juveniles as well as their dispersal patterns. Out of 3 young birds, only one yielded good telemetric data. The rest of the young birds died within 2 months of tagging. Data on the single bird with good movement data indicate an increase in activity area with increasing age. Overall, juvenile mortality appears high. Among the radio-tagged adults, only a single male bird yielded good telemetric data. Descriptions of nest site use, activity and movement patterns were based on this single male eagle. Whereas forest loss and fragmentation is the ultimate threat to wild populations, hunting and trapping appears to be one proximate reason for recent declines.
The Philippine Eagle, Pithecophaga jefferyi, is a critically endangered bird of prey that is ende... more The Philippine Eagle, Pithecophaga jefferyi, is a critically endangered bird of prey that is endemic to the dipterocarp forests of the Philippines. In this study, data from next-generation sequencing (NGS) were used for the development of microsatellites for the Philippine Eagle. A total of 49,965 microsatellite loci were predicted and 20,960 primer pairs were designed. Forty (40) of these pairs were synthesized and were tested on 20 captive individuals. Twenty (20) of these markers showed high amplification success rates and exhibited polymorphism. A maximum of 24 alleles was detected across the 20 markers with an average of 13.9 alleles, which is remarkably higher than other microsatellite studies in eagles. The resulting values for observed heterozygosity (H o) ranged from 0 to 1.00 with an average of 0.290, while expected heterozygosities ranged from 0.791 to 0.968 with an average of 0.910.
Many range-restricted taxa are currently experiencing severe population declines yet lack fundame... more Many range-restricted taxa are currently experiencing severe population declines yet lack fundamental biological information regarding distribution and population size. Establishing baseline estimates for both these key biological parameters is however critical for directing long-term monitoring and conservation planning for at-risk range-restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three spatial range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). 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. Here, we apply model-based interpolation using an ensemble Species Distribution Model (SDM), correlating occurrences with remote-sensing derived environmental covariates, to calculate IUCN range m...
Two pieces of information are minimally required to conserve endangered raptor species — (i) an e... more Two pieces of information are minimally required to conserve endangered raptor species — (i) an estimate of its remaining global population, and (ii) the main factors responsible for its decline. Data suggest that no more than 400 adult pairs of the Critically Endangered Philippine Eagle could remain in the wild. As to what is causing population decline, shooting and hunting continue to be the primary factor while forest habitat loss is another. This paper reflects on the growing incident of human-caused deaths in Philippine Eagles, prominently on Mindanao Island where estimates suggest more than half of the eagle’s wild population exists. By analyzing data from eagle rescues, surveys, and field monitoring through radio and satellite tracking techniques, this paper shows that shooting and trapping is a “clear and present” danger which may potentially drive the population to extinction even when suitable forest habitats still exist. Cases of death within the last decade show that the...
DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its... more DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its closest relative based on a 650-bp fragment of the cytochrome c oxidase subunit I (COI). In this study, DNA barcodes of members of the family Accipitridae, including Haliastur indus (brahminy kite), Haliaeetus leucogaster (white-bellied sea eagle), Ichthyophaga ichthyaetus (grey-headed fish eagle), Spilornis holospilus (crested serpent-eagle), Spizaetus philippensis (Philippine hawkeagle), and Pithecophaga jefferyi (Philippine eagle), are reported for the first time. All individuals sampled are kept at the Philippine Eagle Center in Davao City, Philippines. Basic local alignment search tool results demonstrated that the COI sequences for these species were unique. The COI gene trees constructed using the maximum-likelihood and neighbourjoining (NJ) methods supported the monophyly of the booted eagles of the Aquilinae and the sea eagles of the Haliaeetinae but not the kites of the Milvinae.
DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its... more DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its closest relative based on a 650-bp fragment of the cytochrome c oxidase subunit I (COI). In this study, DNA barcodes of members of the family Accipitridae, including Haliastur indus (brahminy kite), Haliaeetus leucogaster (white-bellied sea eagle), Ichthyophaga ichthyaetus (grey-headed fish eagle), Spilornis holospilus (crested serpent-eagle), Spizaetus philippensis (Philippine hawkeagle), and Pithecophaga jefferyi (Philippine eagle), are reported for the first time. All individuals sampled are kept at the Philippine Eagle Center in Davao City, Philippines. Basic local alignment search tool results demonstrated that the COI sequences for these species were unique. The COI gene trees constructed using the maximum-likelihood and neighbourjoining (NJ) methods supported the monophyly of the booted eagles of the Aquilinae and the sea eagles of the Haliaeetinae but not the kites of the Milvinae.
The Philippine Eagle Pithecophaga jefferyi , first discovered in 1896, is one of the world's most... more The Philippine Eagle Pithecophaga jefferyi , first discovered in 1896, is one of the world's most endangered eagles. It has been reported primarily from only four main islands of the Philippine archipelago. We have studied it extensively for the past three decades. Using data from 1991 to 1998 as best representing the current status of the species on the island of Mindanao, we estimated the mean nearest-neighbour distances between breeding pairs, with remarkably little variation, to be 12.74 km ( n = 13 nests plus six pairs without located nests, se = ± 0.86 km, range = 8.3-17.5 km). Forest cover within circular plots based on nearest-neighbour pairs, in conjunction with estimates of remaining suitable forest habitat (approximately 14 000 km 2 ), yield estimates of the maximum number of breeding pairs on Mindanao ranging from 82 to 233, depending on how the forest cover is factored into the estimates.
From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindana... more From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindanao. Initial results presented here are part of a long-term project that would measure home range size and habitat use of Philippine Eagles, the survival rates of juveniles as well as their dispersal patterns. Out of 3 young birds, only one yielded good telemetric data. The rest of the young birds died within 2 months of tagging. Data on the single bird with good movement data indicate an increase in activity area with increasing age. Overall, juvenile mortality appears high. Among the radio-tagged adults, only a single male bird yielded good telemetric data. Descriptions of nest site use, activity and movement patterns were based on this single male eagle. Whereas forest loss and fragmentation is the ultimate threat to wild populations, hunting and trapping appears to be one proximate reason for recent declines.
Quantifying home range size and habitat resource selection are important elements in wildlife eco... more Quantifying home range size and habitat resource selection are important elements in wildlife ecology and are useful for informing conservation action. Many home range estimators and 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. 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),. CC-BY-NC-ND 4.
bioRxiv (Cold Spring Harbor Laboratory), Nov 30, 2021
Many range-restricted taxa are currently experiencing population declines yet lack fundamental in... more Many range-restricted taxa are currently experiencing population declines yet lack fundamental information regarding distribution and population size. Establishing baseline estimates for both these key biological parameters is however critical for directing conservation planning for at-risk range-restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). However, calculating all three metrics using standard IUCN approaches relies on a. CC-BY-NC-ND 4.
Many range‐restricted taxa are experiencing population declines, yet we lack fundamental informat... more Many range‐restricted taxa are experiencing population declines, yet we lack fundamental information regarding their distribution and population size. Establishing baseline estimates for both of these key biological parameters is however critical for directing conservation planning for at‐risk range‐restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). 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. 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 Critica...
Quantifying home range size and habitat resource selection are important elements in wildlife eco... more Quantifying home range size and habitat resource selection are important elements in wildlife ecology and are useful for informing conservation action. Many home range estimators and 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. 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. From all home range estimators, the median 95 % home range size was between 39-68 km2 (range: 22-161 km2), with the 50 % core range size between 6-13 km2 (range: 5-33 km2). The space-time autocorrelated kernel density estimate (AKDE) had the largest median 95 % home ra...
From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindana... more From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindanao. Initial results presented here are part of a long-term project that would measure home range size and habitat use of Philippine Eagles, the survival rates of juveniles as well as their dispersal patterns. Out of 3 young birds, only one yielded good telemetric data. The rest of the young birds died within 2 months of tagging. Data on the single bird with good movement data indicate an increase in activity area with increasing age. Overall, juvenile mortality appears high. Among the radio-tagged adults, only a single male bird yielded good telemetric data. Descriptions of nest site use, activity and movement patterns were based on this single male eagle. Whereas forest loss and fragmentation is the ultimate threat to wild populations, hunting and trapping appears to be one proximate reason for recent declines.
The Philippine Eagle, Pithecophaga jefferyi, is a critically endangered bird of prey that is ende... more The Philippine Eagle, Pithecophaga jefferyi, is a critically endangered bird of prey that is endemic to the dipterocarp forests of the Philippines. In this study, data from next-generation sequencing (NGS) were used for the development of microsatellites for the Philippine Eagle. A total of 49,965 microsatellite loci were predicted and 20,960 primer pairs were designed. Forty (40) of these pairs were synthesized and were tested on 20 captive individuals. Twenty (20) of these markers showed high amplification success rates and exhibited polymorphism. A maximum of 24 alleles was detected across the 20 markers with an average of 13.9 alleles, which is remarkably higher than other microsatellite studies in eagles. The resulting values for observed heterozygosity (H o) ranged from 0 to 1.00 with an average of 0.290, while expected heterozygosities ranged from 0.791 to 0.968 with an average of 0.910.
Many range-restricted taxa are currently experiencing severe population declines yet lack fundame... more Many range-restricted taxa are currently experiencing severe population declines yet lack fundamental biological information regarding distribution and population size. Establishing baseline estimates for both these key biological parameters is however critical for directing long-term monitoring and conservation planning for at-risk range-restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three spatial range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). 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. Here, we apply model-based interpolation using an ensemble Species Distribution Model (SDM), correlating occurrences with remote-sensing derived environmental covariates, to calculate IUCN range m...
Two pieces of information are minimally required to conserve endangered raptor species — (i) an e... more Two pieces of information are minimally required to conserve endangered raptor species — (i) an estimate of its remaining global population, and (ii) the main factors responsible for its decline. Data suggest that no more than 400 adult pairs of the Critically Endangered Philippine Eagle could remain in the wild. As to what is causing population decline, shooting and hunting continue to be the primary factor while forest habitat loss is another. This paper reflects on the growing incident of human-caused deaths in Philippine Eagles, prominently on Mindanao Island where estimates suggest more than half of the eagle’s wild population exists. By analyzing data from eagle rescues, surveys, and field monitoring through radio and satellite tracking techniques, this paper shows that shooting and trapping is a “clear and present” danger which may potentially drive the population to extinction even when suitable forest habitats still exist. Cases of death within the last decade show that the...
DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its... more DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its closest relative based on a 650-bp fragment of the cytochrome c oxidase subunit I (COI). In this study, DNA barcodes of members of the family Accipitridae, including Haliastur indus (brahminy kite), Haliaeetus leucogaster (white-bellied sea eagle), Ichthyophaga ichthyaetus (grey-headed fish eagle), Spilornis holospilus (crested serpent-eagle), Spizaetus philippensis (Philippine hawkeagle), and Pithecophaga jefferyi (Philippine eagle), are reported for the first time. All individuals sampled are kept at the Philippine Eagle Center in Davao City, Philippines. Basic local alignment search tool results demonstrated that the COI sequences for these species were unique. The COI gene trees constructed using the maximum-likelihood and neighbourjoining (NJ) methods supported the monophyly of the booted eagles of the Aquilinae and the sea eagles of the Haliaeetinae but not the kites of the Milvinae.
DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its... more DNA barcoding is a molecular method that rapidly identifies an individual to a known taxon or its closest relative based on a 650-bp fragment of the cytochrome c oxidase subunit I (COI). In this study, DNA barcodes of members of the family Accipitridae, including Haliastur indus (brahminy kite), Haliaeetus leucogaster (white-bellied sea eagle), Ichthyophaga ichthyaetus (grey-headed fish eagle), Spilornis holospilus (crested serpent-eagle), Spizaetus philippensis (Philippine hawkeagle), and Pithecophaga jefferyi (Philippine eagle), are reported for the first time. All individuals sampled are kept at the Philippine Eagle Center in Davao City, Philippines. Basic local alignment search tool results demonstrated that the COI sequences for these species were unique. The COI gene trees constructed using the maximum-likelihood and neighbourjoining (NJ) methods supported the monophyly of the booted eagles of the Aquilinae and the sea eagles of the Haliaeetinae but not the kites of the Milvinae.
The Philippine Eagle Pithecophaga jefferyi , first discovered in 1896, is one of the world's most... more The Philippine Eagle Pithecophaga jefferyi , first discovered in 1896, is one of the world's most endangered eagles. It has been reported primarily from only four main islands of the Philippine archipelago. We have studied it extensively for the past three decades. Using data from 1991 to 1998 as best representing the current status of the species on the island of Mindanao, we estimated the mean nearest-neighbour distances between breeding pairs, with remarkably little variation, to be 12.74 km ( n = 13 nests plus six pairs without located nests, se = ± 0.86 km, range = 8.3-17.5 km). Forest cover within circular plots based on nearest-neighbour pairs, in conjunction with estimates of remaining suitable forest habitat (approximately 14 000 km 2 ), yield estimates of the maximum number of breeding pairs on Mindanao ranging from 82 to 233, depending on how the forest cover is factored into the estimates.
From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindana... more From 1998-2001, six Philippine Eagles Pithecophaga jefferyi, were radio-tagged in Central Mindanao. Initial results presented here are part of a long-term project that would measure home range size and habitat use of Philippine Eagles, the survival rates of juveniles as well as their dispersal patterns. Out of 3 young birds, only one yielded good telemetric data. The rest of the young birds died within 2 months of tagging. Data on the single bird with good movement data indicate an increase in activity area with increasing age. Overall, juvenile mortality appears high. Among the radio-tagged adults, only a single male bird yielded good telemetric data. Descriptions of nest site use, activity and movement patterns were based on this single male eagle. Whereas forest loss and fragmentation is the ultimate threat to wild populations, hunting and trapping appears to be one proximate reason for recent declines.
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