Movement Patterns of the Endangered Hawaiian Hawk
To document movement patterns and habitat use of Hawiian Hawks, GPS tags were attached to 17 individuals to track their movement across continuous, fragmented, and urban landscapes. We are now gathering multi-year tracking data to assess key aspects of habitat needs, and how these birds navigate through different ecosystems.
Overview:
The endangered Hawaiian hawk or ‘Io is native and restricted to the Island of Hawai‘i. The most recent ‘Io population estimate is 3,000 hawks, based on two surveys from 1998-1999 and 2007. Historically ‘Io habitat was limited to native forests and nearby open areas with high densities of large ‘ōhi`a trees. Broad scale forest loss due to human agriculture contributed to the elimination of ‘Io from all Hawaiian Islands except Hawai‘i, and habitat loss continues today. Of concern, Rapid ‘Ōhi`a Death, an emerging disease caused by fungi, threatens to degrade large areas of occupied habitat. Also, unpredictable events such as the 2018 Kīlauea Volcano eruption can increase habitat loss.
We see ‘Io in many habitat types, but questions remain about how they are using habitat at the landscape level. Are some habitats only infrequently visited? Do fragmented habitats require larger home ranges? Do ‘Io in urban and fragmented areas need nearby native forests for at least some portion of their range? Answers to these questions are important for understanding what habitat is suitable, drivers of different population densities, and the hawk’s ability to adjust to human influenced habitats.
Objectives:
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Home Range Size: Document ‘Io home range size for one year using solar powered GPS tracking devices. Home ranges are the area required for an animal to make their living, and the size of home ranges can be a measure of the density of resources. Higher quality habitats should have higher densities of resources, and thus smaller home ranges.
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Movement Patterns: Animals move across the landscape to maximize fitness. We will analyze movement patterns to identify areas important for roosting, nesting, and foraging. Areas used in higher/lower frequency indicate areas of importance/avoidance, such as attraction to food sources or avoidance of developed areas. We will also evaluate the stability of use within a home range over time to assess seasonal changes in resource availability.
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Habitat Use: Identify important habitats ‘Io use and assess the use frequency in comparison to other available habitats. The habitats ‘Io select more or less than others indicate features of quality habitat and features of avoided habitat. We compare patterns in habitat use between birds in different landscape groups, to evaluate if certain habitat features are constant across the landscape.
To document movement patterns and habitat use of Hawiian Hawks, GPS tags were attached to 17 individuals to track their movement across continuous, fragmented, and urban landscapes. We are now gathering multi-year tracking data to assess key aspects of habitat needs, and how these birds navigate through different ecosystems.
Overview:
The endangered Hawaiian hawk or ‘Io is native and restricted to the Island of Hawai‘i. The most recent ‘Io population estimate is 3,000 hawks, based on two surveys from 1998-1999 and 2007. Historically ‘Io habitat was limited to native forests and nearby open areas with high densities of large ‘ōhi`a trees. Broad scale forest loss due to human agriculture contributed to the elimination of ‘Io from all Hawaiian Islands except Hawai‘i, and habitat loss continues today. Of concern, Rapid ‘Ōhi`a Death, an emerging disease caused by fungi, threatens to degrade large areas of occupied habitat. Also, unpredictable events such as the 2018 Kīlauea Volcano eruption can increase habitat loss.
We see ‘Io in many habitat types, but questions remain about how they are using habitat at the landscape level. Are some habitats only infrequently visited? Do fragmented habitats require larger home ranges? Do ‘Io in urban and fragmented areas need nearby native forests for at least some portion of their range? Answers to these questions are important for understanding what habitat is suitable, drivers of different population densities, and the hawk’s ability to adjust to human influenced habitats.
Objectives:
-
Home Range Size: Document ‘Io home range size for one year using solar powered GPS tracking devices. Home ranges are the area required for an animal to make their living, and the size of home ranges can be a measure of the density of resources. Higher quality habitats should have higher densities of resources, and thus smaller home ranges.
-
Movement Patterns: Animals move across the landscape to maximize fitness. We will analyze movement patterns to identify areas important for roosting, nesting, and foraging. Areas used in higher/lower frequency indicate areas of importance/avoidance, such as attraction to food sources or avoidance of developed areas. We will also evaluate the stability of use within a home range over time to assess seasonal changes in resource availability.
-
Habitat Use: Identify important habitats ‘Io use and assess the use frequency in comparison to other available habitats. The habitats ‘Io select more or less than others indicate features of quality habitat and features of avoided habitat. We compare patterns in habitat use between birds in different landscape groups, to evaluate if certain habitat features are constant across the landscape.