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Introduced rats are notorious predators of birds and their nests worldwide, but especially on remote islands. Rats (Rattus exulans) first arrived in Hawai‘i with Polynesian colonists about 1,000 years ago, resulting in deleterious consequences for native birds and ecosystems. Since Western contact in 1778, two additional rat species have become established in Hawai‘i, including the highly invasive black rat (R. rattus), which arrived in the late 1800s. Black rats have contributed substantially to the historical loss of native forest bird populations, in part through nest depredation. The USGS evaluated rat control as a management tool to improve the breeding success of native birds and to facilitate native plant regeneration to recover native ecosystems.
Overview:
A high priority of natural resource managers is research to evaluate how management of alien predators can aid the recovery and increase the resiliency and stability of mesic montane forests of Hawai'i Volcanoes National Park (HAVO). These forests have been listed as globally imperiled by the International Union for Conservation of Nature and contain biologically rich sites that support many rare, declining, and threatened or endangered species. Ecosystem restoration at HAVO began in the 1970s with the pioneering removal and exclusion of feral ungulates, which resulted in or is leading toward recovery of the native tree canopy across broad and diverse swaths of mesic montane forest. More recently, a program to stabilize rare plants has led to the reintroduction or augmentation of more than 22 native taxa, including 10 federally listed species. Additionally, select invasive weed species are being controlled, yet the recovery of native understory vegetation and invertebrate and vertebrate communities has been limited. The USGS investigated whether predators such as black rats are impeding bird restoration in these recovering forests.
Hawai‘i ‘elepaio (Chasiempis sandwichensis) are insectivorous forest birds and are common in native montane forest habitat within HAVO. Their nests are relatively accessible for monitoring and are known to be vulnerable to rat depredation. ‘Elepaio nesting success, nest depredation, and rat abundance were monitored during 2015–2017 within study plots in HAVO. Monitoring was conducted before and after rodenticide treatment and compared between paired treatment and non-treatment plots.
Highlights and Key Findings:
USGS researchers gained new insights into how to prioritize rat control efforts given the challenges of reducing or eliminating their populations. In some areas, bird populations were declining despite forest recovery from invasive ungulate (goats, pigs, cattle) removal. Researchers quantified the impact of rat depredation on common forest bird species, including the increased nesting response of Hawai‘i ‘elepaio after the removal of black rats.
In related studies of black rat removal and the native tree hau kuahiwi (Hibiscadelphus giffardianus), USGS researchers found an improvement in the ability of the tree to retain fruit.
Field studies and data collection were completed in 2017. Data analysis and manuscript preparation continued through 2018 and 2019. See Publications and Data tabs for more information.
See the Multimedia tab for video footage of rat predation of bird nests.
Below are multimedia items associated with this project.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Introduced rats are notorious predators of birds and their nests worldwide, but especially on remote islands. Rats (Rattus exulans) first arrived in Hawai‘i with Polynesian colonists about 1,000 years ago, resulting in deleterious consequences for native birds and ecosystems. Since Western contact in 1778, two additional rat species have become established in Hawai‘i, including the highly invasive black rat (R. rattus), which arrived in the late 1800s. Black rats have contributed substantially to the historical loss of native forest bird populations, in part through nest depredation. The USGS evaluated rat control as a management tool to improve the breeding success of native birds and to facilitate native plant regeneration to recover native ecosystems.
Overview:
A high priority of natural resource managers is research to evaluate how management of alien predators can aid the recovery and increase the resiliency and stability of mesic montane forests of Hawai'i Volcanoes National Park (HAVO). These forests have been listed as globally imperiled by the International Union for Conservation of Nature and contain biologically rich sites that support many rare, declining, and threatened or endangered species. Ecosystem restoration at HAVO began in the 1970s with the pioneering removal and exclusion of feral ungulates, which resulted in or is leading toward recovery of the native tree canopy across broad and diverse swaths of mesic montane forest. More recently, a program to stabilize rare plants has led to the reintroduction or augmentation of more than 22 native taxa, including 10 federally listed species. Additionally, select invasive weed species are being controlled, yet the recovery of native understory vegetation and invertebrate and vertebrate communities has been limited. The USGS investigated whether predators such as black rats are impeding bird restoration in these recovering forests.
Hawai‘i ‘elepaio (Chasiempis sandwichensis) are insectivorous forest birds and are common in native montane forest habitat within HAVO. Their nests are relatively accessible for monitoring and are known to be vulnerable to rat depredation. ‘Elepaio nesting success, nest depredation, and rat abundance were monitored during 2015–2017 within study plots in HAVO. Monitoring was conducted before and after rodenticide treatment and compared between paired treatment and non-treatment plots.
Highlights and Key Findings:
USGS researchers gained new insights into how to prioritize rat control efforts given the challenges of reducing or eliminating their populations. In some areas, bird populations were declining despite forest recovery from invasive ungulate (goats, pigs, cattle) removal. Researchers quantified the impact of rat depredation on common forest bird species, including the increased nesting response of Hawai‘i ‘elepaio after the removal of black rats.
In related studies of black rat removal and the native tree hau kuahiwi (Hibiscadelphus giffardianus), USGS researchers found an improvement in the ability of the tree to retain fruit.
Field studies and data collection were completed in 2017. Data analysis and manuscript preparation continued through 2018 and 2019. See Publications and Data tabs for more information.
See the Multimedia tab for video footage of rat predation of bird nests.
Below are multimedia items associated with this project.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.
Black rats were unintentionally introduced to Hawai’i in the late 1800s, most likely as hitchhikers on trading vessels. Since their introduction, they have disrupted native ecosystems by destroying native plants, eating native arthropods, and depredating bird nests.