Geology topics

Steven C. Hess

Publications and source records attributed to Steven C. Hess.

At least 19 recordsLinked to original sources

USGS2025

Vertebrates in trade that pose high invasion risk to the United States

The United States imports thousands of live vertebrate species annually as part of legal trade. Escapes and releases from captivity are major pathways of invasion, however, the risk posed by the thousands of imported vertebrate species has not been systematically assessed. We conducted a horizon scan that used a data-driven climate match to filter a list of nearly 15,000 taxa drawn from across the globe of imported fish, amphibians, reptiles, birds, and mammals for rapid assessment by taxonomic experts. Experts evaluated 840 species and identified 32 (22 reptiles and 10 fishes) as having the highest risk for establishment, spread, and negative impacts. Of those high-risk species, the majority have the capacity to disrupt ecosystem processes via their role as top predators or the unique ecological niches that they occupy, while several of the snake species pose a threat to human health. High-risk species were often scored with high confidence while in contrast, low scores were attributed to a combination of ecological redundancy, low propagule pressure, or low climate match while low confidence arose from a lack of information in the literature (i.e., data deficiency). Our study therefore highlights legally imported species likely to cause the greatest harm with the recognition that many other species could also become invasive in the United States. The ranked list of vertebrate threats can be used to prioritize watchlists and inform the development of targeted regulations for importation can be applied to regions to provide a rapid, preliminary screening for large pools of potential invaders.

Biological Conservation↗

USGS2024

Using systematic conservation planning to recover climate resilient habitat for threatened and endangered species while retaining areas of cultural importance

The effective management of at-risk species often requires fine-scale actions by natural resource managers. However, balancing these actions with concurrent land uses is challenging, particularly when compounded by the interplay of climate shifts, and escalating wildland–urban interface conflicts. We used spatial prioritization tools designed for biodiversity conservation to help resource managers on the Island of Lānaʻi prioritize mutually exclusive land use objectives: endangered species recovery and subsistence and recreational hunting. We weighed the current and anticipated future distributions of threatened and endangered plant species against the distribution of non-native game mammals to plan for species recovery more effectively. Prioritization results identified multiple footprints that could support recovery of all endangered species targets in climate resilient areas while retaining the majority of existing hunting areas. However, very little native vegetation was retained in conservation footprints without deliberate inclusion, which increased footprint area by 268%. Scenarios which prioritized contiguous conservation areas also dramatically increased conservation footprint area, although these scenarios may reduce associated fencing costs. This work demonstrates how spatial prioritization may guide localized species recovery efforts by supporting long-term conservation planning that addresses anticipated climate-driven increases in conflict between conservation and other land uses, with clear applicability beyond Lānaʻi.

Conservation↗

USGS2023

Ecological associations of non-native ungulates on the Hawaiian Island of Lāna‘i

Sustained-yield hunting of introduced ungulates in the Hawaiian Islands often conflicts with the conservation of native species, but there is little reliable data to guide effective management. European mouflon sheep ( Ovis musimon ; mouflon) and axis deer ( Axis axis ; deer) were introduced on the island of Lāna‘i to provide additional hunting opportunities. Managers will require better information regarding the ecological associations of introduced ungulate species, relative to the habitats occupied, to resolve longstanding conflicts between native species conservation and sustained-yield hunting on islands. To address this information need, we modeled sheep and deer ecological associations, habitat-use, and suitability using data obtained from an intensive aerial survey completed in 2013 and temporally matching environmental data. In habitat suitability models evaluated by Receiver Operating Characteristic (ROC) metrics, predictor importance in a generalized linear model (GLM) of deer decreased in the following order: afternoon cloud cover, topographic slope, mean annual precipitation (MAP), elevation, normalized difference vegetation index (NDVI), and bare soil index. In a random GLM model of mouflon, predictor importance decreased in the following order: afternoon cloud cover, deer habitat suitability, NDVI, bare soil index, topographic slope, elevation, and MAP. Mouflon were restricted to lower elevation arid slopes, whereas deer were more broadly distributed throughout upland environments of the island. The presence of deer was also an important predictor for mouflon distribution, although mouflon was not an important predictor of deer, suggesting asymmetrical competition. Removal of the more abundant deer population may lead to an increase in abundance and distribution of mouflon without containment. This work represents the first habitat suitability analysis for all nonnative ungulates on any entire Hawaiian island. Our results are applicable to other islands where conflicts may arise with introduced ungulates, sustained-yield hunting, and native species conservation.

Hawaii↗

USGS2021

Efficacy of detection canines for avian botulism surveillance and mitigation

Hawai'i's endangered waterbirds have experienced epizootics caused by ingestion of prey that accumulated a botulinum neurotoxin produced by the anaerobic bacterium Clostridium botulinum (avian botulism; Type C). Waterbird carcasses, necrophagous flies, and their larvae initiate and spread avian botulism, a food-borne paralytic disease lethal to waterbirds. Each new carcass has potential to develop toxin-accumulating necrophagous vectors amplifying outbreaks and killing hundreds of endangered waterbirds. Early carcass removal is an effective mitigation strategy for preventing avian intoxication, toxin concentration in necrophagous and secondary food webs, and reducing the magnitude of epizootics. However, rapid detection of carcasses can be problematic and labor intensive. Therefore, we tested a new method using scent detection canines for avian botulism surveillance on Kaua'i Island. During operational surveillance and a randomized double-blind field trial, trained detector canines with experienced field handlers improved carcass detection probability, especially in dense vegetation. Detector canines could be combined with conventional surveillance to optimize search strategies for carcass removal and are a useful tool to reduce risks of the initiation and propagation of avian botulism.

Hawaii↗

USGS2018

Evaluating the long-term management of introduced ungulates to protect the palila, an endangered bird, and its criticial habitat in subalpine forest of Mauna Kea, Hawai'i

Under the multiple-use paradigm, conflicts may arise when protection of an endangered species must compete with other management objectives. To resolve such a conflict in the Critical Habitat of the endangered Hawaiian honeycreeper, palila (Loxioides bailleui), federal courts ordered the eradication of introduced ungulates responsible for damaging the māmane (Sophora chrysophylla) forest on which palila depend. During 1980–2011, a total of 18,130 sheep (Ovis aries and O. gmelini musimon) and 310 goats (Capra hircus) were removed from Palila Critical Habitat (PCH) primarily by public hunters (54%) and secondarily by aerial shooting. Nevertheless, our analysis indicates that ungulates have increased over time. Palila numbers have declined sharply since 2003 due to long-term habitat degradation by ungulates and drought. Although culling ungulate populations has allowed some habitat improvement, their complete removal is necessary for palila to recover, especially given the potential for continued drought. Introduced predators are being controlled to reduce palila mortality, māmane and other native trees are being planted to restore some areas, and fencing is being constructed to prevent ungulate immigration. Funds are recently available for more effective eradication efforts, which are urgently needed to eliminate browsing damage in PCH and protect the palila from extinction.

Hawaii↗

USGS2018

Biology and impacts of Pacific Islands invasive species. 14. Sus scrofa the feral pig (Artiodactyla: Suidae)

Feral pigs ( Sus scrofa L.) are perhaps the most abundant, widespread, and economically significant large introduced vertebrate across the Pacific island region. Unlike many other nonnative invasive species, feral pigs have both cultural and recreational importance in the region, complicating their management. Today, Pacific island feral pigs are a mixture of several strains of domestic swine, Asiatic wild boar, and European wild boar. Due to their generalist diet and rooting behavior, feral pigs alter soils and watersheds and negatively impact native and nonnative flora and fauna. As a result, feral pigs have played a role in the extinction of several species of plants and animals on Pacific islands and have negative effects on both ecotourism and agricultural industries in the region. Despite numerous published studies on feral pigs in the Pacific island region, of which the majority include systematic analyses of original empirical data, some fundamental aspects of feral pig ecology remain poorly characterized, at least partly due to the remote and inaccessible environments that they often inhabit. To address these knowledge gaps, effort should be made to integrate research conducted outside the Pacific island region into local management strategies. This review summarizes the origins, history, ecology, environmental effects, and current management of feral pigs in the Pacific island region; integrates regional scientific findings with those of other insular and continental systems; and identifies current knowledge gaps requiring further research to inform the ecology and management of this impactful invasive species.

Hawai'i↗

USGS2017

Monitoring eradication of European mouflon sheep from the Kahuku Unit of Hawai‘i Volcanoes National Park

European mouflon ( Ovis gmelini musimon ), the world's smallest wild sheep, have proliferated and degraded fragile native ecosystems in the Hawaiian Islands through browsing, bark stripping, and trampling, including native forests within Hawai‘i Volcanoes National Park (HAVO). HAVO resource managers initiated ungulate control efforts in the 469 km 2 Kahuku Unit after it was acquired in 2003. We tracked control effort and used aerial surveys in a 64.7 km 2 area from 2004 to 2017 and more intensive ground surveys and camera-trap monitoring to detect the last remaining animals within a 25.9 km 2 subunit after it was enclosed by fence in 2012. Aerial shooting yielded the most removals per unit effort (3.2 animals/ hour), resulting in 261 animals. However, ground-based methods yielded 4,607 removals overall, 3,038 of which resulted from assistance of volunteers. Ground shooting with dogs, intensive aerial shooting, ground sweeps, and forward-looking infrared (FLIR)-assisted shooting were necessary to find and remove the last remaining mouflon. The Judas technique, baiting, and trapping were not successful in attracting or detecting small numbers of remaining individuals. Effort expended to remove each mouflon increased nearly 15-fold during the last 3 yr of eradication effort from 2013 to 2016. Complementary active and passive monitoring techniques allowed us to track the effectiveness of control effort and reveal locations of small groups to staff. The effort and variety of methods required to eradicate mouflon from an enclosed unit of moderate size illustrates the difficulty of scaling up to entire populations of wild ungulates from unenclosed areas.

Hawai'i↗

USGS2016

Conversion of native terrestrial ecosystems in Hawai‘i to novel grazing systems: a review

The remote oceanic islands of Hawai‘i exemplify the transformative effects that non-native herbivorous mammals can bring to isolated terrestrial ecosystems. We reviewed published literature containing systematically collected, analyzed, and peer-reviewed original data specifically addressing direct effects of non-native hoofed mammals (ungulates) on terrestrial ecosystems, and indirect effects and interactions on ecosystem processes in Hawai‘i. The effects of ungulates on native vegetation and ecosystems were addressed in 58 original studies and mostly showed strong short-term regeneration of dominant native trees and understory ferns after ungulate removal, but unassisted recovery was dependent on the extent of previous degradation. Ungulates were associated with herbivory, bark-stripping, disturbance by hoof action, soil erosion, enhanced nutrient cycling from the interaction of herbivory and grasses, and increased pyrogenicity and competition between native plants and pasture grasses. No studies demonstrated that ungulates benefitted native ecosystems except in short-term fire-risk reduction. However, non-native plants became problematic and continued to proliferate after release from herbivory, including at least 11 species of non-native pasture grasses that had become established prior to ungulate removal. Competition from non-native grasses inhibited native species regeneration where degradation was extensive. These processes have created novel grazing systems which, in some cases, have irreversibly altered Hawaii’s terrestrial ecology. Non-native plant control and outplanting of rarer native species will be necessary for recovery where degradation has been extensive. Lack of unassisted recovery in some locations should not be construed as a reason to not attempt restoration of other ecosystems.

Biological Invasions↗

USGS2016

Changes in habitat use and distribution of mouflon in the Kahuku Unit of Hawai‘i Volcanoes National Park

European mouflon sheep ( Ovis gmelini musimon ) were introduced to Kahuku Ranch on Hawai‘i Island in 1968 and 1974 for trophy hunting and have been detrimental to the native ecosystem by trampling, bark stripping, and browsing vegetation. In 2003, Hawai‘i Volcanoes National Park acquired Kahuku Ranch and managers began removing mouflon. The objective of this project was to determine whether hunting has changed the distribution of mouflon in Kahuku, to better understand mouflon behaviour and to expedite eradication efforts. Locations from hunting and GPS telemetry data during 2007–14 were used to determine the effect of hunting on mouflon distribution by examining distance to roads and habitat use. Mouflon seemed to avoid roads after hunting pressure increased and their distribution within vegetation types changed over time. Mouflon without hunting pressure were detected in native shrub habitat in 68% of all observations. Hunted mouflon were encountered less in native shrub habitat and more in other habitats including open forest, closed forest, and areas with no vegetation. These changes suggest that hunting has influenced the distribution of mouflon over time away from native shrub and into other vegetation types where they may be more difficult to control.

Hawai‘i↗

USGS2016

Federal collaboration in science for invasive mammal management in U.S. National Parks and Wildlife Refuges of the Pacific Islands

Some of the most isolated islands in the Pacific Ocean are home to US National Parks and Wildlife Refuges. These islands are known for flora and fauna that occur nowhere else, but also for invasive species and other factors which have resulted in the disproportionate extinction of native species. The control of invasive mammals is the single most expensive natural resource management activity essential for restoring ecological integrity to parks in the Hawaiian Islands, American Samoa, and the islands of Guam and Saipan. Science-based applications supporting management efforts have been shaped by longstanding collaborative federal research programs over the past four decades. Consequently, feral goats (Capra hircus) have been removed from >690 km2 in National Parks, and feral pigs (Sus scrofa) have been removed from >367 km2 of federal lands of Hawai‘i, bringing about the gradual recovery of forest ecosystems. The exclusion of other non-native ungulates and invasive mammals is now being undertaken with more sophisticated control techniques and fences. New fence designs are now capable of excluding feral cats (Felis catus) from large areas to protect endangered native waterfowl and nesting seabirds. Rodenticides which have been tested and registered for hand and aerial broadcast in Hawai‘i have been used to eradicate rats from small offshore islands to protect nesting seabirds and are now being applied to montane environments of larger islands to protect forest birds. Forward-looking infrared radar (FLIR) is also being applied to locate wild ungulates which were more recently introduced to some islands. All invasive mammals have been eradicated from some remote small islands, and it may soon be possible to manage areas on larger islands to be free of invasive mammals at least during seasonally important periods for native species.

Conference Paper↗

USGS2015

Book review: Restoring paradise: Rethinking and rebuilding nature in Hawaii

The native ecosystems of Hawai‘i have been severely degraded by the introduction of herbivorous mammals and a myriad of invasive plant species. Left unmanaged, most natural areas would continue along a trajectory towards domination by nonnative species; however, several projects have undertaken the daunting task of ecological restoration, four of which are the subject of Restoring Paradise by Robert Cabin: Hakalau Forest National Wildlife Refuge; Hawai‘i Volcanoes National Park; the Auwahi dryland forest, Maui and Limahuli Garden and Preserve, Kaua‘i. After an introductory section discussing the setting and factors that have contributed to so much of the degradation and extinction of Hawai‘i’s native biota, Cabin outlines two different views of restoration in two central sections of the book: ad hoc, trial-and-error approaches versus the careful application of science to direct restoration. The time-tested methods of fence construction, ungulate removal, weed control, and replanting native species with the help of numerous volunteers and community support are presented in marked contrast to inconsistent applications of science in guiding restoration, and illustrated by some of the author’s unsuccessful research. The book is largely presented as a non-technical first-person account of travels and meetings with key personalities driving restoration projects. The philosophies of restoration practitioners are embedded in passages from interviews. Setbacks, obstacles, logistical constraints, and successes are narrated in between as Cabin revisits each of the restoration sites. The utility of science in restoration is frequently questioned by the author and sometimes abandoned by practitioners in favour of a ‘let-nature-take-its-course’ approach. Review info: Restoring Paradise: Rethinking and Rebuilding Nature in Hawaii . By Robert J. Cabin, 2013. ISBN: 978-0822836931, 236 pp.

Pacific Conservation Biology↗

USGS2015

Vegetation and non-native ungulate monitoring at the Big Island National Wildlife Refuge Complex 2010–2014.

The Hakalau Forest Unit (HFU) of Big Island National Wildlife Refuge Complex (BINWRC) has intensively managed feral cattle (Bos taurus) and pigs (Sus scrofa) and monitored non-native ungulate presence and distribution during surveys of all managed areas since 1988. We: 1) provide results from recent ungulate surveys at HFU to determine current feral pig abundance and distribution; 2) present results of surveys of ungulate presence and distribution at the Kona Forest Unit (KFU); 3) present results of surveys of weed presence and cover at both refuge units; and 4) present baseline results from long-term vegetation monitoring plots at KFU. Overall pig abundance appears to have decreased at HFU, although not significantly, over the period from 2010 to 2014. Management units 2 and 4 contained the majority of pigs at HFU. Pig density outside of adjacent managed areas has declined significantly from 2010 to 2014 for unknown reasons. Ungulate sign occurred in > 50% of plots at KFU during the November 2012 and September 2013 surveys, but ungulate sign occurred in < 28% of plots during three other surveys. The ability to differentiate sign of ungulate species remains problematic at KFU. Changes in weed cover do not yet demonstrate any strong temporal pattern. Spatial patterns are more pronounced; however, some weed species may not be reliably represented due to observers’ abilities to recognize less common weeds. Nonetheless, the distribution and cover of fireweed (Senecio madagascariensis) at KFU may have increased over the study period. Vegetation surveys documented baseline floristic composition and forest structure at KFU. It is not known if this current amount of emerging cover is sufficient for long-term self-sustaining forest canopy regeneration; however, numerous ‘ōhi‘a seedlings were found in the wet forest and mesic ‘ōhi‘a habitats, indicating an ample viable seed source and robust potential for forest regeneration.

Hawaii↗

USGS2015

Anatomy of an eradication effort: Removing Hawaii's illegally introduced axis deer

In February 2011, a rancher in the rural southern part of Hawaii Island reported a large mammal on her land. Her call mobilized several agencies led by the Big Island Invasive Species Committee (BIISC), a partnership to prevent, detect, and control the establishment and spread of invasive species, to sit up and take notice. Agency biologists installed camera traps to identify the animal, and a few months later verified the diagnostic field marks of a chervid with spots. The animal in questions was a chital , or axis deer ( Axis axis )--a species native to tropical and subtropical India. Although the deer are abundant on the islands of Molokai, Lānai, and Maui, officials knew they weren't capable of swimming across the notoriously treacherous ʻAlenuihāhā channel, and subsequently suspected human intervention. Soon after the rancher's report, the U.S. Fish and Wildlife Service launched an investigation, which revealed that in December 2009, a helicopter pilot and rancher from Maui had covertly transported four deer in exchange for about a dozen European mouflon sheep ( Ovis gmelini musimon ) (Tummons 2011a, b)--a species also valued for trophies and meat. Because neither species was established in the wild on either of the islands, in June 2012, state lawmakers responded by specifically banning "the international possession or interisland transportation or release of wild or feral deer" (Honolulu Star-Advertiser 2012). The two individuals were prosecuted under the Lacey Act for transporting wildlife between islands with the intent to guide hunting for out-of-state residents (Stephens Media 2012), while the individual who provided the mouflon was sentenced to community service. Further, the helicopter pilot agreed to provide 500 hours of flight time to locate and eradicate the Hawaii Island deer population in restitution.

Hawai'i↗

USGS2014

How much land is needed for feral pig hunting in Hawai'i?

Hunting is often considered to be incompatible with conservation of native biota and watershed functions in Hawai'i. Management actions for conservation generally exclude large non-native mammals from natural areas, thereby reducing the amount of land area available for hunting activities and the maintenance of sustainable game populations. An approach which may be useful in addressing the necessary minimum amount of land area allocated for hunting in Hawai'i is to determine the amount of land area necessary for sustaining populations of hunted animals to meet current levels harvested by the public. We ask: What is the total amount of land necessary to provide sustained-yield hunting of game meat for food at the current harvest level on Hawai'i Island if only feral pigs (Sus scrofa) were to be harvested? We used a simplistic analysis to estimate that 1 317.6 km2-1 651.4 km2 would be necessary to produce 187 333.6 kg of feral pig meat annually based on the range of dressed weight per whole pig, the proportion of a pig population that can be sustainably removed annually, and the density of pig populations in the wild. This amount of area comprises 12.6-15.8% of the total land area of Hawai'i Island, but more likely represents 27.6-43.5% of areas that may be compatible with sustained-yield hunting.

Hawai'i↗

USGS2014

Habitat and food preferences of the endangered Palila (Loxioides bailleui) on Mauna Kea, Hawai'i

Seeds and flowers of the leguminous māmane ( Sophora chrysophylla ) tree are the primary food resource of the federally endangered Palila ( Loxioides bailleui ; Fringillidae: Drepanidinae), which is now restricted to dry subalpine woodland on Mauna Kea Volcano on the island of Hawai'i because of centuries of habitat degradation by non-native ungulates. Palila are morphologically and behaviorally adapted to consume mÄmane seeds by grasping seed pods with their feet and opening pods with stout bills and demonstrate limited ability to exploit alternative food resources. This degree of single species dependency is rare among birds and illustrates unique adaptations that also occurred in other Hawaiian species that are now extinct. In mixed-woodland with co-dominant naio ( Myoporum sandwicense ), Palila spent 1.7-3.9 times longer in māmane than in naio during foraging observations where naio was 1.3-4.6 times as dense as māmane. Naio fruit was readily available, but it comprised proportionally <11% of food items taken by Palila. Although māmane flowers were more abundant than māmane pods throughout this study except at one lower-elevation mixed-woodland site, Palila spent more time foraging on pods than flowers in both māmane woodland and mixed-woodland, but consumed more flowers than pods in mixed-woodland. Insects, which have been reported as an important component of the diet of Palila, were apparently taken rarely in this study. Protecting and restoring māmane in woodlands adjacent to the current range of Palila will benefit their recovery, allowing them to exploit increased food availability in areas of their former range.

Hawai'i↗

USGS2014

Environmental conditions associated with lesions in introduced free-ranging sheep in Hawai‘i

Wildlife species which have been translocated between temperate and tropical regions of the world provide unique opportunities to understand how disease processes may be affected by environmental conditions. European mouflon sheep (Ovis gmelini musimon) from the Mediterranean Islands were introduced to the Hawaiian Islands for sport hunting beginning in 1954 and were subsequently hybridized with feral domestic sheep (O. aries), which had been introduced in 1793. Three isolated mouflon populations have become established in the Hawaiian Islands but diseases in these populations have been little studied. The objective of this study was to evaluate and compare gross and histologic lesions in respiratory, renal, and hepatic systems of free-ranging sheep in two isolated volcanic environments on Hawai‘i Island. Tissue and fecal samples were collected in conjunction with population reductions during February 2011. We found gross or histologic evidence of lungworm infection in 44/49 sheep from Mauna Loa which were exposed to gaseous emissions from Kīlauea Volcano. In contrast, only 7/50 sheep from Mauna Kea had lesions consistent with lungworm, but Mauna Kea sheep had significantly more upper respiratory tract inflammation and hyperplasia consistent with chronic antigenic stimulation, possibly associated with exposure to fine airborne particulates during extended drought conditions. We hypothesize that gasses from Kīlauea Volcano contributed to severity of respiratory disease principally associated with chronic lungworm infections at Mauna Loa; however, there were numerous other potentially confounding environmental factors and interactions that merit further investigation.

Hawai'i↗

USGS2014

Palila restoration research, 1996−2012

The Palila Restoration Project was initiated in 1996 by the U.S. Geological Survey to assist government agencies mitigate the effects of realigning Saddle Road (Highway 200) through Palila Critical Habitat (U.S. Fish and Wildlife Service 1998, Federal Highway Administration 1999). Ecological research on the palila (Loxioides bailleui), an endangered Hawaiian forest bird, carried out by the U.S. Geological Survey (formerly organized as the Research Division of U.S. Fish and Wildlife Service) since 1987 and research conducted by the Palila Restoration Project provided the scientific bases for developing a recovery strategy (U.S. Fish and Wildlife Service 2006) and its adaptive implementation. The main objectives of the Palila Restoration Project were to develop techniques for reintroducing the palila to a portion of its former range, investigate the biological threats to the palila and its habitat, and synthesize the existing body of ecological knowledge concerning the palila. Five broad study themes formed the research framework: 1. Population reintroduction and restoration 2. Demography and breeding ecology 3. Habitat use and food ecology 4. Vegetation ecology 5. Predator ecology and management An element that was not included in the research program of the project was the ecology and management of introduced ungulates, which has historically constituted the single greatest threat to Palila Critical Habitat (Banko et al. 2009). The absence of ungulate studies should not be interpreted to mean that we believe ungulates no longer damage palila habitat. Other research has already established that removing alien browsers and grazers from Mauna Kea is essential for the recovery of the subalpine forest on which palila now depend (Scowcroft and Giffin 1983; Scowcroft and Sakai 1983; Scowcroft and Conrad 1988, 1992; Hess et al. 1999). Moreover, the Federal District Court of Hawai‘i has ordered the state of Hawai‘i to remove browsing ungulates from Palila Critical Habitat (Banko et al. 2009, Hess and Banko 2011). This final report summarizes results of Palila Restoration Project research from December 1996 to December 2012. Even though some results contained in this report have been published in scientific journals and other technical reports (Appendix I), they are included here to provide a comprehensive chronicle of all project activities.

Hawaii↗

USGS2013

Corridor- and stopover-use of the Hawaiian goose ( Branta sandvicensis ), an intratropical altitudinal migrant

We outfitted six male Hawaiian geese, or nene (Branta sandvicensis), with 45-g solar-powered satellite transmitters and collected four location coordinates d −1 from 2010 to 2012. We used 6193 coordinates to characterize migration corridors, habitat preferences and temporal patterns of displacement for 16 migration events with Brownian bridge utilization distributions (BBUD). We used 1552 coordinates to characterize stopovers from 37 shorter-distance movement events with 25% BBUDs. Two subpopulations used a well-defined common migration corridor spanning a broad gradient of elevation. Use of native-dominated subalpine shrubland was 2.81 times more likely than the availability of this land-cover type. The nene differed from other tropical and temperate-zone migrant birds in that: (1) migration distance and the number of stopovers were unrelated (Mann–Whitney test W = 241, P < 0.006), and; (2) individual movements were not unidirectional suggesting that social interactions may be more important than refuelling en route; but like other species, nene made more direct migrations with fewer stopovers in return to breeding areas (0.58 ± 0.50) than in migration away from breeding areas (1.64 ± 0.48). Our findings, combined with the direction and timing of migration, which is opposite that of most other intratropical migrants, suggest fundamentally different drivers of altitudinal migration.

Journal of Tropical Ecology↗