Marcos Gorresen P.,University of Hawaii at Hilo |
Cryan P.M.,Fort Collins Science Center |
Dalton D.C.,Bat Research and Consulting |
Wolf S.,Bat Research and Consulting |
Bonaccorso F.J.,Pacific Island Ecosystems Research Center
Acta Chiropterologica | Year: 2015
Insectivorous bats are well known for their abilities to find and pursue flying insect prey at close range using echolocation, but they also rely heavily on vision. For example, at night bats use vision to orient across landscapes, avoid large obstacles, and locate roosts. Although lacking sharp visual acuity, the eyes of bats evolved to function at very low levels of illumination. Recent evidence based on genetics, immunohistochemistry, and laboratory behavioral trials indicated that many bats can see ultraviolet light (UV), at least at illumination levels similar to or brighter than those before twilight. Despite this growing evidence for potentially widespread UV vision in bats, the prevalence of UV vision among bats remains unknown and has not been studied outside of the laboratory. We used a Y-maze to test whether wild-caught bats could see reflected UV light and whether such UV vision functions at the dim lighting conditions typically experienced by night-flying bats. Seven insectivorous species of bats, representing five genera and three families, showed a statistically significant 'escape-toward-the-light' behavior when placed in the Y-maze. Our results provide compelling evidence of widespread dim-light UV vision in bats. © Museum and Institute of Zoology PAS.
Paxton K.L.,University of Southern Mississippi |
Paxton K.L.,University of Hawaii at Hilo |
Cohen E.B.,Smithsonian Conservation Biology Institute |
Paxton E.H.,Pacific Island Ecosystems Research Center |
And 2 more authors.
PLoS ONE | Year: 2014
Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in South America.
Vorsino A.E.,U.S. Fish and Wildlife Service |
Fortini L.B.,Pacific Island Ecosystems Research Center |
Amidon F.A.,U.S. Fish and Wildlife Service |
Miller S.E.,U.S. Fish and Wildlife Service |
And 4 more authors.
PLoS ONE | Year: 2014
Occupation of native ecosystems by invasive plant species alters their structure and/or function. In Hawaii, a subset of introduced plants is regarded as extremely harmful due to competitive ability, ecosystem modification, and biogeochemical habitat degradation. By controlling this subset of highly invasive ecosystem modifiers, conservation managers could significantly reduce native ecosystem degradation. To assess the invasibility of vulnerable native ecosystems, we selected a proxy subset of these invasive plants and developed robust ensemble species distribution models to define their respective potential distributions. The combinations of all species models using both binary and continuous habitat suitability projections resulted in estimates of species richness and diversity that were subsequently used to define an invasibility metric. The invasibility metric was defined from species distribution models with <0.7 niche overlap (Warrens I) and relatively discriminative distributions (Area Under the Curve >0.8; True Skill Statistic >0.75) as evaluated per species. Invasibility was further projected onto a 2100 Hawaii regional climate change scenario to assess the change in potential habitat degradation. The distribution defined by the invasibility metric delineates areas of known and potential invasibility under current climate conditions and, when projected into the future, estimates potential reductions in native ecosystem extent due to climate-driven invasive incursion. We have provided the code used to develop these metrics to facilitate their wider use (Code S1). This work will help determine the vulnerability of native-dominated ecosystems to the combined threats of climate change and invasive species, and thus help prioritize ecosystem and species management actions.
Some of Hawaii’s most iconic birds are experiencing dangerous declines — and a combination of mosquitoes and climate change seems to be the culprit. A study published Wednesday in the journal Science Advances suggests that mosquito-borne diseases, including avian malaria, have helped cause rapid declines in nearly all the native bird species on the Hawaiian island of Kaua’i. The researchers suggest that rising temperatures have allowed mosquitoes to expand into the birds’ high-elevation ranges, which were once too cool for them to tolerate — and as temperatures continue to heat up on the island, the situation will likely only worsen. The study focuses on eight bird species native to Kaua’i, all of which are found only in the Hawaiian islands. Six of these species belong to a group of birds known as “honeycreepers” — a colorful and diverse group that has existed on the Hawaiian archipelago for millions of years. While there were once dozens of honeycreeper species found throughout the islands, more than half of them have gone extinct as a result of habitat degradation, invasive species and disease. The other two species included in the study were a rare species of thrush and a type of bird known as a monarch flycatcher. All of these species tend to be found at high elevations on the island, explained Eben Paxton, an avian ecologist with the U.S. Geological Survey’s Pacific Island Ecosystems Research Center and the new study’s lead author. This is typical of Hawaiian forest birds in general. The farther the birds go up the islands’ mountains and plateaus, the more protected they are from habitat destruction, invasive predators and non-native birds that might compete with them for resources at lower elevations. Higher elevations are also cooler, and therefore less conducive to mosquitoes and the diseases they carry. Native Hawaiian birds — particularly the honeycreepers — tend to be highly susceptible to avian malaria, which arrived on the islands only in recent history, long after the birds had evolved there. It’s believed that mosquitoes were first carried to Hawaii some time in the mid-1800s, and diseases like the malaria and avian pox began showing up afterward. Conservationists believe that mosquito-borne diseases now pose a major threat to the honeycreepers’ future. And the new study helps confirm those fears. The researchers used survey data to assess changes in the birds’ populations over the past three decades. They found that all of the honeycreeper species had experienced rapid declines throughout their ranges — by up to 94 percent at the edges of their ranges and up to 68 percent in the core areas. The flycatcher, on the other hand, exhibited mixed trends — decreasing around the outer parts of its range and increasing substantially toward the core areas of its territory. There was not enough data on the rare thrush to make an adequate assessment of its population changes. While the researchers believe many factors are likely contributing to the birds’ declines, the results make a good case for the idea that disease is one of the biggest culprits. Threats such as predators or competing bird species tend to be most pronounced around the peripheries of the native birds’ ranges. But the honeycreepers exhibited marked declines throughout their ranges, not just at the edges. Furthermore, the fact the honeycreepers had experienced the worst declines, while the monarch flycatcher was in comparatively better shape, was also telling, according to Paxton. Previous research has suggested that the flycatcher is less susceptible to malaria than the honeycreepers. The researchers believe climate change has played a key role in the growing influence of mosquito-borne diseases. Research has suggested that the prevalence of avian malaria in the upper elevations of Kaua’i has more than doubled since the 1990s, and that this increase has corresponded with climatic changes in the area. “Naturalists working up in the Kaua’i mountains very rarely ever saw mosquitoes, even despite extensive searches for [them],” Paxton noted. “And just in the last five to six years, researchers that are working up in those mountains are now seeing mosquitoes commonly.” The researchers worry that if action isn’t taken soon, continued declines could lead to the extinction of these native birds. Two species in particular — the ‘akikiki and the ‘akeke‘e — currently pose a special concern, with fewer than a thousand individuals left of each. “We feel like in the next five to 10 years, those species will go extinct without major intervention,” Paxton said. And the other honeycreepers may not be far behind. As a result, mosquito control efforts are among the biggest priorities for conservationists. These can include traditional control methods, such as eliminating standing water, as well as more cutting-edge techniques, such as releasing genetically modified mosquitoes that cause populations to die back over time. It’s a technique that’s currently being applied in places like Brazil to combat Zika. Additionally, tackling some of the other factors affecting the bird — cracking down on invasive species, like rats, for instance, which prey on the birds’ nests — could also help slow the declines, Paxton added. The most important point is that action is needed quickly. The study demonstrates the unusually powerful impact of climate change on island ecosystems, showing how quickly these isolated species can be affected if strong measures aren’t taken to prevent them. “If we do nothing, then we will lose most of these species,” Paxton said. “So it’s really important that we as a country, as a society, come up with a strategy that we agree on to move forward against extinction.”
Farias M.E.M.,University of Hawaii at Hilo |
la Pointe D.A.,Pacific Island Ecosystems Research Center |
Atkinson C.T.,Pacific Island Ecosystems Research Center |
Czerwonka C.,University of Hawaii at Hilo |
And 2 more authors.
PLoS ONE | Year: 2010
Background: Avipoxvirus sp. is a significant threat to endemic bird populations on several groups of islands worldwide, including Hawaiì, the Galapagos Islands, and the Canary Islands. Accurate identification and genotyping of Avipoxvirus is critical to the study of this disease and how it interacts with other pathogens, but currently available methods rely on invasive sampling of pox-like lesions and may be especially harmful in smaller birds. Methodology/Principal Findings: Here, we present a nested TaqMan Real-Time PCR for the detection of the Avipoxvirus 4b core protein gene in archived blood samples from Hawaiian birds. The method was successful in amplifying Avipoxvirus DNA from packed blood cells of one of seven Hawaiian honeycreepers with confirmed Avipoxvirus infections and 13 of 28 Hawaiì àmakihi (Hemignathus virens) with suspected Avipoxvirus infections based on the presence of pox-like lesions. Mixed genotype infections have not previously been documented in Hawaiì but were observed in two individuals in this study. Conclusions/Significance: We anticipate that this method will be applicable to other closely related strains of Avipoxvirus and will become an important and useful tool in global studies of the epidemiology of Avipoxvirus.