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Honolulu, HI, United States

Animals often exhibit predictable geographic variation in morphology, and such ecogeographic patterns reflect local adaptation to varying environmental conditions. The most common of these patterns are termed Bergmann's, Allen's, and Gloger's rules. I studied morphological variation in the Hawaii Elepaio (Chasiempis sandwichensis) and the Oahu Elepaio (C. ibidis), forest birds endemic to the Hawaiian Islands. I measured body size and plumage color of 223 live elepaios captured at 36 sites on Hawaii and 132 live elepaios captured at 23 sites on Oahu, and I examined 132 museum specimens from an additional 22 locations on Hawaii. I used multiple regressions to examine relationships of elepaio body size and plumage color to elevation and annual rainfall on each island. Size of Hawaii Elepaios varied among sites and was related to elevation and rainfall. Wing chord, tail length, and body mass had positive relationships with elevation, as predicted by Bergmann's rule. Proportional bill length and proportional tarsus length were inversely related to elevation, as predicted by Allen's rule. In Hawaii Elepaios, 17 of 20 plumage color variables were related to rainfall. Elepaios in wetter areas were more heavily pigmented and had fewer and smaller white markings, as predicted by Gloger's rule. Plumage color of Oahu Elepaios showed similar but weaker patterns and only two of 20 plumage characters were related to rainfall. All body-size and plumage-color measurements had smoothly clinal distributions, with no large gaps with respect to elevation or rainfall. Putative subspecies of the Hawaii Elepaio differed in mean value of several plumage characters, but there was overlap in plumage color among subspecies and variation within them, and none of the three subspecies was diagnosable from both other subspecies by any plumage character using the 75% rule. Elepaios differed morphologically among sites only a few kilometers apart because of their sedentary behavior and the steep gradients in temperature and elevation and limited climatic variation of the tropical environment of the Hawaiian Islands. Morphological variation in elepaios is smoothly clinal because there are few dispersal barriers and elepaios inhabit areas with a range of climates and vegetation. Although my results did not support the designation of subspecies within the Hawaii Elepaio, morphological and underlying genetic variation is important, and conservation of elepaios with varying phenotypes would preserve evolutionary potential and ability to adapt to climate change. © The American Ornithologists' Union, 2011. Source

Reed J.M.,Tufts University | Desrochers D.W.,Dalton State College | Vanderwerf E.A.,Pacific Rim Conservation | Scott J.M.,The College of Idaho
BioScience | Year: 2012

One-third of the bird species listed under the US Endangered Species Act are endemic to Hawaii. One requirement of delisting a species is the elimination or abatement of threats to that species. More than 95% of Hawaii's threatened and endangered species face multiple threats that cannot be eliminated (e.g., alien mammalian predators, invasive alien plants that alter habitat structure, disease). However, because we can manage many of the threats at scales at which the achievement of recovery goals is possible, these species could be delisted if conservation partners committed to the implementation of stewardship agreements to maintain viable populations following those populations' delistings. © 2012 by American Institute of Biological Sciences. All rights reserved. Request permission to photocopy or reproduce article content at the University of California Press's Rights and Permissions Web site at . Source

Pitt W.C.,U.S. Department of Agriculture | Driscoll L.C.,U.S. Department of Agriculture | Vander Werf E.A.,Pacific Rim Conservation
Human-Wildlife Interactions | Year: 2011

The puaiohi or small Kauai thrush (Myadestes palmeri) is an endangered bird endemic to the island of Kauai, Hawaii. The sole population of about 500 birds is currently restricted to remote, higher elevation areas of the Alakai Plateau. Puaiohi nest primarily on steep streamside cliffs, and their distribution and abundance are limited by availability of suitable nesting sites. Black rats (Rattus rattus) cause nest failure and mortality of nesting female puaiohis, and ground-based rodent control has not been effective at reducing nest predation. In 2007, we investigated whether artificialnest structures might be a viable alternative to rodent control by testing nest-box designs to find one that was resistant to rats. In laboratory trials, we evaluated 3 designs that were currently being deployed as artificialnest boxes for puaiohi and found that they were not rat resistant. From these results, we developed and tested an improved design. Captive rats were unable to enter a nest box made from a 36-cm length of 15-cm-diameter plastic pipe with an overhanging entrance cut at an angle of 49°. Source

Vanderwerf E.A.,Pacific Rim Conservation
Conservation Biology | Year: 2012

The majority of bird extinctions since 1800 have occurred on islands, and non-native predators have been the greatest threat to the persistence of island birds. Island endemic species often lack life-history traits and behaviors that reduce the probability of predation and they can become evolutionarily trapped if they are unable to adapt, but few studies have examined the ability of island species to respond to novel predators. The greatest threat to the persistence of the Oahu Elepaio (Chasiempis ibidis), an endangered Hawaiian forest bird, is nest predation by non-native black rats (Rattus rattus). I examined whether Oahu Elepaio nest placement has changed at the individual and population levels in response to rat predation by measuring nest height and determining whether each nest produced offspring from 1996 to 2011. Average height of Oahu Elepaio nests increased 50% over this 16-year period, from 7.9 m (SE 1.7) to 12.0 m (SE 1.1). There was no net change in height of sequential nests made by individual birds, which means individual elepaios have not learned to place nests higher. Nests ≤3 m off the ground produced offspring less often, and the proportion of such nests declined over time, which suggests that nest-building behavior has evolved through natural selection by predation. Nest success increased over time, which may increase the probability of long-term persistence of the species. Rat control may facilitate the evolution of nesting height by slowing the rate of population decline and providing time for this adaptive response to spread through the population. © 2012 Society for Conservation Biology. Source

Van Der Werf E.A.,Pacific Rim Conservation | Young L.C.,Pacific Rim Conservation
Auk | Year: 2011

Accurate estimates of demographic rates are fundamental to understanding population dynamics and can provide insights into the ecology and conservation of a species. We used multistate mark-recapture models to estimate apparent annual survival, encounter probability, and life-stage transitions in Laysan Albatrosses (Phoebastria immutabilis) at Kaena Point, Hawaii, from 2003 to 2010. Four-state models of prebreeders, breeders, failed breeders, and skipped breeders overestimated survival by 1-3% and underestimated skipped breeding by 5-6%, but five-state models that included a state for unobserved skipped breeders performed better. Survival did not vary among years and was highest in prebreeders (mean ± SE = 0.996 ± 0.010) and lower in successful breeders (0.932 ± 0.023) than in failed breeders (0.963 ± 0.018), suggesting a cost to reproduction. Survival was similar in males and females among prebreeders, breeders, and failed breeders, but survival of males was lower among skipped breeders. Encounter probability was related to monitoring effort; more frequent visits and use of field-readable auxiliary bands and remote cameras resulted in higher encounter rates. With sufficient effort, all skipped breeders were observed at the colony even though they did not breed. Recruitment averaged 24% in females and 21% in males and varied among years. Breeding frequency averaged 0.807 ± 0.028 and varied among years. Successful breeders were more likely than failed breeders to skip the next breeding season. Estimates of all demographic rates except recruitment were similar to estimates for Laysan Albatrosses from Midway in the 1960s despite differences in methodology. This information can help measure population dynamics, breeding population sizes, population trends, and efficacy of conservation actions. © The American Ornithologists' Union, 2011. Source

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