Chasiempis Sandwichensis Research Articles

Twenty‐five years of change in forest structure and nesting behavior of Hawaiʻi ʻelepaio

Long‐term ecological studies are invaluable for detecting changes over time. Forest restoration has been a conservation priority in Hawaiʻi, where invasive species have negatively impacted native bird habitat. During 1993–1994, a study was conducted of Hawaiʻi ʻelepaio (Chasiempis sandwichensis) nest site selection and forest composition in mesic montane forest along Mauna Loa Road in Hawaiʻi Volcanoes National Park. We returned to the site and repeated the methods used in the earlier study to record Hawaiʻi ʻelepaio nest site selection (tree species, tree and nest height, and tree girth [diameter at breast height, DBH]) from 2015 to 2017, and measured forest composition (tree density, relative abundance, height, and DBH) in 2019. Three times as many nests were found in ʻaʻaliʻi (Dodonaea viscosa) as in koa (Acacia koa) in both time periods. Heights of koa and ʻaʻaliʻi did not change, but their DBH increased over time. The relative height of nests in ʻaʻaliʻi trees did not change, but nests in koa were placed higher in the crown during the later study. Overall tree density increased from 1,619 (95% confidence interval [CI] = 1,499–1,740) trees/ha to 2,583 (95% CI = 2,176–3,096) trees/ha. Koa relative abundance was 53% of total trees earlier and 45% later, ʻaʻaliʻi remained at 47%, and māmane (Sophora chrysophylla) increased from 0 to 8% over time. Our results indicate that changes in forest composition affect nesting behavior, but in ways that are not necessarily simple or consistent.

Response of Male Hawaii Elepaio Chasiempis sandwichensis to Conspecific Songs: A Small-Scale Playback Study

Las aves paseriformes aprenden sus cantos principalmente a traves de la transmision cultural. Sin embargo, la fragmentacion del habitat puede provocar una variacion cultural en el aprendizaje de cantos dando lugar a restricciones en la transmision de informacion cultural, incluyendo interacciones acusticas. En este estudio, nuestro objetivo es evaluar la respuesta individual a vocalizaciones de la misma especie dentro de dos poblaciones diferentes, asi como entre ambas poblaciones. Para ello, utilizamos reproducciones de cantos del monarca elepaio Chasiempis sandwichensis en un paisaje fragmentado que se encuentra en la ladera noreste del volcan Mauna loa (Isla de Hawai, EE.UU.). Evaluamos la respuesta de los machos de monarca elepaio a los cantos grabados en su misma poblacion, asi como en una poblacion diferente. Tambien comparamos vocalizaciones entre ambas poblaciones para evaluar diferenciacion acustica. Nuestros resultados indican divergencias comportamentales en la respuesta al canto de esta especie a pequena escala, asi como diferencias significativas en rasgos acusticos. Sin embargo, contrariamente a lo que se esperaba, los individuos de monarca elepaio de ambas poblaciones no variaron en su patron de respuesta a los cantos en funcion de su origen. Esto sugiere que la diferenciacion acustica puede no ser lo suficientemente fuerte como para dar lugar a una divergencia comportamental en la respuesta de los individuos de monarca elepaio, a pesar de la existencia de diferencias entre los rasgos acusticos de ambas poblaciones.

Increased nesting success of Hawaii Elepaio in response to the removal of invasive black rats

Abstract In Hawaii and other oceanic islands with few native land mammals, black rats (Rattus rattus) are among the most damaging invasive vertebrate species to native forest bird populations and habitats, due to their arboreal behavior and generalist foraging habits and habitat use. We evaluated the nesting response of Hawaii Elepaio (Chasiempis sandwichensis; Monarchidae), a generalist insectivore, to the removal of black rats using rodenticide in a before-after-control-impact study in high- and low-elevation mesic montane habitat recovering from long-term damage from introduced ungulates and weeds. We monitored nesting success and rat abundance during 2015–2016 before applying rodenticide bait in 2017 to remove rats from two 700 × 700 m treatment plots that were paired with 2 nontreatment plots of the same size. Rat abundance was reduced by 90% during treatment, with combined variables treatment and elevation best explaining the change using GLM methods and AIC model selection. The daily survival rate (DSR) of nests (n = 191) was greater on treated plots after rodenticide application (mean ± SE = 0.980 ± 0.004 treatment; 0.964 ± 0.004 nontreatment), modeled nest success increased from 29% to 50%, and apparent nest success (number of successful nests per total nests) increased from 37% to 52%. The most informative model for predicting DSR included the effect of treatment. Predation by rats was documented at 3 of 16 nests using video surveillance, and we observed additional evidence of rat predation during in-person nest monitoring. Rats targeted adults on the nest and sometimes removed intact eggs, leaving little trace of their activity. Our results demonstrate that reducing rat predation can immediately improve the nesting success of even a common bird species in habitat with a long history of forest restoration. Sustained predator control may be critical to accelerating the recovery of native forest bird communities.

Ecogeographic Patterns of Morphological Variation in Elepaios (Chasiempisspp.): Bergmann's, Allen's, and Gloger's Rules in a Microcosm

Abstract 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 propo...

Stepping stone speciation in Hawaii’s flycatchers: molecular divergence supports new island endemics within the elepaio

The elepaio (Chasiempis sandwichensis) is a monarch flycatcher endemic to the Hawaiian Islands of Kauai, Oahu, and Hawaii. Elepaio vary in morphology among and within islands, and five subspecies are currently recognized. We investigated phylogeography of elepaio using mitochondrial (ND2) and nuclear (LDH) markers and population structure within Hawaii using ND2 and microsatellites. Phylogenetic analyses revealed elepaio on each island formed reciprocally monophyletic groups, with Kauai ancestral to other elepaio. Sequence divergence in ND2 among islands (3.02–2.21%) was similar to that in other avian sibling species. Estimation of divergence times using relaxed molecular clock models indicated elepaio colonized Kauai 2.33 million years ago (95% CI 0.92–3.87 myr), Oahu 0.69 (0.29–1.19) myr ago, and Hawaii 0.49 (0.21–0.84) myr ago. LDH showed less variation than ND2 and was not phylogenetically informative. Analysis of molecular variance within Hawaii showed structure at ND2 (fixation index = 0.31), but microsatellites showed no population structure. Genetic, morphological, and behavioral evidence supports splitting elepaio into three species, one on each island, but does not support recognition of subspecies within Hawaii or other islands. Morphological variation in elepaio has evolved at small geographic scales within islands due to short dispersal distances and steep climatic gradients. Divergence has been limited by lack of dispersal barriers in the extensive forest that once covered each island, but anthropogenic habitat fragmentation and declines in elepaio population size are likely to decrease gene flow and accelerate differentiation, especially on Oahu.

Importance of Nest Predation by Alien Rodents and Avian Poxvirus in Conservation of Oahu Elepaio

ABSTRACT The Oahu elepaio (Chasiempis sandwichensis ibidis) is an endangered forest bird endemic to the Hawaiian island of Oahu (USA) and is threatened by nest predation from alien rodents and mosquito‐borne diseases. I investigated importance of these threats and evaluated success of conservation efforts from 1995 to 2008. I controlled rodents with snap‐traps and bait stations in 3 valleys and switched sites from non‐treatment to treatment over time. I mist‐netted and color‐banded 91 elepaio, inspected them for symptoms of avian poxvirus (Poxvirus avium), and estimated survival using multistate mark‐recapture models. I determined annual fecundity of each breeding pair and monitored success of 212 nests. The oldest known Oahu elepaio was ≥15 years old. Survival of females was higher with rodent control (0.82 ± 0.05) than without (0.55 ± 0.12), but survival of males was not affected by rodent control (0.86 ± 0.02 with vs. 0.84 ± 0.04 without). Survival of elepaio with active or inactive pox‐like lesions was 4–10% lower than survival of elepaio with no pox symptoms. Rodent control resulted in higher annual fecundity (0.69 ± 0.05 vs. 0.33 ± 0.06 fledglings/pair) and nest success (62% vs. 33%). Female site‐fidelity, mate fidelity, and female encounter probability were lower in the absence of rodent control because more females switched territories and mates after nest failure. Population growth calculated from survival and fecundity estimates was stable with rodent control (1.07 ± 0.04) but declining without rodent control (0.69 ± 0.05). Elepaio numbers have continued to decline despite rodent control, probably because some young birds disperse into adjacent unmanaged areas that act as sinks. The best immediate management strategy for Oahu elepaio is to conduct rodent control over larger areas. Restoration of native forest would benefit elepaio by providing nest sites that are less attractive to rodents. Construction of predator‐proof fences and eradication of predators would provide the best long‐term protection for elepaio.

BIOGEOGRAPHY OF `ELEPAIO: EVIDENCE FROM INTER-ISLAND SONG PLAYBACKS

Abstract I used inter-island song playbacks and information on geology, ecology, and behavior to investigate biogeography and species limits in the `Elepaio (Chasiempis sandwichensis), a monarch flycatcher (Monarchidae) endemic to the Hawaiian Islands. `Elepaio occur on Kaua`i, O`ahu, and Hawai`i, but are absent on the four islands of the Maui Nui group in the center of the Hawaiian Archipelago. It is unlikely that `Elepaio became extinct on Maui Nui or were excluded by the presence of competing species. `Elepaio are absent in the fossil record on all four islands of Maui Nui, but occur in the fossil record on all three islands they currently inhabit. They have adapted to a variety of forested habitats and are more resistant to alien diseases than other bird species that have persisted on Maui Nui. `Elepaio on each island responded most strongly to songs from their own island. Response to foreign songs was asymmetrical. Hawai`i `Elepaio responded to songs from Kaua`i, suggesting that `Elepaio on Kaua`i an...

Diversity, origins and virulence of Avipoxviruses in Hawaiian Forest Birds

We cultured avian pox (Avipoxvirus spp.) from lesions collected on Hawai‘i, Maui, Moloka‘i, and ‘Oahu in the Hawaiian Islands from 15 native or non-native birds representing three avian orders. Phylogenetic analysis of a 538 bp fragment of the gene encoding the virus 4b core polypeptide revealed two distinct variant clusters, with sequences from chickens (fowlpox) forming a third distinct basal cluster. Pox isolates from one of these two clusters appear closely related to canarypox and other passerine pox viruses, while the second appears more specific to Hawai‘i. There was no evidence that birds were infected simultaneously with multiple pox virus variants based on evaluation of multiples clones from four individuals. No obvious temporal or geographic associations were observed and strict host specificity was not apparent among the 4b-defined field isolates. We amplified a 116 bp 4b core protein gene fragment from an ‘Elepaio (Chasiempis sandwichensis) collected in 1900 on Hawai‘i Island that clustered closely with the second of the two variants, suggesting that this variant has been in Hawai‘i for at least 100 years. The high variation detected between the three 4b clusters provides evidence for multiple, likely independent introductions, and does not support the hypothesis of infection of native species through introduction of infected fowl. Preliminary experimental infections in native Hawai‘i ‘Amakihi (Hemignathus virens) suggest that the 4b-defined variants may be biologically distinct, with one variant appearing more virulent. These pox viruses may interact with avian malaria (Plasmodium relictum), another introduced pathogen in Hawaiian forest bird populations, through modulation of host immune responses.

Isolation and characterization of polymorphic microsatellite loci in the Hawaiian flycatcher, the elepaio (Chasiempis sandwichensis)

AbstractThirteen polymorphic microsatellite loci were isolated and characterized from two clades of an endemic Hawaiian flycatcher, the elepaio (Chasiempis sandwichensis). Seven dinucleotide repeats and one trinucleotide repeat were cloned from Kauai elepaio; five dinucleotide repeats were cloned from Oahu elepaio. Polymorphism was assessed in a sample of Oahu elepaio (n = 22) revealing two to 16 alleles per locus. Observed heterozygosity ranged from 0.14 to 0.91. However, linkage analysis exposed highly significant linkage disequilibrium between two of the most polymorphic loci. Twelve loci are therefore expected to be useful for investigations of population structure.

Facilitating the evolution of resistance to avian malaria in Hawaiian birds

Research has shown that avian malaria plays an important role in limiting the distribution and population sizes of many Hawaiian birds, and that projected climate change is likely to eliminate most disease-free habitat in Hawai’i in the next century. I used a modeling approach, parameterized with demographic data from the literature and the field, to examine alternate management scenarios for the conservation of native Hawaiian birds. I examined the feasibility of using management in the form of rodent control to facilitate the evolution of resistance to malaria by increasing the survival and reproduction of native birds. Analysis of demographic data from seven native species, Akepa ( Loxops coccineus), ‘Akohekohe ( Palmeria dolei), Elepaio ( Chasiempis sandwichensis), Hawai’i’amakihi ( Hemignathus virens), Hawai’i creeper ( Oreomystis mana), Omao ( Myadestes obscurus), and Palila ( Loxioides bailleui), suggest that differences in life history cause some species to be more susceptible to local extinctions from the transmission of malaria. Modeling results demonstrated that rodent control at middle, but not high, elevations can facilitate the evolution of resistance to malaria in several species of Hawaiian birds. Advocating a management approach that encourages evolutionary change in endangered species contrasts with the traditional conservation paradigm but it may be the best strategy to reduce the impacts of one of the multiple stressors that have devastated the native bird community of Hawai’i.

‘Elepaio “anting” with a garlic snail and a Schinus fruit

Abstract Anting is a widespread but poorly understood behavior in which birds apply ants or other organisms or objects to their plumage or skin. I observed two instances of active anting in the ‘Elepaio (Chasiempis sandwichensis), a monarch flycatcher endemic to the Hawaiian Islands, one involving a garlic snail (Oxychilus alliarius) and the second involving a fruit of Brazilian pepper or Christmas berry (Schinus terebinthifolius). On both occasions the ‘Elepaio held the object in its bill and wiped it on its body then preened, but did not eat the object. Chemical compounds contained in each species are known to have antibiotic properties, suggesting the purpose of the anting was to control parasites or pathogens. There are no native ants in Hawaii, and neither the garlic snail nor Brazilian pepper is native to Hawaii.

DEMOGRAPHY OF HAWAI‘I ‘ELEPAIO: VARIATION WITH HABITAT DISTURBANCE AND POPULATION DENSITY

From 1994 to 1997, I monitored ‘Elepaio (Chasiempis sandwichensis), a forest bird endemic to Hawaii, in three sites that differed in either degree of habitat disturbance or population density. The goal was to determine whether areas with disturbed forest and reduced population density due to disease were lower-quality habitats that acted as population sinks. Sites where the forest had been disturbed by cattle grazing and timber harvesting contained larger ‘Elepaio territories, supported less dense ‘Elepaio populations, and had a higher proportion of subadult birds in the breeding population and, thus, can be considered lower-quality habitat for ‘Elepaio. However, ‘Elepaio populations in disturbed sites did not have lower survival, reproduction, or site fidelity than a population in denser forest, and they were self-sustaining. Disturbed sites were not population sinks maintained by immigration; they simply had a lower carrying capacity. Annual survival of territory-holders was high and was slightly higher in males (0.86 ± 0.04 [mean ± 1 se]) than in females (0.79 ± 0.05). Fecundity was low, with pairs producing 0.56 ± 0.06 fledglings per year. Site fidelity was high in males (0.98) and females (0.93), and most birds remained on the same territory for the duration of the study or until their presumed death. Population growth was stable at two sites (λ = 0.96 ± 0.03, 1.02 ± 0.04) and increasing (1.12 ± 0.04) at a site recovering from an epizootic of avian poxvirus. Young, subadult-plumaged males defended smaller territories and produced fewer fledglings than older males, but female age did not affect territory size or reproductive success. Recruitment age was younger where population density was lower.

‘Elepaio subadult plumages reduce aggression through graded status-signaling, not mimicry

The 'Elepaio (Chasiempis sandwichensis) is a monarch flycatcher endemic to the Hawaiian Islands. Both sexes have a two-year delay in plumage maturation, with distinct first-year and second-year subadult plumages. This study tested hypotheses for the evolution of delayed plumage maturation in 'Elepaio by presenting adult males with models representing different ages and sexes in the breeding and nonbreeding seasons. The subadult plumages of 'Elepaio appeared to serve as honest, graded signals of status that reduced aggression from dominant adults. Both first-year and second-year subadult male models were attacked less than adult male models, and aggression increased linearly with age of male models. Neither subadult plumage appeared to function in sexual mimicry or juvenile mimicry. Second-year male models were attacked more than adult female models; neither subadult plumage resembles adult plumage of the opposite sex. First-year male models, which are juvenile-like, were not attacked more than adult female models, but juvenile mimicry cannot account for the behavior toward second-year male models and is a less parsimonious explanation. Aggression toward models was much higher in the breeding season, and all models were treated similarly in the nonbreeding season, suggesting competition for mates has been the primary selective force shaping the evolution of the 'Elepaio's plumage coloration. Models made from color pho- tocopies can be a useful alternative to museum specimens in behavioral studies of rare species or those in which damage to specimens during model presentation would occur.

Effects of alien rodent control on demography of the O'ahu 'Elepaio, an endangered Hawaiian forest bird

The O'ahu 'Elepaio Chasiempis sandwichensis ibidis is an endangered monarch flycatcher endemic to the Hawaiian island of O'ahu. Nest predation by alien Black Rats Rattus rattus is one of the main causes of the decline of this forest bird. From 1996 to 2000 we monitored demography of the largest remaining O'ahu 'Elepaio population and we controlled rats with snap traps and poison bait stations in an attempt to begin recovery of the species. Nest predation by Black Rats influenced many aspects of 'Elepaio demography. Rat control resulted in a 112% increase in 'Elepaio reproduction, a 66% increase in survival of female 'Elepaio, and restored mate fidelity, site fidelity, female age structure, and female recruitment age to more natural conditions. The 'Elepaio population growth rate (lambda) was 0.76 without rat control and 1.00 with rat control, indicating rat control stabilized 'Elepaio populations, but was not sufficient to cause population increase due to the added threat of alien mosquito-borne diseases. Rat control may facilitate evolution of disease resistance by providing birds that have greater natural immunity an increased chance of reproducing, thereby increasing the proportion of resistant birds in each subsequent generation more quickly.

Two-Year Delay in Plumage Maturation of Male and Female ‘Elepaio

Abstract I studied molt and plumage in the ‘Elepaio (Chasiempis sandwichensis), a monarch flycatcher endemic to the Hawaiian Islands, at Hakalau Forest National Wildlife Refuge on the island of Hawai‘i from 1994–1997. I captured birds in mist nets, examined them for molt, measured their plumage color with Munsell color chips, and followed them for several years to document plumage changes. Male and female Hawai‘i ‘Elepaio exhibited three distinct post-juvenal plumages, first basic, second basic, and definitive basic, and thus have a two-year delay in plumage maturation. ‘Elepaio have a single annual molt, so there are no alternate plumages. The first prebasic molt is partial, but all subsequent molts are complete. The first basic plumage is juvenile-like and sexually monochromatic. The second basic and definitive basic plumages are sexually dimorphic in throat color. In each sex the second basic plumage resembles definitive plumage. Age-related plumage changes include increases in the whiteness, number, a...

Ecology and Breeding Biology of the Hawaii Elepaio (Chasiempis sandwichensis bryani)

Elepaio (Chasiempis sandwichensis bryani) were studied on the island of Hawaii from 1970 through 198 1. The species had a protracted breeding season from February through August, with most intensive breeding from April to June. Annual breeding season length varied among years (range 3-7 months). Elepaio retained mates for more than one season and remained in their territory throughout the year. An Elepaio territory encompassed the nest site, all food resources, and had similar boundaries in succeeding years. Nests were statant, open-cupped, with mamane (Sophora chrysophylla) trees the preferred nesting sub- strate. Clutch size of 23 nests was two eggs and did not vary among years. Both parents incubated, brooded, and fed the young. Incubation periods averaged 18 (range 17-l 9) days; hatching success of eggs incubated to term in 22 nests was 75%. Nestling periods averaged 15.6 days; fledging success was 89.3% and young fledged synchronously. Total reproductive success, based on 19 nests with complete records, was 65.8%. The most important factor that influenced annual Elepaio productivity on Mauna Kea was length of the breeding season, followed by the number of nesting birds and eggs laid that failed to hatch (25%). Inter-island subspecies comparisons revealed many similar behaviors (e.g., courtship chasing, territory type, clutch and egg sizes, nest placement, adult roles in nest building, incubation, brooding and feeding). Differences among subspecies appeared to revolve mainly around the influences of forest-type in which birds bred. In mesic habitats on Oahu and Hawaii, predation of eggs and young by introduced mammals played a major role in decreasing annual productivity, whereas in the dry forest of Mauna Kea predation on C. s. bryani nests was much lower.

Intraspecific Variation in Elepaio Foraging Behavior in Hawaiian Forests of Different Structure

I studied intraspecific variation in foraging behavior of an endemic, insectivorous bird, the Elepaio (Chasiempis sandwichensis), in two Hawaiian forests that differed in degree of human modification. The undisturbed forest had a closed canopy, a dense understory, and a groundcover of native plants. The disturbed forest had much lower tree and shrub densities, and a ground cover of alien grasses. Search-and-attack rates, proportions of attack maneuvers, and proportional substrate use differed between habitats. Birds in disturbed habitat attacked prey two-thirds as often as birds in undisturbed habitat, hopped less frequently, and flew farther and more often. They also did less perch-gleaning and chasing, did more flight-gleaning and hawking, used small branches and the ground less often, and used leaves and the air more often than birds in undisturbed habitat. Disturbed areas may be lower-quality foraging habitat because they require more difficult foraging methods. Age was associated with variation in search-and-attack rates and proportions of attack maneuvers, but sex was not. Subadult Elepaio attacked prey less often than adults, searched more slowly, and used simpler maneuvers more often, possibly to compensate for their lower proficiency. Log-linear analysis showed that attack maneuver was related to substrate and to tree species. Birds perch-gleaned more often on twigs and in ohia (Metrosideros polymorpha), hung more often on bark and in koa (Acacia koa), and flight-gleaned more often on leaves. Elepaio showed much flexibility in foraging behavior and used more-diverse attack maneuvers and substrates than related continental species, which may allow Elepaio to exploit disturbed habitats successfully.

Scales of Habitat Selection by Foraging 'Elepaio in Undisturbed and Human-Altered Forests in Hawaii

I examined habitat selection by foraging 'Elepaio (Chasiempis sandwichensis) in relatively undisturbed and human-altered forests in Hawaii at three hierarchically-nested scales by comparing birds with random sites. The fine scale was based on a sphere with a radius of 0.75 m, the intermediate scale used a cylinder from ground to canopy with a radius of 1.5 m, and the broad scale was based on the point-quarter method. At a fine scale, 'Elepaio in both forests selected foraging sites with high foliage density, large bark surface area, and many twigs and branches. 'Elepaio in disturbed areas compensated for lower available foliage density by being "hyperselective" toward high density sites. At an intermediate scale, 'Elepaio in both forests favored sites with above average foliage density at all heights. Birds in undisturbed habitat preferred sites with native ground cover and used sites with feral pig damage or exotic grasses less than expected, while birds in disturbed forest did not favor any ground cover type. At a broad scale, tree and shrub densities were much lower in disturbed areas, but 'Elepaio did not select sites with high tree or shrub density in either forest. 'Elepaio in both forests preferred 'Ohia, and used Koa less than expected. Disturbed areas may be lower quality foraging habitat because less space consists of sites with preferred high fine-scale foliage density. The broad scale is commonly used to measure habitat around nest sites and song perches, but it did not detect patterns of foraging site selection and may be too coarse for measuring foraging habitat of forest birds.

Intra-Island Variation in the 'Elepaio on the Island of Hawai'i

The 'Elepaio (Chasiempis sandwichensis) exhibits great vari- ation in plumage color on the Island of Hawai'i. Analysis of specimens from localities throughout the island reveals that the variation is geographically based, and that three subspecies can be distinguished: C. s. bryani, a pale form found at high elevation on the southwestern slopes of Mauna Kea; C. s. ridgwayi, a dark form found in wet windward forests; and C. s. sandwich- ensis, an intermediate form found in forests of the Kona region. Several zones of primary intergradation and one of possibly secondary intergradation occur, but appear to be narrow. The forms C. s. sclateri of Kaua'i and C. s. gayi of O'ahu exhibit no similar intra-island variation. Variation among the Hawai'i subspecies probably evolved in response to local variation in rainfall, and follows the predictions of Gloger's Rule, but the selective forces involved are obscure. The 'Elepaio (Chasiempis sandwichensis) is a monarchine flycatcher that comprises a genus endemic to the Hawaiian Islands. 'Elepaios occur on Kaua'i, O'ahu, and Ha- wai'i, but are enigmatically absent from oth- er seemingly suitable islands. Great plum-

The Use of Sheep Wool in Nest Construction by Hawaiian Birds

The use of sheep wool as a nesting material was examined from 1969 through 1975 on the island of Hawaii. Of the 10 bird species studied, six used wool in their nests. Both introduced and endemic birds use wool, with a significantly greater usage by endemic birds. Use of wool in nests appears correlated with the intricacy of a species' nest, with significant differences between degree of usage in complex and simple nests. Roughly built nests, like those of the Cardinal (Cardinalis cardinalis), contained no wool whereas the complex nests of the Elepaio (Chasiempis sandwichensis) had a great deal of it. Birds apparently use wool because of its ready availability and its binding quality. They gathered it from tufts that snag on branches as the sheep pass or from dried skins. The amount of wool in each nest varied both interspecifically and intraspecifically, but in all nests only the body contained wool; the lining was always of other material. A separate study compared an area void of sheep and an adjacent one containing sheep to determine if wool is a preferred and sought-after material. Only the Elepaio was found consistently to travel distances to procure it; the other species used it only when available within their territories.