Geology topics

Thane K. Pratt

Publications and source records attributed to Thane K. Pratt.

26 records · Page 2Linked to original sources

USGS2001

Home range and territoriality of two Hawaiian honeycreepers, the 'Akohekohe and Maui Parrotbill

Hawaiian honeycreepers have radiated into a diversity of trophic niches and patterns of space-use. We investigated space-use in two honeycreeper species, the ‘Ākohekohe ( Palmeria dolei ), an endangered nectarivore, and Maui Parrotbill ( Pseudonestor xanthophrys ), an endangered wood excavator, by mapping the home ranges and dispersion of color-banded individuals at a study site in relatively undisturbed montane cloud forest on Maui Island, Hawai‘i. With 20% of outlying points excluded, home-range size averaged much smaller for adult male ‘Ākohekohe (0.56 ha) than for male Maui Parrotbill (2.26 ha). In both species, a female's home range mostly overlapped that of her mate. Adult male Maui Parrotbill defended year-round home ranges from which they excluded conspecifics except for their mates and dependent offspring. Although our data suggest that ‘Ākohekohe also maintained all-purpose territories, the evidence is less convincing because these birds were seen feeding in the home ranges of other individuals. By defending all-purpose territories, these two species depart from the more common honeycreeper pattern of sharing large, undefended home ranges.

Condor↗

USGS2001

Newly emergent and future threats of alien species to Pacific birds and ecosystems

Although the devastating effects of established alien species to Pacific birds and ecosystems are generally well recognized by the avian conservation community, we raise the under appreciated issue of effects of incipient and future invasions. Although special attention to Pacific bird species “on the brink” is to a certain extent appropriate and necessary, a comparable focus on stopping new invasions appears desperately needed. All indications suggest that introductions will escalate with the trend toward ever increasing commerce and unrestricted trade unless stronger preventative measures are implemented very soon. The threat to Pacific island avifaunas from the brown tree snake ( Bniga irregularis ) is well-known, but as many as several hundred of the world’s snake species, some of which are repeatedly smuggled illegally as pets, might have similar impacts on native birds if transported to Pacific islands. We touch upon a sampling of obviously severe potential future threats, with the hope of raising awareness and resolve to fix the current woefully inadequate system for prevention of and rapid response to new invasions.

Studies in Avian Biology↗

USGS2001

The interplay of species concepts, taxonomy, and conservation: lessons from the Hawaiian avifauna

The Hawaiian Islands, with their unique geological history and geographic position, provide an excellent natural laboratory in which to evaluate currently competing biological (BSC) and phylogenetic (PSC) concepts of the species. Although the BSC as historically applied in archipelagic situations is shown to be flawed in producing overlumped polytypic species, it nevertheless remains the preferable concept for most practical purposes. A review of the taxonomic history and species limits in Hawaiian birds under both concepts reveals that, when properly applied, the BSC yields a species total remarkably close to that produced under the PSC, contrary to what many proponents of the latter have supposed. We propose that the widespread adoption of the PSC for conservation purposes is potentially harmful. The PSC trivializes the species taxon and introduces new problems of deciding when a population becomes diagnosable, the possibility that species could appear and disappear in a reticulate fashion, and the likelihood that genetically diagnosable but phenotypically identical, and therefore not field identifiable, populations could be ranked as species. All of these problems negatively impact such things as constructing credible and politically defensible lists of endangered species, the prioritization of limited conservation resources, and the gathering of field data. We contend the BSC is arguably a more rational concept that better supports the activities of both scientific and nonprofessional observers. Biological species limits in oceanic archipelagoes worldwide need to be reevaluated using modern concepts and technologies before rational conservation decisions can be made.

Hawaii↗

USGS2000

Reproductive ecology of the Maui Parrotbill

The endangered Maui Parrotbill ( Pseudonestor xanthophrys ) is an excavating, insectivorous Hawaiian honeycreeper endemic to the high elevation rain forests of east Maui, Hawaii. From March 1994 to June 1997, we studied various aspects of their breeding ecology. We color-banded 18 individuals, located and monitored 9 active nests, and took behavioral data during 440 hrs of nest observation. Both members of a pair maintained a year-round, all-purpose territory that included nest sites and food resources. Maui Parrotbill were monogamous within and between years; we found no evidence of polyandry, polygyny, or helpers at the nest. Nests were cup-shaped, composed mainly of lichen interlaced with small twigs, and positioned in the outer canopy forks of mature ohia ( Metrosideros polymorpha ) trees. Modal clutch size was one. Females performed most nest construction and all incubation and brooding; males provisioned females and assisted in feeding nestlings after their fourth day. Fledglings depended on parental care for 5–8 months, during which their bill strength increased and foraging skills improved. We calculated the overall nest success rate by the Mayfield Method as 0.42 for the 1995/1996 and 1996/1997 breeding seasons combined. Nest failure and fledgling disappearance coincided with events of high rainfall. Their breeding ecology most closely resembled the Akiapolaau ( Hemignathus munroi ), another excavating, insectivorous Hawaiian honeycreeper found on Hawaii Island. As with the Akiapolaau, the threat of extinction is persistent and results from both the constraints of inherent life history traits and artificial ecological changes. We advocate the protection and expansion of habitable forest areas and an ongoing program to monitor and mitigate the effects of invasive species.

Hawai'i↗

USGS1999

Eleutherodactylus frog introductions to Hawaii

As an oceanic archipelago isolated from continental source areas, Hawaii lacks native terrestrial reptiles and amphibians, Polynesians apparently introduced seven gecko and skink species after discovering the islands approximately 1500 years ago, and another 15 reptiles and five frogs have been introduced in the last century and a half (McKeown 1996). The Polynesian introductions are probably inadvertent because the species involved are known stowaway dispersers (Gibbons 1985; Dye and Steadman 1990), In contrast, most of the herpetological introductions since European contact with Hawaii have been intentional. Several frog species were released for biocontrol of insects (e.g., Dendrobates auratus , Bufo marinus , Rana rugosa , Bryan 1932; Oliver and Shaw 1953), and most of the remaining species are released or escaped pets (e.g., Phelsuma spp., Chamaeleo jacksonii , Iguana iguana , McKeown 1996), Government-approved releases have not occurred for many years, but the rate of establishment of new species has increased in the past few decades because of the importation and subsequent release of pets.

Hawaii↗

USGS1997

Status and management of the PaliIa, an endangered Hawaiian honeycreeper, 1987-1996

A single, relictual population of Palila Loxioides bailleui, a Hawaiian honeycreeper, survives on the slopes of Mauna Kea volcano on the island of Hawai'i, where it feeds principally on flowers and green seeds of the mamane tree Sophora chrysophylla. The Palila was listed as an endangered species by state and federal governments because of continuing damage to its habitat by browsing Feral and Mouflon Sheep Ovis aries and O. musimon and Goats Capra hircus and because of the bird's restricted range and low numbers. Ecology of the Palila was studied from 1987 to 1996. Annual population estimates fluctuated between 1 600 and 5 700 and averaged 3 400 birds. Estimates varied with availability of mamane seeds, which are less abundant in drought years. In drought years, most birds did not attempt to breed, and survival rates were lower because of a shortage of food. Availability of mamane seeds also showed large seasonal variability. While some nests were preyed upon by Owls Asio flammeus, Cats Felis catus and Rats Rattus rattus, losses were high at the end of the season from unexplained death of eggs and chicks. Genetic studies did not implicate inbreeding depression. Neither avian malaria nor avian pox appeared at this site, where the mosquito vector was absent. However, weather and food shortage worsened towards the end of the nesting season. Availability of food and habitat remain the principal factors limiting increase in the Palila population. Recovery efforts now focus on reducing numbers of feral ungulates, fire management, removing mammalian predators, and developing techniques for captive propagation and introduction to currently unoccupied sites within the bird's former range. Reforestation adjacent to the Mauna Kea Forest Reserve would allow the Palila population to expand and grow.

Pacific Conservation Biology↗

USGS1993

Status and population trends of Hawaii's native waterbirds, 1977-1987

Status and population trends of Hawaiis ’ native waterbirds were examined from 1977 through 1987. Waterbird population fluctuations were analyzed in relation to rainfall and land use dynamics. Numbers of Hawaiian Duck (Koloa) ( Anus wyvilliana ) and Hawaiian Common Moorhen ( Gallinula chloropus sandvicensis ) appeared stable over time; however, surveys were limited. Increase in Black-crowned Night-Heron ( Nycticorux nycticorux ) abundance appeared linked to expansion of aquaculture, particularly on Oahu, and not to climatic events. Annual rainfall patterns help explain and predict population fluctuations and anomalous distribution patterns involving Hawaiian American Coots ( Fulica americana alai ), moorhens, and Hawaiian Black-necked Stilts ( Himantopus mexicanus knudseni ). Coot, stilt, and moorhen populations fluctuated with climatic events, and intraisland dispersal to ephemeral wetlands occurred. Stilts exhibited regular inter-island migratory behavior, but coots dispersed in relation to major rainfall events. Seasonal fluctuation recorded for coots by past observers is the result of survey techniques not accounting for seasonal dispersal patterns.

Hawai'i↗

USGS1992

[Book review] Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part I. Non-Passeriformes [and] Part II. Passeriformes

Perhaps the great appeal of paleontological studies is that they inspire visions of past worlds richer and more interesting than our own. Yet, no matter how fascinating, these fossil creatures and their environments manifest a remoteness measured by more than geological time. But what if bones tell the story of a world that ought to still exist? In their long-awaited, twin monographs describing 32 species of subfossil birds from the Hawaiian Islands and commenting on the remains of perhaps as many as 22 other species, the authors more than double in size the recent endemic avifauna for this subtropical, oceanic archipelago.

The Auk↗