We studied populations of introduced rats in three areas in Hawaiian rainforests as part of a larger study to determine the factors limiting endangered bird populations. Species composition among 1 264 rats live trapped was Black Rats Rattus rattus 60.8%, Polynesian Rats R. exulans 38.1 %, and Norway Rats R. norvegicus 1.0%. Capture rates did not differ among the three study areas or four seasonal periods for any of the species. Males comprised 53.0% of 921 Black Rats and 55.3% of 783 Polynesian Rats that were sexed. Juvenile rats comprised 26.2% of Black Rats and 31.7% of Polynesian Rats captured and weighed. Black and Polynesian Rats reproduced throughout the year, but the highest proportion of juveniles in the population was captured in September-November and the lowest proportion in April-June. Mean home range size was 3.6 ha for four Black Rats (three males and one female) and 3.0 ha for three Polynesian Rats (two males and one female). All daytime nests of Black Rats found were above ground, generally in cavities within tree canopies. Mean annual rat activity in tree canopies as measured with tracking tunnels was 43% (range 21?80%). Of 44 rats captured in trees, 43 were Black Rats and one was a Polynesian rat.

No abstract

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.

Feral cat Felis catus home range in a Hawaiian montane wet forest and their diet in three habitats - montane wet forest, subalpine dry forest, and lowland dry forest ? were determined to provide baseline ecological data and to assess potential impacts to native terrestrial fauna. Seven cats (three males and four females) were captured in 624 trap nights. Mean weight of adult cats was 2.85 � 0.27 (SE) kg for males and 1.87 � 0.03 kg for females. Mean diurnal home range using the adaptive kernel method was 5.74 � 2.73 km2 for three males and 2.23 � 0.44 km2 for two females. Daytime locations were always within the montane wet forest with the borders on one or more sides of the home ranges of all cats defined by open grassland pastures. Rodents comprised the majority of the cat diets in all three habitats, with the frequencies of occurrence between 0.88 and 0.91. Bird remains were a regular component of the diet of cats, with montane wet forest having the highest frequency of occurrence (0.68), followed by subalpine dry forest (0.53). and lowland dry forest (0.21).