Habitat relationships of forest birds on Tutuila Island, American Samoa

Abstract

Aim Our knowledge of landbirds on tropical Pacific islands is often comprised of brief, one-time surveys. We know little of species' habitat preferences, and this information is critical for understanding the resource requirements or population status of native species and the impacts of human activity on island birds.Location Tutuila Island, American Samoa. MethodsThe spatial patterns in forest birds were investigated. This island harbours large tracts of native forest, a variety of disturbed and non-native forests, and some relatively healthy bird populations. The distribution of birds was correlated with forest types using habitat data collected at fifty-seven sites and avian census data collected monthly for 1-4 years at these sites. ResultsDifferences in location and in vegetation structure and composition between native and non-native habitats are important influences on the distribution of birds on Tutuila. Among native species, for example, the purple-capped fruit-dove (Ptilinopus porphyraceus Temminck) is dependent upon native habitat, the Samoan starling (Aplonis atrifusca Peale) occurs in all habitats, and the cardinal honeyeater (Myzomela cardinalis Gmelin) is more abundant in low elevation, non-native habitat.Conclusions This research reinforces the importance of quantitative assessment of habitat relationships in the study and conservation of Pacific birds.

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

“…Freifeld (1999) suggests that wattled honeyeaters may attempt to exclude cardinal honeyeaters from Erythrina in native-forest habitats. We did not observe inter-specific chases among wattled and cardinal honeyeaters, although an intraspecific chase between two cardinal honeyeaters was recorded at a rural plantation tree.…”

“…Human-introduced exotic birds are well established on Tutuila, but have not yet spread to outlying Ofu, Olosega and Ta'u (Watling 2004). Freifeld (1999Freifeld ( , 2004 has investigated the habitat relationships of avifauna on Tutuila, and there has been considerable research on the feeding behaviour of American Samoa's fruit bats (Banack 1996Nelson et al 2000a Nelson et al , b, 2005Brooke 2001;Banack and Grant 2002). Few data are available that describe the interactions between exotic and native species at key indigenous nectar sources in American Samoa.…”

“…Erythrina variegata nectar is an important food for American Samoa's native fruit bats and honeyeaters Freifeld 1999;Webb et al 1999). Dysoxylum maoto and Dysoxylum samoensis provide foods favoured by the native Pacific pigeon .…”

“…Bulbuls and mynas are found only on Tutuila. Researchers indicate a need for data regarding behaviour and competition among native birds and exotic bulbuls for native food sources (Freifeld 1999;Watling 2004), and detailing the feeding behaviour of fruit bats at nectar sources . This study presents data on these matters.…”

“…In addition to inserting their beaks into Erythrina flowers, we also observed them eating flowers. Bulbuls outside their native range often are described as limited to human-modified habitats (Freifeld 1999;Eguchi and Amano 2004;Watling 2004; Yap and Sodhi 2004;Peh et al 2006), however, on Oahu, Hawai'i, they have spread into undeveloped areas once used exclusively by native birds (McAllan and Hobcroft 2005), tripling their range in only six years (van Riper et al 1979; Williams and van Giddings 1984). We observed the greatest frequency of bulbuls in trees on a rural plantation 8 km from the nearest village.…”