Habitat

An early account described the Bridled White-eye as occupying tall trees (42 Hartert, E. (1898). On the birds of the Marianne Islands. Novitates Zoologicae 5(1):51–69. Close ), whereas Stott (43 Stott, K. (1947). Notes on Saipan birds. Auk 64(4):523–527. Close ) found flocks on Saipan in a sugarcane field, in Casuarina equisitifolia stands, and in semi-wooded hillsides. Another early account described the species as being a habitat generalist although preferring trees and shrubs that have small leaves (2 Marshall, J. T. (1949). The endemic avifauna of Saipan, Tinian, Guam and Palau. Condor 51(5):200–221. Close ). More recently, the habitat of the Bridled White-eye has been described as shrubby forests, native Pandanus woods, and limestone forests, as well as introduced tangantangan (Leucaena leucocephala) thickets (44 Pratt, H. D., P. L. Bruner, and D. G. Berrett (1987). A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press, Princeton, NJ, USA. Close ).

On Guam, it was initially thought to prefer small bushes at roadsides and other waste places (17 Seale, A. (1901). Report of a mission to Guam. Occasional Papers of Bernice P. Bishop Museum 1:17–128. Close ). Baker (1 Baker, R. H. (1951). The avifauna of Micronesia. Its origin, evolution, and distribution. University of Kansas Publications, Museum of Natural History 3(1):1–359. Close ) reported it from uplands and in mature native cliff line forests of the northernmost part of the island. Tubb (45 Tubb, J. A. (1966.) Notes on birds of Guam. Natural History Bulletin of the Siam Society 21:135-138. Close ) found it in scrub, Stophlet (7 Stophlet, J. J. (1946). Birds of Guam. Auk 63(4):534–540. Close ) found it the volcanic soil-derived grasslands and foothills of south central Guam, and King (46 King, B. (1962). Guam field notes. Elepaio 23:29−31. Close ) observed it in coastal strands near Tarague Beach. It was once common in the Agana Swamp, and it was apparently also once common in the mixed woodland and second growth of the northern plateau. As the species became rare, it was present primarily in the mature, native cliff-line forest of extreme northwestern Guam, although it was still seen rarely in coastal strands near Pati Point Beach (16 Jenkins, J. M. (1983). The native forest birds of Guam. Ornithological Monographs 31:1–61. Close ).

On Saipan, the species was studied in two principal habitats that it occupied, native limestone forest and introduced tangantangan thickets. Of these two habitats, it was far more common in the former (47 Craig, R. J. (1996). Seasonal population surveys and natural history of a Micronesian bird community. Wilson Bulletin 108(2):246–267. Close , 48 Craig, R. J. (2021). The structure and dynamics of endangered forest bird communities of the Mariana Islands. Pacific Science 75:543−559. Close ). Limestone forest in the Marpi region is dominated by such native canopy trees as Guamia [= Meiogyne] mariannae, Neisosperma oppositifolia, Ochrosia mariannensis, Melanolepsis multiglandulosa, Cynometra ramiflora, Ficus prolixa, Pisonia grandis, Psycotria mariana, Aidia cochinchinensis Premna obtusifolia, Morinda citrifolia, Guettarda speciosa, Pandanus spp. and Erythrina variegata. In the Talufofo and Mt. Tapotchau regions, such native trees as Artocarpus mariannensis, Cerbera dilatata, Hernandia nymphaeifolia, Hibiscus tiliaceus, Mammea odorata and Barringtonia asiatica are also common. Near the summit of Mt. Tapotchau, birds frequented Pandanus spp. copses. Canopy height is generally restricted to <15 m because of frequent typhoons and understory vegetation is dense (49 Craig, R. J. (1989). Observations on the foraging ecology and social behavior of the Bridled White-eye. Condor 91(1):187–192. Close ). Such native forests are typical of the relatively xerophytic forest communities of the Mariana Islands of Saipan, Tinian, and Aguiguan where the Bridled White-eye is abundant (50 Chandran, R., R.J. Craig, Z. Keys, C. Sheu and J. Dubrall. (1992). Structure and composition of native forest on Aguiguan. Proceedings, Marianas Research Symposium 1:51-56. Close , 51 Craig, R.J. (1992). Ecological characteristics of a native limestone forest on Saipan, Mariana Islands. Micronesica 25:85-97. Close , R. J. Craig, personal observation).

Another Saipan location used for studying flocking behavior extended in a 300 m radius surrounding a single mist-net station, and included ~50% alien thickets of Leucaena leucocephala, Lantana camara, Cocos nucifera, and Carica papaya interspersed with elephant grass (Pennisetum purpureum) and other weed grasses, although copses of native trees (15%), including Casuarina equisetifolia, Ficus tinctoria, F. prolixa, Guamia [= Meiogyne] mariannae, Claoxylon marianum, Premna obtusifolia, Erythrina variegata, and Morinda citrifolia also occurred. The remainder of the area consisted of residential development, which birds also frequented, and an unvegetated quarry (52 Craig, R. J. (2002). Aspects of flocking behavior in an endemic Pacific island white-eye. Journal of Field Ornithology 73(1):70–73. Close ).

On Aguiguan, population surveys and behavioral studies of birds were conducted in steep limestone escarp­ments which, unlike level areas, were still vegetated by native forest dominated by such species as Pisonia grand­is, Cynometr­a ramiflor­a, and Guamia [= Meiogyne] marian­nae. Unlike on Saipan, the forest underst­ory was open due to intensive brows­ing by feral goats (Capra hircus). Birds also were mist-netted and banded in alien thickets principally comprised of Lantana camara that were present on level areas formerly cultivated for sugarcane (53 Craig, R. J., R. Kaipat, B. A. Lussier and H. Sabino. (1993). Foraging differences between small passerines on Aguiguan and Saipan. Proceedings, Marianas Research Symposium 1:16−22. Close , R. J. Craig, personal observation).