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Altitudinal Variations in Nests of the Hawaiian Honeycreeper Hemignathus virens virens

Michael D. Kern and Charles Van Riper III
The Condor
Vol. 86, No. 4 (Nov., 1984), pp. 443-454
DOI: 10.2307/1366825
Stable URL: http://www.jstor.org/stable/1366825
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Altitudinal Variations in Nests of the Hawaiian Honeycreeper Hemignathus virens virens
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Abstract

We examined more than 90 nests of the Common Amakihi (Hemignathus virens virens) from the Island of Hawaii to determine if their placement, composition, or insulation varied with meteorological conditions at the time of nesting. Common Amakihi nest chiefly during the wet season. The nests were always within the canopy of the nest trees and consequently were probably shielded from rain. The nests from a warm rain forest on Kohala Mountain were significantly higher in the canopy and nearer each tree's center than the nests from Mauna Kea, a cold upland savannah. On Mauna Kea, nests were nearer the edge of the canopy at higher elevations, i.e., in a location where they would benefit from radiant solar energy. Nests from Kohala Mountain lacked liners and were more porous than those from Mauna Kea. These features permitted the nests to dry rapidly. Nests from Mauna Kea, in contrast, were always lined, which retarded drying and increased their insulating capacity--features appropriate for the drier, colder conditions in areas where they were built. All of the nests were excellent windscreens. The thermal conductance of nests from Mauna Kea diminished with altitude, i.e., nests at higher elevations had more insulation than those at lower elevations. This trend was associated with differences in the nests' walls, which were denser (but not thicker) at higher elevations. The nest's thermal conductance can be used to estimate the energetic expense of incubation. For Common Amakihi, the energy required to keep a clutch at incubation temperature may be as much as 0.115 W or 47% of the birds' metabolic rate at rest.

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