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Nest Substrate Variation between Native and Introduced Populations of Laysan Finches

Marie P. Morin and Sheila Conant
The Wilson Bulletin
Vol. 102, No. 4 (Dec., 1990), pp. 591-604
Stable URL: http://www.jstor.org/stable/4162932
Page Count: 14
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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.
Nest Substrate Variation between Native and Introduced Populations of Laysan Finches
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Abstract

On Laysan Island, the endangered, endemic Laysan Finch (Telespiza cantans) nests almost exclusively in the native bunchgrass Eragrostis variabilis. Experimental nest boxes provided were never used for nesting. Marine debris was not used as nest substrate on Laysan Island. In contrast, the introduced Laysan Finch populations on four islands at Pearl and Hermes Reef used a wide variety of native and alien plants as nest substrates, as well as various kinds of human-made debris. However, nest boxes provided at Pearl and Hermes Reef were not used as nest substrates by finches. Eragrostis variabilis is uncommon on Pearl and Hermes Reef, except on Seal-Kittery Island, but is common on Laysan where it is the preferred nest substrate. Eragrostis is a dense bunchgrass which probably provides the nest with good protection from sun, rain, wind, disturbance, and predators. On Pearl and Hermes Reef, where Eragrostis variabilis is uncommon, other plants that provide dense cover are used as nest substrates, and human-made debris that provides some cover is also utilized. It is unclear why nest boxes were never used as nest substrates at either site. We suggest that the conservation of Laysan Finches on Laysan Island will require the maintenance of a native ecosystem where Eragrostis variabilis is a major vegetation component. Otherwise, changes in behavior, morphology, and energy expenditure associated with environmental differences are likely to occur, and may have already occurred in the introduced populations on Pearl and Hermes Reef.

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