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Laysan Finch Nest Characteristics, Nest Spacing and Reproductive Success in Two Vegetation Types
Marie P. Morin
Vol. 94, No. 2 (May, 1992), pp. 344-357
Published by: American Ornithological Society
Stable URL: http://www.jstor.org/stable/1369207
Page Count: 14
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The typical Laysan Finch (Telespiza cantans) nest on Laysan Island is composed primarily of the bunchgrass Eragrostis variabilis, and is hidden from view within a bunchgrass clump. About one-third of the nests have two or more plants species in the nest substrate and canopy. Nests are usually in the lower two-thirds of the bunchgrass clump, and in the lee of the prevailing winds. The dimensions of nests and nest substrates were compared between the predominant vegetation associations: bunchgrass and viney. Almost all nests occurred in these two associations. Nests in the bunchgrass association had more of their canopies composed of a single plant species, had substrates with greater maximum heights, had more cover over the nest cups, and had wider outer nest diameters. Nine other nest and nest substrate variables showed no difference between the two vegetation types, nor did clutch size and fledging success differ significantly, although evidence suggested that fledging success may differ for early (or late) season nesters. Nearest-neighbor distances of simultaneously active nests were larger in the bunchgrass association than in the viney, and nest densities were approximately half. Nests were relatively more aggregated in the viney association. The viney association occupies half as much total area as the bunchgrass association, but it appears to be the most productive per unit area for nesting. The rapid invasion over the past 29 years by a non-native bush (Pluchea indica) into this important vegetation association warrants further study into the possibility of vegetation control.
The Condor © 1992 Cooper Ornithological Society