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Water Vapor Conductance in Gray Gulls (Larus modestus) Eggs: Adaptation to Desert Nesting

Carlos G. Guerra, Roberto E. Aguilar and Lloyd C. Fitzpatrick
Colonial Waterbirds
Vol. 11, No. 1 (1988), pp. 107-109
Published by: Waterbird Society
DOI: 10.2307/1521176
Stable URL: http://www.jstor.org/stable/1521176
Page Count: 3
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Water Vapor Conductance in Gray Gulls (Larus modestus) Eggs: Adaptation to Desert Nesting
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Abstract

Eggs of Gray Gulls (Larus modestus) which nests in the Atacama Desert of northern Chile, exhibit lower water vapor conductance (G-H20) than predicted by general equations for birds. Their G-H20 (3.70 mg day-1 torr-1) is 33 percent of that predicted by a model for seagulls. Compared to eggs of the desert-nesting Heermann's gull (L. heermanni), Gray Gull eggs lose water one-third as fast. Low G-H20 is a unique adaptation to nesting in the interior of the Atacama Desert, 35-100 km from water. As a consequence of the adaptation of reduced functional pore area of the shell, which is implied by low G-H20, Gray Gulls have a protracted incubation period compared to semiprecocial species with similar sized eggs. /// Los huevos de garuma Larus modestus, que nidifica en el desierto de Atacama, muestran una conductancia de vapor (G-H20) mas baja que la obtenida mediante ecuaciones generales para aves. El valor de G-H20 de los huevos (3.70 mg day-1 torr-1) es 33% de aquel obtenido del modelo para gaviotas. Comparados con los huevos de Heermann's gull L. heermanni, que también nidifica en ambientes desérticos, los huevos de garuma pierden agua a un tercio de su tasa. La baja conductancia, es una singular adaptación para la nidificación en el desierto de Atacama, a 35-100 km del agua. Como una consecuencia de la adaptacion del area funcional de poros, manifestada por la baja conductancia, las garumas tienen un perido de incubacion mas largo, comparado con especies semiprecociales y con huevos de tamaño similar.

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