Author(s): Woodin, M. C., Michot, T. C. & Lee, M. C.
Title: Salt gland development in migratory redheads (Aythya americana) in saline environments on the winter range, Gulf of Mexico, USA
Year: 2008
Volume: 54
Pages: 251-264.
Abstract: Redheads (Aythya americana) migrate annually from their breeding range in the interior of North America to winter along the coasts of the United States and Mexico. Two of the most important areas where redheads traditionally concentrate in winter are the Laguna Madre and nearby bays in southern Texas and the Chandeleur Sound in southeastern Louisiana. Redheads experience saline-to-hypersaline (less than 35 ppt) conditions in southern Texas, where they have ready access to numerous coastal ponds for drinking water. Redheads in the Chandeleur Sound experience reduced salinity (less than 30 ppt), and they seldom use supplemental fresh water. We weighed and analyzed supraorbital salt glands from redheads wintering in Texas and Louisiana. Mean mass of salt glands was lowest in November and became stabilized in size by January. Mean mass of salt glands in Texas did not differ between the two winters. The mass of salt glands of redheads from Texas (winters combined) was intermediate to, and significantly different from, the mean masses of salt glands of redheads from two different winters in Louisiana. Females exhibited smaller salt glands than did males in both Texas and Louisiana, suggesting that they were under less osmotic loading than males. Young birds during the second winter in Louisiana exhibited the heaviest salt glands, and therefore the most osmotic loading, of all birds in both states. Water balance concerns and osmoregulatory costs should be integrated more fully into future foraging and energetics studies of water birds in marine, coastal, and estuarine systems.
Keywords: salinity, Aythya americana, Louisiana, redhead, salt gland, Texas
Journal: Acta Zoologica Academiae Scientiarum Hungaricae
Journal abbreviation:
ISSN: 1217-8837
Publisher: Hungarian Natural History Museum, Budapest
Editor(s): Bakonyi, G., Mahunka, S., Papp, L., Báldi, A., Csuzdi, Cs., Forró, L., Andrikovics, S. & Kerekes, J.
