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Index of Subjects I don't know of any bird that is routinely exposed to salt water which doesn't have salt glands in the head (that doesn't mean there aren't any of course). I think even the one of the sparrows (Seaside Sparrow ?) has them. The Marsh Wren has small ones, Clapper/King Rails have them. The depressions in the skull, where these glands sit, are very prominent in loons (both species here have them). I have posted two views of a loon skull at: http://people.stfx.ca/rlauff/343/loonsaltglandfossae.jpg. The arrow shows the gland's location in lateral view, which isn't the best way to see it, the red outline in the dorsal view shows the depression quite well. Although, I'll admit, it's much nicer seeing it in the flesh (so to speak). I believe you're right in that avian kidneys are as efficient as typical mammalian kidneys at least, but I don't think they are the sole salt excreting organ in any seabird. In other words, I've never heard of a bird having as efficient a kidney as a whale or seal, for example. Not my area of expertise really, but I do dabble in physiology now and again. Randy On 10/06/2009, uhoeger@dal.ca <uhoeger@dal.ca> wrote: > I have on answer and one educated guess to offer. > >> Question number one: How do loons excrete saltwater? Is this the same >> process as in other >> seabirds? This is when loons over-winter in our saltwater environment or >> when they spend the >> summer there. They dive and must take in some saltwater in the process of >> catching prey items. >> How is this expelled. > > Some pelagic seabirds have salt glands in their heads that help to regulate > the animals salt balance. All other birds, including loons, have to rely on > their > kidneys to regulate their water and salt balance. Avian kidneys are as > efficient as mammalian kidneys when it comes to the production of highly > concentrated (salty) urine to minimize water loss. > >> >> Question number two: Loons eat a lot of crabs. How is the carapace of the >> crab dealt with in >> respect to digestion? > > I guess the same way as gulls, herons, and many other birds. Material that > is not digestible (and crab shells likely fall in this category) is > regurgitated, > i.e. leaves the body the same way it came in. > > > Hope that helps > > Cheers > > Ulli > _________________________________ RF Lauff Way in the boonies of Antigonish County, NS.
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