Chris Packham, in BBC’s Springwatch Guide to Sea Birds, discussed the tubular extensions to the nostrils of petrels (Procellariiformes). He repeated the common explanation that they serve to remove secretion from the salt glands, adding that otherwise the salt solution would fall on the feathers. They certainly do act as conduits for salt-gland secretion. Shortly after Knut Schmidt-Nielsen discovered salt glands, he wrote an article in 1959 for Scientific American illustrated by a photograph showing salt gland secretion being blown from the tubular nostrils of a petrel.
Continuous flight may hamper the flow of fluid from the nostrils because of the current of air over this region and the tubular extensions through which the fluid can be blown by a forced expiration could well act in the way Schmidt-Nielsen suggested.
|You can see the tubular extensions in this young Murphy's Petrel|
(Pterodroma ultima). I photographed this chick on Ducie Atoll in the
Pitcairn Islands on 24 October 2010