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Osmoregulation
Adélie penguins are faced with extreme osmotic conditions, as their frozen habitats offer little fresh water. Such desert conditions are known to force birds such as Adélie penguins to intake excess electrolytes through their diets[1]. They manage to circumvent this problem by eating krill with internal concentrations of salt at the lower end of their possible concentrations, helping to lower the amount of ingested salts[1]. The salt load imposed by this sort of diet is still relatively heavy, especially when considering the less tolerant chicks. Adult Adélie penguins feed their chicks by regurgitating the predigested krill, which can impose a heavy salt load on the chicks. Adult penguins address this problem by altering ion concentrations while the contents are still in their stomachs. By removing a portion of the sodium and potassium ions, adult Adélie penguins manage to protect their chicks from heavy salt loads[1]. The issues of salt loads is resolved even further by the ability of these penguins to concentrate their excretions to a much higher degree than most other birds. This ability is present regardless of ontogeny in Adélie penguins, meaning that both adults and juveniles are capable of extreme levels of salt ion concentration[1]. However, chicks do possess a greater ability to concentrate chloride ions in their cloacal fluids[1].
Salt glands also play a major role in the secretion of excess salts in Adélie penguins. Due to the relatively inefficient kidneys of aquatic birds, the salt gland takes on most of the responsibility of salt removal. Aquatic birds such as the Adélie penguin have highly developed salt glands which are capable of handling their intense salt loads[2]. As a result, the avian salt gland is capable of excreting fluids even more concentrated than seawater, helping the Adélie penguin to remove large amounts of excess salts through its nares. Specifically, the salt gland works to pump out and concentrate large quantities of sodium chloride.