How Do Seabirds Drink Salt Water?

For people, ingesting salt water is way from refreshing. In case you’ve ever taken a dip within the ocean, you’ve in all probability gotten an unintentional mouthful and know the nasty, dehydrated feeling that may be relieved solely by a swig of contemporary water. However for a seabird, ingesting sea water isn’t just tolerable—it’s completely hydrating.

The key to this superpower? Seabirds have a pair of salt glands above their eyes that act like an additional, miniature set of kidneys. The glands soak up surplus salt from the bloodstream through a community of capillaries and discharge it by means of ducts operating down the beak and brow. The salt, together with another extra minerals reminiscent of potassium and calcium, then drips out of the hen’s nostrils as a goopy brine.  

For many animals, rapidly consuming loads of salt triggers a situation known as hypernatremia: The physique retains an excessive amount of water in an effort to dilute the sodium, inflicting bloating and hypertension. Some marine mammals reminiscent of seals and dolphins have extra-robust kidneys that assist them course of their sodium-rich seafood, although they don’t swallow ocean water on function. However seabirds can maintain themselves wholesome and hydrated whereas deliberately ingesting salt water, due to their particular glands.

Scientists have been lengthy conscious of those organs however remained mystified by their function till the mid-Twentieth century. However in 1960, Knut Schmidt-Nielsen, a comparative physiologist at Duke College, published a paper that made the connection. For the experiment, Schmidt-Nielsen injected seabirds with volumes of salt water that have been beforehand thought of deadly. The birds in his examine later had what regarded like runny noses, shaking their heads as they discharged a substance with a salt focus considerably greater than that of their urine. One Nice Black-backed Gull even ingested one-tenth of its physique mass in sea water and eradicated the salt by means of its urine and nasal drip after solely three hours. 

All seabirds—birds that spend most of their life in or across the ocean—can desalinate, however some species depend on the perform greater than others, says Don Lyons, director of conservation science at Audubon’s Seabird Institute. Some, reminiscent of pelicans and gulls, seem to drink salt water solely when it’s their best choice. However others, like albatrosses, penguins, and petrels, can keep hydrated solely on salt water, which they both drink straight from the supply or ingest from their fish-fueled weight loss plan.  “It’s probably not clear how a lot a few of these hardcore seabirds that spend a lot of the yr within the ocean truly have to drink,” Lyons says. “Their meals naturally incorporates an uncommon quantity of water, so we’re nonetheless making an attempt to determine how usually sure species actively hunt down water alone.” 

Different terrestrial birds have comparable glands, too, and although they’re a lot smaller than these of seabirds, the organs seem to provide some species a powerful tolerance for salt. For species that always reside and hunt alongside coastlines, like Mallards and Crimson-tailed Hawks, the glands doubtless enable them to deal with particularly salty meals, says Aimee M. Van Tatenhove, a quantitative ecologist on the Cornell Lab of Ornithology. And for ostriches—which aren’t often beach-dwellers, however usually stay in dry environments—researchers suspect that the organs assist them regulate their physique’s salt content material when contemporary water is in brief provide.

This physiological course of is probably going more and more useful for birds as local weather change drives excessive warmth and freshwater shortage, Van Tatenhove says, although little analysis has been accomplished to find out if species have gotten extra depending on salt water. “We’re seeing megadroughts and water consumption by people out within the American West to the purpose the place among the solely water accessible is tremendous salty,” she says. “We anticipate that birds on the market are going to have to begin relying extra on saltier assets except one thing drastically adjustments.”

Salt glands alone are unlikely to make or break seabirds’ survival in the long term, Lyons says. Species are being threatened by habitat loss from urbanization and rising ocean temperatures, and seabird populations all over the world have declined by 70 percent since 1950. Their continued existence, Lyons provides, in the end depends on human efforts to curb fossil gasoline emissions and preserve and restore habitats. 

Nonetheless, researchers say finding out seabirds’ feats of water resilience may assist to make clear the best way to assist populations rebound and endure. “They’re wonderful athletes,” Lyons says, “and we nonetheless have so much to study.”