How Do Seabirds Drink Salt Water?

For people, ingesting salt water is way from refreshing. For those who’ve ever taken a dip within the ocean, you’ve most likely gotten an unintended 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 take in surplus salt from the bloodstream through a community of capillaries and discharge it by way of ducts operating down the beak and brow. The salt, together with every other extra minerals resembling potassium and calcium, then drips out of the chook’s nostrils as a goopy brine.  

For many animals, shortly consuming plenty of salt triggers a situation referred to as hypernatremia: The physique retains an excessive amount of water in an effort to dilute the sodium, inflicting bloating and hypertension. Some marine mammals resembling 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 hold themselves wholesome and hydrated whereas deliberately ingesting salt water, because of their particular glands.

Scientists had 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 had been beforehand thought of deadly. The birds in his research later had what regarded like runny noses, shaking their heads as they discharged a substance with a salt focus considerably larger 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 way 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 operate greater than others, says Don Lyons, director of conservation science at Audubon’s Seabird Institute. Some, resembling pelicans and gulls, seem to drink salt water solely when it’s their best possibility. 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 food regimen.  “It’s probably not clear how a lot a few of these hardcore seabirds that spend a lot of the yr within the ocean really have to drink,” Lyons says. “Their meals naturally comprises an uncommon quantity of water, so we’re nonetheless attempting 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 offer some species a powerful tolerance for salt. For species that always reside and hunt alongside coastlines, like Mallards and Pink-tailed Hawks, the glands probably permit 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 normally 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 completed 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 a number of the solely water accessible is tremendous salty,” she says. “We anticipate that birds on the market are going to have to start out relying extra on saltier sources 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, finally depends on human efforts to curb fossil gas emissions and preserve and restore habitats. 

Nonetheless, researchers say learning seabirds’ feats of water resilience might assist to make clear the way to assist populations rebound and endure. “They’re superb athletes,” Lyons says, “and we nonetheless have loads to study.”