In the column “Since You Asked” in every issue of BirdWatching, Contributing Editor Julie Craves answers readers’ questions about birds and bird behavior. Here is a question from our June 2015 issue:
I observed a gull drinking from a tide pool. How is it that birds can drink salt water and not get sick? Do they have to filter it out somehow? — Brooke Sponzo, Boston, Massachusetts
Not all birds are able to drink salt water, but species that spend much of their lives seaside (or at sea, like albatrosses and petrels) have special glands that extract salt from their blood. The glands are usually located near the eyes, and the salty concentrate filtered from the blood is excreted into the nasal cavities. This is why we often see marine birds shaking their heads; they are flinging the briny solution from their bills. Other species have slightly different drainage systems, allowing them to sneeze out the brine or expel it from their mouths.
The glands are also found in birds that inhabit arid habitats. They drink very little water, so the glands handle salts that would otherwise need to be flushed out by the kidneys, a task that requires substantial amounts of fresh water.
About Julie Craves
Julie is supervisor of avian research at the Rouge River Bird Observatory at the University of Michigan Dearborn and a research associate at the university’s Environmental Interpretive Center. She writes about her research on the blog Net Results, and she maintains the website Coffee & Conservation, a thorough resource on where coffee comes from and its impact on wild birds.