Bird barometer

I can usually tell what sort of weather conditions are coming using my “bird barometer”, which consists primarily of monitoring the intensity with which birds are feeding at the various feeders scattered around the backyard.  About 24 hours before a big thunderstorm or a dreary day with steady rainfall, those feeders are humming with activities of multiple individuals of a variety of species.  For example, yesterday was cloudy but mild, but dozens of finches, sparrows, and chickadees crowded in or around the feeders for several hours in the morning.

white-throated-sparrow-

A flock of a dozen or so White-throated Sparrows searched through the grass and leaves beneath the feeders, often chasing each other away from hot spots where the seed had dropped from the feeders above.

slate-colored-junco-

Mixed in with the Sparrows were a bunch of Juncos, equally intolerant of others foraging near them. Extended chases of a bird that encroached on another’s foraging space was common.

fox-sparrow-

A newcomer to the backyard showed up — a Fox Sparrow.  I’ve seen these birds only rarely, and usually just a brief glimpse as they migrate through MN on their way to their breeding grounds in Alaska or their wintering grounds in the southeastern U.S.  They scratch through the litter beneath dense cover, making them tough to spot.

fox-sparrow-

Fox Sparrows are larger than most other sparrows, with bold breast stripes, a gray stripe above the eye, and rusty red tails and backs. The western US subspecies are slate gray though.

These ground-feeding birds were reaping the benefits of all the spilled seed from the multiple gangs of finches, chickadees and nuthatches vigorously attacking the feeder above them.

house-finch-and-goldfinch

Red splashes of color on the male House Finch and yellow splashes of color on the heads of the Goldfinches — the last remnants of their colorful selves from the past breeding season.

purple-finches-and-house-finch

Purple Finches (male on lower right, female on lower left) dominate the feeder to the exclusion of the slightly smaller Goldfinches and Chickadees.

Today (just 24 hours after the feeding frenzy) is rainy and cold, and the feeders are quiet.  An occasional Blue Jay visits, but even the Chickadees are absent.  How do birds predict such changes in the weather?  Do they really have an internal barometer?

In fact, they do.  A group of hair cells in the Vitali Organ, or Paratympanic Organ (named for Giovanni Vitali who discovered them about 100 years ago) in the middle ears of birds is thought to be responsible for detecting changes in atmospheric pressure of just 10-20 mm of water (about 0.75-1.5 mm of mercury).  Such exquisite sensitivity allows birds to maintain their elevation while flying long distances within 10-20 feet of desired altitude — essential for navigation, but it also allows birds to sense changes in barometric pressure at ground level, especially the declining barometric pressures that signal approaching storm fronts.  Input from these specialized cells due to barometric pressure changes then causes abrupt and marked changes in bird behavior, as they prepare for and protect themselves from changes in the weather.

Are birds the only animals with this unique ability?  Hardly.  Most animals can sense impending changes in the weather, using a variety of other cues (infrasound, daylight, smell (ozone?), static electricity, etc.).  But only one group of mammals may possess the type of middle ear barometric pressure detectors present in birds.  Can you guess what group that might be?

An interesting reference on this subject can be found here:  Von Bertheld and Gianessi, 2011. The Paratympanic Organ:  A barometer and altimeter in the middle ear of birds? Journal of Experimental Zoology 316 (6): 402-408.

12 thoughts on “Bird barometer

  1. I am fairly new to your blog, and I really enjoy it. The pictures are great! I did not know the fox sparrow at all. Thanks for doing this!

  2. I’ve been noticing bird activity picking up at my feeders too. Juncos showed up today for the first time so I know the cold is soon here to stay. White-throats are here already and I usually see a fox sparrow or two on their way south.

    • I should have noted that Juncos do seem to arrive just as the temperatures drop, but we seem to be having a extra week of above normal temps here this year.

  3. Very interesting, I don’t think I would have guessed bats but perhaps they have gone their own way with their senses in other ways. I must check out if I can use our birds to predict the weather but ours just seem always hungry 😦 Amelia

    • YOU GOT IT! I was disappointed more people didn’t try to guess, but you’re absolutely right on. What’s strange is that other mammals don’t seem to have these cells at all. I’m not sure they have looked in whale or dolphin ears though.

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