Us­ing Their Senses

Learn how birds rely on sight, smell, sound, touch and taste to sur­vive.

Birds & Blooms - - Contents - Kenn and Kimberly Kauf­man en­joy the sights and sounds of wild birds near their home in Ohio, but they gen­er­ally don’t try to de­tect them by any other senses.

INCHES, SPAR­ROWS AND CAR­DI­NALS are hap­pily fill­ing up at your back­yard feed­ers. All of a sud­den, they quickly fly away, div­ing into the bushes. Less than a minute later, a hawk swoops through the yard. How did the songbirds know the hawk was com­ing? Did they smell, or maybe hear, it? To fig­ure this out, it helps to know more about the senses that birds use to ex­pe­ri­ence the world around them.

Bird’s-eye View

The term “ea­gle-eyed” for sharp vi­sion is no ac­ci­dent. Nearly all birds see at least two or three times as much de­tail as hu­mans, mak­ing them able to spot food— or ap­proach­ing preda­tors—that much far­ther away. Most birds have ex­cel­lent color vi­sion, too. Night birds like owls may have a bi­o­log­i­cal trade-off: They see very well in dim light, but their per­cep­tion of col­ors may not be as good.

An­other ad­van­tage birds have is see­ing ul­tra­vi­o­let light. To hu­mans, male and fe­male north­ern mock­ing­birds look ex­actly the same—but birds are able to tell the dif­fer­ence be­cause the two have dif­fer­ent ul­tra­vi­o­let mark­ings.

Be­cause their eyes are on the sides of their heads, most birds take in two sep­a­rate pic­tures of their world, one on each side, with only a lim­ited area of twoeyed vi­sion to­ward the front. That means while they see lots of de­tail, it is harder for them to judge dis­tance on the sides un­til they move their heads.

And birds’ eyes process in­for­ma­tion much faster than hu­man eyes. When you watch a film, the pro­jec­tor may show 24 frames ev­ery sec­ond, but your eyes blend them to­gether so you see smooth, con­tin­u­ous mo­tion on the screen. For a bird, the same film would look like a quick se­ries of sep­a­rate pic­tures. This rapid vis­ual judg­ment is very help­ful for a bird zoom­ing among tree branches, for ex­am­ple.

This long-eared owl is named for the tufts on its head. They look like ears, but they’re just feath­ers, and they may help to cam­ou­flage the owl by break­ing up its out­line.

Hear This

They’re not vis­i­ble, but birds do have ears on the sides of their heads. The open­ings are lo­cated below and be­hind the eyes, hid­den by feath­ers.

Hear­ing is crit­i­cal to bird sur­vival. They need acute hear­ing to com­mu­ni­cate, rec­og­nize their young in large nest­ing colonies, and lis­ten for preda­tors and some­times prey. Owls have spe­cial adap­ta­tions for the lat­ter task—ears that are sit­u­ated asym­met­ri­cally, with one slightly lower than the other. This helps them to de­tect more pre­cisely where a sound is com­ing from, so they can hunt suc­cess­fully even in com­plete dark­ness of night.

While the tufts of some owls may look like ears, they’re re­ally just feath­ers. Even the shape of feath­ers on faces helps with hear­ing, with fa­cial discs that fun­nel sound back to their ears.

Birds’ ears, just like their eyes, take in in­for­ma­tion very quickly. If you record a sim­ple bird­call and slow it down, you will dis­cover all kinds of de­tails there that your ears didn’t hear. Other birds prob­a­bly can hear these ex­tra sounds—oth­er­wise there would be no rea­son for the birds to make them.

Touch and Go

Birds use their sense of touch in a va­ri­ety of ways, in­clud­ing feed­ing and fly­ing. They have highly sen­si­tive touch re­cep­tors in ar­eas such as their feet, bills and tongues. Some shore­birds feed al­most ex­clu­sively by touch. As they probe the mud, con­cen­trated touch re­cep­tors in bills al­low them to de­tect and gob­ble up prey items hid­den below the sur­face.

Wood­peck­ers use sen­sors in their tongues to de­tect grubs and other food items. Birds also use touch to sense slight changes in air pres­sure, ad­just­ing their wings ac­cord­ingly. There are ac­tu­ally no nerve end­ings in the feath­ers them­selves, but there are sen­si­tive nerves where the feath­ers grow from the skin.

A Sixth Sense

In ad­di­tion to their five senses, birds have one other amaz­ing abil­ity—they sense the Earth’s mag­netic field. This abil­ity to judge north and south is clearly help­ful as they nav­i­gate the sky, es­pe­cially in mi­gra­tion sea­sons. Sci­en­tists are still fig­ur­ing out how they do it, but the lat­est clues sug­gest that mag­netic de­tec­tion is based in cer­tain pro­teins in their eyes. In a way, birds may be “see­ing” the mag­netic field.

A Mat­ter of Taste (and Smell)

Birds have far fewer taste buds than hu­mans do, so their sense of taste may not be as well de­vel­oped, but no one knows for sure. Sci­en­tists have learned that hum­ming­birds can judge how much sweet­ness is in nec­tar or su­gar wa­ter. And most birds quickly spit out cater­pil­lars that con­tain bit­ter chem­i­cals.

Peo­ple used to be­lieve that birds had very lit­tle sense of smell, but ad­vanced re­search is chang­ing that idea. For ex­am­ple, turkey vul­tures find car­rion by smell, and seabirds that wan­der the ocean catch a faint whiff of food from far away. In fact, many birds may be able to de­tect some scents. But it’s prob­a­ble that on av­er­age, their sense of smell isn’t much bet­ter than a hu­man’s.

Over­all, birds ex­pe­ri­ence their world in many of the same ways that we do, with a fo­cus on sight and sound—but with some fas­ci­nat­ing dif­fer­ences, too.

Prairie war­bler

BY KENN AND KIMBERLY KAUF­MAN

Great horned owl

Male and fe­male mock­ing­birds look the same to hu­mans, but height­ened vi­sion lets birds see the dif­fer­ences.

At feed­ing time, a Wil­son’s snipe uti­lizes touch re­cep­tors in its long bill to lo­cate worms and other in­ver­te­brates un­der­ground.

Turkey vul­tures use their sense of smell to lo­cate car­rion, the most im­por­tant part of their diet.

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