"Long before it's in the papers"
January 27, 2015


Hummingbird’s hover surprisingly easy to “hack”

Dec. 10, 2014
Courtesy of the University of British Columbia
and World Science staff

Hum­ming­birds’ re­mark­a­ble abil­ity to hov­er in place de­pends on a mo­tion­less field of view pre­sent­ing itself to the ti­ny, nectar-feed­ing birds, ac­cord­ing to new re­search.

Univers­ity of Brit­ish Co­lum­bia zo­ol­o­gists Ben­ja­min Goller and Doug­las Alt­shuler stud­ied how the sur­pris­ingly in­tel­li­gent bird­s—their pea-sized brains are very large for their body size—stay place while hov­ering.

A flying Anna's hum­ming­bird dur­ing a pre­lim­in­ary ex­peri­ment. (Pho­to: © Matt­hew Shain 2014)

The re­search­ers pro­jected mov­ing spir­al and striped pat­terns in front of free-flying hum­ming­birds try­ing to feed from a sta­t­ionary feed­er. Even min­i­mal back­ground pat­tern mo­tion caused the hum­ming­birds to drift, ac­cord­ing to the find­ings, pub­lished in the jour­nal Pro­ceed­ings of the Na­t­ional Acad­e­my of Sci­ences.

Giv­ing the birds time to get used to the situa­t­ion did­n’t help them, the sci­en­tists found. Pro­ject­ing a com­bina­t­ion of mov­ing and sta­t­ionary pat­terns in front of the birds did­n’t do much good ei­ther, though the birds were able to re­gain some sta­bil­ity.

Pho­tos and vi­deo of the hum­ming­bird ex­pe­ri­ment are availa­ble here.

“We were very sur­prised to see how strong and last­ing the dis­rup­tion was—birds with hov­ering and feed­ing abil­i­ties fine-tuned to the mil­li­me­ter were off the mark by a cen­time­ter,” ten times as much, said Goller. “We think the hum­ming­bird’s brain is so pre­cisely wired to pro­cess move­ment in its field of vi­sion that it gets over­whelmed by even small stim­u­li dur­ing hov­ering.”

“Our brains in­ter­pret vis­u­al mo­tion based on our cur­rent cir­cum­stances,” added Alt­shuler. “We re­act very dif­fer­ently to side­ways move­ment in a parked car than while driv­ing. Now we want to in­ves­t­i­gate how birds use vi­sion dur­ing tran­si­tions from mode to mode, for ex­am­ple as they move from hov­ering to for­ward flight.”

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Hummingbirds’ remarkable ability to hover in place depends strongly on having a motionless field of view before the tiny, nectar-feeding birds, according to new research. University of British Columbia zoologists Benjamin Goller and Douglas Altshuler studied how the surprisingly intelligent birds—their pea-sized brains are very large for their body size—stay place while hovering. The researchers projected moving spiral and striped patterns in front of free-flying hummingbirds trying to feed from a stationary feeder. Even minimal background pattern motion caused the hummingbirds to drift, according to the findings, published in the journal Proceedings of the National Academy of Sciences Giving the birds time to get used to the situation didn’t help them, the scientists found. Projecting a combination of moving and stationary patterns in front of the birds didn’t do much good either, though the birds were able to regain some stability. Photos and video of the hummingbird experiment are available here. “We were very surprised to see how strong and lasting the disruption was—birds with hovering and feeding abilities fine-tuned to the millimeter were off the mark by a centimeter,” ten times as much, said Goller. “We think the hummingbird’s brain is so precisely wired to process movement in its field of vision that it gets overwhelmed by even small stimuli during hovering.” “Our brains interpret visual motion based on our current circumstances,” added Altshuler. “We react very differently to sideways movement in a parked car than while driving. Now we want to investigate how birds use vision during transitions from mode to mode, for example as they move from hovering to forward flight.”