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The Hummingbird's Hovering Abillity Comes from Its BrainThe visual-motor nucleus is highly enlarged in these birds |
By Stefan Anitei, Science Editor
30th of November 2006, 13:50 GMT
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Hummingbirds are the smallest birds on Earth, some having 4 cm length and weighing 1.8 g.
These birds are specialized nectar eaters and developed the ability to hover in mid-air by rapidly flapping their wings, 15 to 80 times/second, depending on the species size (the smaller, the more flaps), with more precision than a helicopter. Sustained hovering is accompanied by the ability to fly deliberately backwards or vertically, and to maintain position while drinking from flower blossoms.
Scientists at the University of Alberta have discovered a section in the tiny hummingbird's brain that may enable them to act this type of flight. "From a pure science perspective, it's just amazing that they can do
this because they're staying perfectly stationary in space for long periods of time, despite the fact that their wings are beating at like 75 times per second, which really must be jerking them around," said Dr. Doug Wong-Wylie, psychology professor. Wong-Wylie and Dr. Andrew Iwaniuk compared hummingbird brain to that of 28 other bird species. "As soon as we looked at these specimens it was obvious that something was different in the hummingbirds' brains than other species."
The hummingbird must remain perfectly still as it feeds itself while darting in and out of flower blossoms with pinpoint accuracy, despite their staggering wing beat rhythm and disruptive effects such as the wind blowing that could throw them off.
Hummingbirds' physiology and anatomy behind hovering capacity have been investigated, pinpointing an enlarged heart, high metabolic rate and specialized wing kinematics, like its unique bony shoulder blade structure; however, no study has been done on the neural specialization for hovering. The scientists discovered that a specific nucleus-one that detects any movement of the entire visual world-was two to five times bigger in the hummingbird than in any other species, relative to brain size.
"If you want to make sure you stay stationary, you just have to make sure nothing on the retina moves. That's what this nucleus does," said Wong-Wylie, who has been investigating the lentiformis mesencephali nucleus in different species for about 20 years. "We reasoned that this nucleus helps the hummingbird stay stationary in space, even while they're flying," said Wong-Wylie. "These birds must have a good optomotor response considering they are stationary 90 % of the time. This specific nuclei is likely responsible for that."
Wong-Wylie is also interested in the hummingbird's ability to fly backwards. "We're always talking about wanting to design autonomous robots that can do this, that can maintain their stability. Well, they're going to have to look at the hummingbird to design one." The team plans to investigate how the nucleus reacts to visual motion.
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