University of Alberta researchers have pinpointed a section in the tiny hummingbird's brain that may be responsible for its unique ability to stay stationary mid-air and hover.
"This was a very exciting moment for us," said Dr. Doug Wong-Wylie, Canada Research Chair in Behavioural and Systems Neuroscience and psychology professor at the U of A. "As soon as we looked at these specimens it was obvious that something was different in the hummingbirds' brains than other species."
Wong-Wylie and Dr. Andrew Iwaniuk, also from the Department of Psychology in the Faculty of Science, compared hummingbird brains to 28 other bird species, obtained from the National Museum of Natural History, the Field Museum of Natural History, and the Louisiana State University Museum of Natural Science. Hummingbirds are well known for their wing speed and ability to hover and fly forward and backward with more precision than a helicopter. It is critical that the hummingbird remain perfectly still as it feeds itself while darting in and out of flower blossoms with pinpoint accuracy. The bird must be able to maintain a stable position space, despite the fact that their wings are beating 75 times per second and that disruptive effects such as wind gusts could throw them off.
Much work has been done on the hummingbirds' physiological make up--such as its enlarged heart, high metabolic rate and specialized wing kinematics--but nothing has been done on the neural specializations of the bird.
"Part of the reason this type of work hasn't been done before is because of access to the birds," said Iwaniuk. "In Canada especially they tend to be uncommon, they come from exotic locales and they are not easy to catch, so we were very fortunate to be able to study the specimens we did."
The scientists found that a specific nuclei--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. The hummingbird's brain is smaller than a fingertip. "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 per cent of the time. This specific nuclei is likely responsible for that."
Wong-Wylie and Iwaniuk plan to continue this line of research and have hummingbirds track visual motion while watching the nucleus to see how it reacts.
This research is published early online in "The Journal of Comparative Neurology" and will come out in its print edition in January.
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