Allowing the birds their say re:Darwinism

Special Birds with Specialized Abilities

Evolution News & Views July 20, 2015 1:22 PM

Illustra's film Flight: The Genius of Birds showed some amazing specialties in a few bird species: the hummingbird with its nectar-trap tongue, starlings in formation flight, and Arctic terns in long-distance migration. It would take many hours of similar movies, and a book of ENV articles, to even begin to do justice to the many diverse kinds of birds that warrant our admiration. From time to time we can, though, point out particular cases coming to light in new research.

Image Stabilization

Lovebirds; aren't they sweet. We're not talking about newlyweds, but small parrots that inhabit Africa and Madagascar (which do, by the way, show affectionate behavior). A zoologist incorporated the help of mechanical engineers to study something Olympic about them: they can turn their heads "super-fast" in flight. In a paper in PLoS One, the team measured the head turn rate. Although the birds flick their heads back and forth, the rotational motion measured by a high-speed camera is exceptionally fast: 2700 degrees per second.

High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles. In between saccades,gaze orientation is held constant. By comparing saccade and wingbeat phase, we find that these super-fast saccades are coordinated with the downstroke when the lateral visual field is occluded by the wings. Lovebirds thus maximize visual perception by overlying behaviors that impair vision, which helps coordinate maneuvers.... Our observations show that rapidly maneuvering birds use precisely timed stereotypic gaze behaviors consisting of rapid head turns and frontal feature stabilization, which facilitates optical flow based flight control. [Emphasis added.]

The strategy resembles the way early combat aircraft could fire machine-gun rounds without blowing off the propellers. The bird turns the head just in time to minimize the time the wing is in the way of seeing. A summary of the findings tt PhysOrg gives another reason why this research is interesting. "The authors also hope that the accuracy and speed of these visually guided flight-maneuvers may inspire camera rotation design in drones to improve imaging."

Lest you feel any sense of inferiority at this little bird's design, notice what the authors write in the Abstract: "Similar gaze behaviors have been reported for visually navigating humans." This paper in Current Biology about "microsaccades" (tiny eye movements), which unwittingly sample our visual field during focused attention, also bears reading (see the summary atMedical Xpress).

Smell Navigation

Illustra's new film Living Waters points out that the ability to navigate by the sense of smell or by the earth's magnetic field is widespread in many types of animals. Here's a case in point: seabirds. An article at Live Science reports on work by zoologists in the UK who found that "Seabirds smell their way home." Flying over large expanses of open water, birds like Cory's shearwaters manage to find their nesting sites and feeding grounds without error. How do they do it? There aren't many cues available. The authors ruled out some senses, like sound.

Observing how the birds explore an area in detail then move a distance and repeat (a search strategy called a Lévy flight pattern), the researchers found that models based on the sense of smell gave the best fit. It's not easy, though. For smell navigation to work, not only must the sense of smell be incredibly acute, but the birds have to be able to integrate olfactory data with other forces in the environment.

Birds may associate smells, such as those from phytoplankton, with wind directions, the researchers noted. For instance, the seabirds may know to fly westward when they smell one odorand to fly eastward when they smell another. Or, a combination of both smells may prompt them to fly northeast, the researchers said.

However, smells aren't always detectible because of atmospheric turbulence, so birds will reorient and change direction until they find another recognizable smell, the researchers found.

In addition, the birds must have an "odor map" written in the brain that associates the odor cues with memory. In effect, the cues tell the bird, "This combination of odors means you are here, and you need to head that way." As the feeding ground approaches, the birds can rely on additional cues, like "landmarks, flights of other birds and 'colony odors'." Living Waters illustrates a similar capability in fish: a nasal switchboard that guides salmon through a maze of tributaries to its natal stream.

Vocal Imitation

Who hasn't had fun listening to parrots imitate human speech? It takes a special kind of brain to do this. Parrots, parakeets (budgerigars), cockatiels, keas, and our affectionate friends the lovebirds are good at it. Neurologists at Duke University were curious to know what structures in the brain seem to be responsible. They found particular regions they dubbed "shells" around core speech centers that are found in all these species. One researcher's reaction has some bearing on Kuhnian science:

"The first thing that surprised me when Mukta and I were looking at the new results is, 'Wow, how did I miss this all these years? How did everybody else miss this all these years?'" said Jarvis, who is also member of the Duke Institute for Brain Sciences. "The surprise to me was more about human psychology and what we look for and how biased we are in what we look for. Once you see it, it's obvious. I have these brain sections from 15 years ago, and now I can see it."

The news release seems obsessed with how this brain region evolved, stating that whatever mutation led to it happened 29 million years ago, based on assumed evolutionary lineages. That doesn't come close to explaining it:

The new results support the group's hypothesis that in humans and other song-learning animals, the ability to imitate arose by brain pathway duplication. How such a copy-and-paste job could have happened is still unknown.

It's not clear how duplicating a gene or pathway can cause a new complex ability like voice imitation: "It takes significant brain power to process auditory information and produce the movements necessary for mimicking sounds of another species," one of the researchers said. The article does not speculate on what kind of mutational event led to the exceptional abilities of unrelated birds, like the mockingbird or lyrebird.But of what evolutionary survival value is this ability? Clover seems to be enjoying her intricate brain and vocal apparatus. If we don't think human impressionists evolved their repertoire by mistake, perhaps we should give intelligent design, not Darwinian evolution, the credit for bird mimicry and the other exceptional talents