December 13, 2009

Bird sounds

Remember Dolphins Evolve Opposable Thumbs? One of the finest things the Onion has ever produced, if you ask me. Turns out Aves may be another group to keep an eye on.

If you watched the terrific video on parrot intelligence [H/T Heckled by Parrots, via Pet Connection], you probably caught a glimpse of a scientist in a lab. He was on screen for just a few seconds, at 5:44 in the vid. That's Erich Jarvis. Here's his Duke U. faculty page. From the NOVA site:
Erich Jarvis is a neurobiologist at Duke University Medical Center. He heads a team of researchers in the field of vocal communication. The Jarvis Lab's research of songbirds, parrots, and hummingbirds sheds light on how the brain is able to learn the behavior of sound. Jarvis's work on bird brains may have applications to the treatment speech problems in humans, such as stuttering. In October 2005, Dr. Jarvis won the National Institutes of Health's Director's Pioneer Award, which provides $500,000 per year for five years to researchers pursuing innovative approaches to biomedical research.

This summer Jarvis gave the keynote address at the annual meeting of the American Ornithologists' Union:
Vocal learners mimic sounds they hear, and then modify them to create new sounds. This may not be as much mindless parroting as we used to think—and here Jarvis singled out Irene Pepperberg in the audience, whose experiments with Alex the African Grey Parrot showed that he understood the semantics of a question like “How many total?” well enough to count and reciprocally communicate to Irene that two beads and four beads made “six.”

As for how vocal learning happens, Jarvis and colleagues reported in a staggering series of publications that while all birds use parts of the brain stem to produce songs, those with learned songs also use parts of the forebrain. Birds that learn their songs may even have more than one pathway controlling their learning. One pathway may promote variability in songs while another pathway produces more consistency, or stereotyping. The proper balance between the two pathways allows for vocal learning.
Jarvis basically threw out the window the received wisdom that humans’ large brain size and extensive brain folding are the explanation for our complex language. When he and colleagues described in 2005 how bird song and human speech actually make use of the same three forebrain regions, it made a splash. People reportedly called Webster’s and asked them to remove the term “bird brain” from the dictionary. [Source: Round Robin — The Cornell Blog of Ornithology.]

You can read more about the evolution of avian brain structure for vocal learning here, at the Jarvis Lab website.


Also on the topic of bird communication: in a thoughtful [as in, both gracious and brainy] exchange of blog posts, David Sibley and Nathan Pieplow engage in a "very interesting and, I think, important discussion about a sea change that may be occurring in how birders listen to bird sounds." [That quote is from Pieplow's blog.] Sibley writes:
I learned bird songs decades ago through countless hours of field experience, supplemented by listening to a few recordings, reading detailed descriptions, and talking to other birders. It was a subjective, holistic approach to bird songs that led to a sort of gestalt style of identification – after you hear a sound often enough the identification just becomes second-nature.

Now, it still takes countless hours, but birders have a wealth of technological aids, allowing them to study and compare bird sounds with an ease and immediacy that was never possible before. In the modern world of ipods, sonagrams, and websites like xeno-canto, birders can examine the bird sounds directly, objectively, and in great detail. This may lead (as Nathan Pieplow admits) to a slightly greater emphasis on differences in pattern rather than the more subjective and hard-to-describe differences in tone.

Given how suggestible we are, and how tiny things can influence our perception, the detail-oriented objective approach to bird sound identification is probably better and more accurate.

And Pieplow replies:
[Sibley] learned sounds in the field; I learned them on the floor of my bedroom in South Dakota when I was in high school, playing the Peterson Birding By Ear tapes over and over again. Those tapes (which remain the best resource I’ve ever seen for people who want to learn bird sounds on their own) didn’t take a holistic, all-at-once approach; instead they took an analytic approach, grouping similar sounds together and then pointing out key field marks or “handles” — here a distinctive tone quality, there a distinctive rhythm — to distinguish sounds within the groups.

I’ve used this same basic approach to sound identification ever since: recognize a pattern, then focus on a piece of it. The pattern gets you to the right group; the pieces narrow the identification to species. Tone quality is part of this analysis, but not the most important part.

In fact, in some ways I think I place a pretty low priority on tone quality. For several years now, I have been convinced that tone quality is the slipperiest attribute of sound: the hardest to analyze perceptually, the hardest to describe. And I think tone quality is responsible for most of the disconnect between most descriptions of sounds and the sounds themselves. I de-emphasize it precisely because it is so difficult to categorize. Other attributes of sound are much easier to describe and compare, so those are the ones I focus on.

For the most part, I’m just doing what works for me, but I hope it works for other people as well. I really do believe in the objective, analytic approach.


So who makes those field recordings of bird songs? Remarkable people like William Belton:
An internationally recognized ornithologist, Mr. Belton was almost single-handedly responsible for the current body of knowledge of the bird life of Rio Grande do Sul, the southernmost Brazilian state. His field recordings and specimens from the region are today in the collections of major research institutions. His two-volume study of the birds of the area is widely considered seminal.
Each [of Belton's recordings] was often the product of hours of standing stock-still in the wild at dawn, with swarms of biting insects for company. But the rewards were considerable: over the years, Mr. Belton captured many bird songs that had never before been documented.
The bird names alone read like found poetry. Mr. Belton recorded, among others, the variable screech-owl and the southern screamer; the freckle-breasted thornbird, the sooty-fronted spinetail and the rufous-browed peppershrike; the cattle tyrant, the masked yellowthroat and the piratic flycatcher; the squirrel cuckoo, the laughing falcon, the pectoral sandpiper and the gilded sapphire.

William Belton died in October at the age of 95. As a woman of a certain age, I love that Mr. Belton's ornithological career [of more than 30 years!] began following his retirement.


A high school student asks Erich Jarvis, "African grey parrots can learn to speak, and they can be taught to tell color, and even to express themselves. And from what I observed on NOVA scienceNOW, some birds are capable of creating simple tools. But what about the other kinds of birds that are incapable of doing things like this? For example, a crow can make tools to obtain food but a pigeon can't. Why? Why is the parrot smarter than the finch? Is it brain size, the way they use their brains, or does the parrot have something the finch doesn't?"

An excerpt from Jarvis's answer:
[A]n argument can be made that having a brain means that you have intelligent behavior, regardless of whether you are a bird, mammal, reptile, or otherwise. But this is not the way many people think. There is something inherent in our human psyche that wants to make nonhumans "lower" in intelligence, and for us to form a scale of intelligence such that some species would be considered not intelligent.
In fact, it is very difficult or almost impossible to make such a scale. Yes, a crow can make tools, and as far as I know, this has not been observed in pigeons. But pigeons have incredible visual memories and abilities, including the ability to learn how to distinguish different styles of impressionistic paintings. Chickadees, which are a type of songbird, can store over 3,000 seeds in the forest, and during the winter they remember where they put them and retrieve most of them. A parrot so far as I know has not been observed to do this, yet a number of parrot species can imitate some human speech.
Different species have different behavioral capacities that vary in sophistication, Jarvis continues. However, brain size is not the main driving factor behind these complex behaviors. Instead, neural connectivity appears to be the driving force.

And bird brains, as it turns out, are firing on all cylinders.

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