Where do ravens and other corvids fit in? They apparently come under the passerines, but they weren’t mentioned in the article. They are great mimics, and the story of the ravens around Buckingham Palace is worth telling. The servants have been teaching these birds English words long enough that the young are now taught some of them before they ever see a human. In a loose sense, things like “Pretty bird!” have become natural calls of this tribe of avians.
Bernd Heinrich’s Mind of the Raven (HarperCollins, 1999) contains some charming accounts of mimicry by both captive and wild ravens. My favorite is the testimony of a Washington park ranger who heard ravens distinctly saying, “Three, two, one, bccccchhh”. The birds were imitating the Avalanche Patrol blowing up snowpacks.
I think the term “characteristic vocalization” ranks up there with “nucleation site”. Plus, I think it could have wide applicability in Great Debates.
“When asked about the effects of the 600 billion dollar package on the budget deficit, Ari Fleisher offered his Republican characteristic vocalization: the deficits are the fault of the weak economy and the stimulus package is designed to address that.”
I’ll leave it to others to present the appropriate characteristic vocalizations for Democrats, fundis, environmentalists, free-traders, etc.
I’m pretty sure there is a lot of variation within passerines as to how much they incorporate mimicry into their vocalizations. Corvids are right up there, but so are birds in the thrasher family. In fact, thrashers & mockingbirds are known for the way they mimic other bird vocalizations, but I don’t think I’ve ever heard of one mimicking human speech. I wonder why that is?
probably if you hand raised a crow or raven, you might get one talking human. It is exposure to sound, and not many people like ravens and crows to expose them to human voices. In my whole life I’ve only met one mynah bird that could speak human, it also imitated a common noisy bird called a koel. There are plenty of mynah birds where I live, but they don’t speak. You have to hand raise birds to speak. Wild cockatoos don’t speak human either, but they are an appealing bird, so get hand raised, and thus speak human.
Colibri’s column omitted the most obvious reason that some birds mimics the songs of other birds:
Birds sing to establish territory - the song is a warning to other birds of the same species to stay away. A song mimic tells birds of all other species to stay away. If it is successful, the mimic doesn’t have to share the food in its territory with any other birds.
Hunh? Birds sing (mostly) to advertise their possession of a territory and attract mates. This doesn’t explain why they mimic - that is, imitate other bird species, or other sounds. In any case, the next-to-last paragraph in my column was about why birds might employ mimicry in territorial advertisement, although I did not specifically use the word “territory” since I thought it was implied.
To answer the OP, yes, corvids (crows, ravens, rooks, jackdaws, jays etc.) are passerines and good mimics, and can be taught to imitate human speech. I even found one reference to a Blue Jay that had been taught to “speak,” but only one word.
I didn’t go into this in the article, but not all birds that mimic can be taught to imitate humans. For example, although the mockingbird is an excellent mimic, I’ve never heard of one being taught to speak in the manner of a mynah or parrot.
While this is just speculation on my part, the tendency to “talk,” that is, imitate the human voice, may be limited to species where an important function of the mimicry is social cohesion through imitation of mates or flock members, rather than territorial advertisement. “Talking” birds - parrots, mynahs, corvids, starlings - seem to be mostly those in which the flock is an important social unit for at least part of the year. These birds imitate their human owners/trainers because they regard them as part of the flock, or possibly a mate. More solitary, territorial species - mockingbirds, thrashers, thrushes, lyrebirds - don’t imitate humans.
SD Staff George (Colibri)
SD Science Advisory Board
As I said, mimicking other birds’ songs tells them to stay away. If successful, it secures everything in the territory to the mimic, including the food.
Jeff, I’m afraid you are missing the point here. A large majority of bird species advertise the possession of a territory by singing [und]only[/und] songs characteristic of their own species. They do not mimic the songs of other species. You are not offering any explanation of why birds should mimic other species, as opposed to singing only their own species-specific songs. Bear in mind that most mimics do not limit their imitations to potential competing species - they often mimic entirely unrelated species, in completely different feeding guilds.
I am offering an explanation of why some bird species mimic the songs of other species - it keeps the other species out of the mimic’s territory, giving the mimic access to all the resources in the territory (including food).
You seem to have a problem with the fact that most species of birds don’t do this. Yes, most birds sing only the songs of their own species. The fact that most species have not evolved this particular adaptation is not surprising. Chameleons and anoles can change color, but most lizards can’t. Walnut trees secrete a poison that kills nearby plants - most other trees don’t.
It’s easy to explain why mimics don’t limit their songs to those of birds in their own “feeding guilds.” The adaptation is to mimic all the songs the bird hears. In other words, the mimic has a simple learning behavior. If it were to mimic only the songs of birds in its own feeding guild, it would have to either observe the other species to see what they ate, or it would have to be pre-programmed with the songs of competing species. The former is inefficient, and the latter is inflexible. It simply works better for the mimic to imitate every bird song it hears, rather than to try to imitate only those songs of competing species.
Sorry, Jeff, that’s an interesting speculation, but the facts don’t support it.
Even humans can generally distinguish a mimicked song from the real one - it usually differs in quality, or is truncated, etc. Studies generally indicate that mimicked species - whose abilities to distinguish songs undoubtedly exceed humans’ - can distinguish the mimic’s calls from their own, and do not respond to them.
Mimics generally direct their mimicked songs at conspecifics, both male and female, but not the species they are mimicking. (Except in the case of social mimicry of flocking species, as I mentioned above.) Studies have established that repertoire size has clear intraspecific functions, mentioned in my article.
Birds generally do recognize direct competitors, and will chase them out of a territory or away from a food source. Hummingbirds and other nectar feeding birds, for example, will chase all other nectar feeders, regardless of species, out of their territories. Likewise some fruit-eaters, predators, etc. The degree of agression is often directly related to how close a competitor the other species is. If interspecific territoriality was an important function of mimicry, there is no reason to suppose that birds would not mimic primarily the calls of competitors. In fact, where interspecific territoriality does occur, each species will respond to the distinctive calls of the other, not necessarily micmicking them.
There may be limited instances in which a mimicked species coincidentally happens to be a competitor, and may avoid an aggressive mimic such as a Mockingbird. However, this is not a general explanation for mimicry.
Today’s NPR radio show, “The Connection”, had a feature on this subject, with Erich Jarvis, a neurobiologist at DuKe University. He’s studying how hummingbirds can mimic, at the brain cellular level. I’d expect Colibri knows his work. It was a fascinating show: http://www.theconnection.org/shows/2003/01/20030114_b_main.asp
On the same page, there is a link to Dr. Jarvis’ lab page, which has some nice bird brain illustrations, etc.
Yes, here’s a couple more links ( link 1link 2 that talks about Jarvis’ work and vocal learning in hummingbirds. (Although I joked about it in the column, I’m not aware that hummers actually mimic other species. Young birds do learn the songs of conspecifics, though - rather odd, since male hummers do not help raise the young as in many songbirds and so are not around the nest much.)
I’ve sometimes been amazed at hearing certain species of hummingbirds sing. Usually it’s too high pitched to recognize. I suspect that many species are singing part of their songs in registers too high for humans to hear.
This is the most striking aspect to me, from Colibri’s AMNH (link 2) site:
“Working with songbirds in the 1990s, bird researchers added a novel tool to their toolbox, a gene called ZENK, that would make the search for nuclei in hummingbirds much easier. Nottebohm, Mello, and Jarvis noticed that the number of activated ZENK genes in certain areas of the brain was very low when the songbirds were quiet. When the birds sang or heard songs, however, ZENK activity increased. By measuring the levels of activated ZENK in specific locations, the researchers were able to see the previously identified nuclei “in action.” ZENK gave the researchers a window into the brain, enabling them to see how certain behaviors set into motion the molecular activity of cells in specific brain areas.”
That just boggles my mind, the level of intricacy in that work. It sets a lot of groundwork for research into the human brain and language capability, at a molecular level… Dr Jarvis brought up that point, in The Connection interview, that it would be hard to similar research on humans , because you can’t do the necessary brain mapping; ie; dissect after the song. But, it is amazing in it’s findings!
Colibri says:
“I’ve sometimes been amazed at hearing certain species of hummingbirds sing. Usually it’s too high pitched to recognize. I suspect that many species are singing part of their songs in registers too high for humans to hear.”
This was brought up on The Connection show as well. Bats also have their communiques above the human range of ear.
Dr Jarvis used to come to the Wildlife Shelter I worked at when we had a hummingbird that was past hope. we’d call him, and he would make the 40 minute drive , dry ice in tow, to get a tiny hummy brain for his research. I saw a dissection. and it was not the hummy brain that amazed me as much as their EYES. They are huge, comparitively speaking. Who’s doin’ the research on that! Suppose that’s a hijack, but, I’m wondering, Colibri.
Small animals in general have relatively large eyes for their size. This is because the photoreceptor cells that make up the retina in order to work have to be more-or-less the same size regardless of the size of the animal; and because you have to have a certain minimum number of cells in order to get a given level of visual acuity (think of it as pixels-per-inch). Because they are so tiny, hummer’s eyes seem to be especially disproportionate. But I am not aware they have any greater visual acuity than other birds.
However, birds as a group probably have greater visual acuity than any other group, including mammals. Therefore, a hummingbird probably has proportionately larger eyes than you would expect to see in any other organism of the same size.
Thanks, Colibri, and Yumanite, for those answers. I understand the basic bird visual apparatus. I do wonder about the hummingbirds specifically, though. They move so much faster than most other creatures; how can they visually process that speed of input??? That’s what I was wondering in asking for studies on their visual accuity.