Song of the Rifleman

As an avid birdwatcher, I've learned many of the vocalizations of our local species.  Some, especially the migratory species we only hear from May to September, I have to relearn every year, but a few of them are so distinct that my ears perk up whenever I hear them.  One of my favorites is the whirling, ethereal song of the Veery (Catharus fuscescens):

Another lovely one, often heard in the same sorts of deep-woods habitats as the Veery, is the Wood Thrush (Hylocichla mustelina):

By far the strangest bird songs I've ever heard, though, we came across when we visited the lowlands of eastern Ecuador about twenty years ago.  There were two we heard but never saw -- first, the aptly-named Screaming Piha (Lipaugus vociferans), which can be heard for miles:

And second, the Great Potoo (Nyctibius grandis), which is cryptically-colored and nocturnal, so they're almost never seen.  But when they sing at night... holy crap.  Imagine being out in the jungle, alone, at night, and hearing this:

It's no wonder the locals thought there were monsters out there.

Bird songs serve two main purposes.  They're territorial defense signals and mate attractants.  (Which led a former student of mine to say, in some astonishment, "So birds only sing when they're mad or horny?")  Songs are usually only done by males, and mostly during the breeding season.  Calls, on the other hand, are done by both males and females, at any time of the year, and can mean a variety of things from "there's food over here" to "watch out for the cat" to "hey, howsyamommaandem?"  (The latter mostly from birds in the southeastern United States.)  Those of you in the eastern half of North America certainly already have heard the difference; our local Black-capped Chickadee (Poecile atricapillus) has a call, the familiar "chicka-dee-dee-dee-dee" that gives the species its name, and a song -- a two-note whistle with the second note a whole step below the first.  Listening to them, you'd never guess it was the same bird.

There's an interesting distinction in how animals vocalize.  Some vocalizations seem to be innate and hard-wired; the barking of dogs, for example, doesn't need to be learned.  A great many bird species, however, including songbirds and parrots, learn vocalizations, and deprived of examples to learn from, never sing.  (This includes the amazing mimicry of birds like the Australian Superb Lyrebird (Menura novaehollandiae), which can learn to imitate not only birdsongs but a huge variety of other sounds as well):

The topic comes up because of a study that came out this week in the journal Communications Biology about the Rifleman (Acanthisitta chloris), a tiny species from New Zealand that is one of only two surviving species in the family Acanthisittidae, the New Zealand wrens, which are only distantly related to the more familiar and widespread true wrens.  (If you're curious, its odd common name comes from the cheerful colors of the plumage, which someone decided looked like a military uniform:

[Image licensed under the Creative Commons digitaltrails, Lake Sylvan - Rifleman (5626163357) (cropped), CC BY-SA 2.0]

The Rifleman is not a songbird, and (if the preceding distinction holds) should be unable to learn vocalizations; any sounds it makes should be instinctive and fixed, like the clucking of a chicken.  But the study found that there were variations in the vocalizations of different individuals, and those variations were independent of how closely related they were; what mattered was how nearby they lived to each other, implying that the alterations in sound were learned, not innate. 

"The vocal behavior that we were unravelling in this study is very similar to what is known as vocal accommodation in human linguistics," said Ines Moran, of the University of Auckland, who led the research.  "It's similar to our ability to adjust our ways of speaking in different social, dialectal, or hierarchical settings -- modulating our voices to better fit in certain social groups."

So bird vocalizations may not be as simple as we'd thought.  Like most things, I suppose.  It brings up the silly distinction that I heard over and over again from students, that there's a split between "human" and "animal."  We're clearly animals; and, conversely, what we call "animals" share a great deal more with us than we often realize.  We have a lot to learn from the other species we whom we cohabit the planet.  It's nice that we're beginning to pay more attention.

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