Earbirding

During my research for the last couple of blog posts, I’ve arrived at a surprising conclusion: when it comes to regional variation in calls, few common birds are as poorly understood as the White-breasted Nuthatch, particularly the Rocky Mountain and Pacific populations.

In the first two parts of this series we explored the “quank” calls, which are some of the most common vocalizations of the three populations, and the “fast songs.”  Today we’ll investigate two more types of rapid-fire calls, the “rapid quanks” and the “hit-trills,” and then I’ll leave the subject of nuthatches alone for a little while!

Rapid Quanks

The term “rapid quank” was coined by Ritchison (1983) to describe the long strings of calls that eastern nuthatches would give in high agitation.  The “rapid quanks” are a little tricky to compare among the three populations, because they grade into the regular “quanks,” the “fast songs,” and even the “hit-trills” (see below).  In some ways “rapid quank” is just a catch-all term for agitated calls.

In my search through all the recordings available to me, the “rapid quanks” of Pacific birds have been the hardest to find.  I suspect this is due to a relatively small sample size rather than a lack of “rapid quanking” by Pacific birds, but I’m not entirely certain of that.  (Note, however, some very excited Pacific birds failing to rapid-quank on this recording.)

Above are some relatively rapid short notes from a bird near its nest in California.  By comparison, the Rocky Mountain birds sound like they’re on speed:

Especially when they get a little bit upset:

As far as I know, nothing but a “Rocky Mountain” White-breasted Nuthatch ever gives notes at this frantic rate (up to 25-30/sec).  This type of vocalization is highly variable, however, and I particularly recommend checking out a couple of other distinctive recordings of it, here and here (the latter recording, in particular, is repeated so many times in a row that it could be functioning as a kind of song).

When the “Eastern” nuthatches get excited, they’re still much slower, along the lines of the “Pacific” birds:

This is about as crazy as they get (in response to an Eastern Screech-Owl tape):

For extra credit, you can listen to more fast-quanking Eastern birds here and here.  Note the tendency to revert to paired notes, the “double quanks” of Ritchison (1983), whenever the bird “catches a breath.”  Again, beware confusion with the diagnostic disyllabic quanks of Rocky Mountain birds.

Hit-trills

Ritchison (1983) didn’t mention a “hit-trill” vocalization, but he did identify a short contact note he called the “hit,” which is frequently extended into a trill, so I figured the name wasn’t much of a stretch.  This is a rather quiet call given in close contact with other nuthatches, and it is very similar in all three populations, although like most of the other calls, it appears to increase in pitch from east to west, and increase in speed in “Rocky Mountain” birds:

Click here to listen to the above (at 1:15).

Last time we looked at the most common calls of the three populations of White-breasted Nuthatch.  Here in Colorado, we have both the “Rocky Mountain” and “Eastern” forms of the White-breasted Nuthatch, and I’ve heard a couple of people proclaim that any bird giving a rapid-fire series of calls is a Rocky Mountain individual, while any bird giving a single “yank” note is an Eastern.  Unfortunately, it’s more complicated than that.  All three populations of the species give rapid series of calls from time to time, so the first thing you’ve got to figure out is which type of call you’re listening to.

Since White-breasted Nuthatches have a lot of different call types, it will probably require several posts to discuss them all.  Over the course of this series we’ll mostly follow the terminology of Ritchison (1983) in our discussion of “fast songs,” “slow songs,” “rapid quanks,” and “hit-trills.”  Today’s installment looks at the “fast songs.”

Fast songs

Ritchison distinguished between “slow songs” (which we’ll explore in a later post) and “fast songs.”  Fast songs consist of rapid strings of simple overslurred nasal notes at a rate of about 10 notes/second, and they appear to be similar in all populations of the White-breasted Nuthatch:

(click here to listen to the above recording at the Macaulay Library)

The length, rate and pitch of fast songs are fairly variable within groups, as far as I can tell, but there appears to be a general trend of increasing pitch as you move from east to west. With more investigation, these differences may turn out to be systematic.

How can you tell when you’re hearing a fast song as opposed to some other vocalization?  Two ways:

1. Rhythm. Fast songs contain long strings of single notes (not double notes like in the “disyllabic quank” call of Rocky Mountain birds)  in strict rhythm (not accelerating or decelerating).
2. Behavioral context.  According to BNA, fast songs are given by males hoping to attract a mate; they are often sung loudly many times in a row in late winter and spring. This behavioral context helps differentiate them from some of the “rapid quanks” we will see next, since the two types of vocalizations seem to integrade.

The take-home lesson: long strict series of single nasal notes don’t necessarily identify a bird as a member of the “Rocky Mountain” group.  Double notes in series, though, are a good indicator — see the last post for an example.

More on nuthatches to come.  Stay tuned.

Birders have known for a number of years now that White-breasted Nuthatches sort out into three distinct vocal groups in North America — Pacific, Rocky Mountain, and Eastern — following a pattern of three-way separation that mirrors those of several other bird species, including the Solitary Vireo complex (split into Cassin’s, Plumbeous, and Blue-headed) and the sapsuckers (split into Red-breasted, Red-naped, and Yellow-bellied).

However, with the exception of field guides, the ornithological literature has been silent on this point.  Nobody has done a systematic study on the marked regional variation in vocalizations of the White-breasted Nuthatch.  The only in-depth study on vocalizations in the species was done by Gary Ritchison in Minnesota, and so the vocalizations of the Eastern form have been the only ones described in the literature for years; they were the only ones available on commercial bird sound recordings for years too.  Even though the Birds of North America account was revised by its authors in 2008, they made no mention of vocal variation, which seems a shocking oversight.  Spellman & Klicka (2007) published a molecular phylogeny of the species and found evidence for four distinct clades in the species, with boundaries exactly matching those of the vocal groups (except that they found the Rocky Mountain group was divided into two clades, apparently with identical vocalizations).

Thus, since I can’t find this information anywhere else, starting with this post, I’m going to start exploring these vocal differences in some depth.

“Quank,” etc.

Here are the most common calls of the three nuthatch groups.  For simplicity’s sake, we’ll always travel left to right across the country, so you’ll always see Pacific, Rocky Mountain, and Eastern birds in that order.

The first thing you’ll notice is that the Pacific and Eastern birds sound much more similar to one another than they do to the Rocky Mountain birds. Thus begins a theme we will see repeated many times.  Spellman & Klicka found that the Pacific and Eastern birds were sister taxa, separated from one another by the less closely-related birds in the Mountain West.  If this seems surprising, remember that the Solitary Vireo complex follows a similar pattern, with Cassin’s and Blue-headed Vireos looking and sounding more like each other than like Plumbeous.

The calls you see above are variable in each of the groups, so some of the differences you see between Pacific and Eastern in call length and overall inflection may not always apply.  The most consistent difference seems to be one of pitch: the Pacific birds, with their more widely spaced partials, sound a lot higher-pitched than their huskier-voiced, more nasal Eastern cousins.

Identifying the Rocky Mountain birds, meanwhile, seems like a slam-dunk.  Eastern and Pacific birds never make rapid-fire series of call notes, right?  Well, actually, yes they do — several different kinds, in fact.  I’ll be looking at those in my next post!