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Do Evening Grosbeaks Sing?

Do Evening Grosbeaks Sing?

A while back, I asked in a blog post whether Violet-green Swallows sing — and I answered that they do, because they produce complex repeating strings of stereotyped syllables, even if those syllables don’t sound like much to the human ear.  Now it’s time to ask the same question of the poor, misunderstood Evening Grosbeak, whose vocalizations have often been vastly underappreciated, even by the authors of the BNA account:

Unlike most of their fellow oscines, Evening Grosbeaks do not make much use of the longer, more complex, learned vocalizations (i.e., songs) that characterize the vocal behavior of most songbirds. The Evening Grosbeak seems to be a songbird that doesn’t regularly use songs.

The BNA authors discuss the possibility of Evening Grosbeak song at some length, and by and large I think they do a thorough job of it.  However, much of their analysis rests on a fundamental assumption that song in songbirds must be musical, preferably with trills and warbles attached — and as we’ve already seen many times, that just isn’t true. Not until the end of the article do they really strike pay dirt:

Some observers (L. Elliott pers. comm.; G. Budney pers. comm.) have recorded long series of flight calls, sometimes intermixed with trills, from Evening Grosbeaks. During these sequences, calls (or pairs of calls) are repeated rhythmically at intervals of about 1 s during bouts that can last as long as twenty minutes. Budney reports that long bouts are a regular occurrence at dawn in the Sierra Nevada of California. Perhaps these aggregated, rapid-fire calls act as the functional equivalent of songs during the dawn chorus.

I too have heard song-like strings of flight calls from Evening Grosbeaks (for example, this bird), but I actually feel the best candidate for song in this species is its long strings of trill calls, not flight calls.  In the spring of 2008, Evening Grosbeaks had come out of the higher elevations to invade a number of towns in southern Colorado, and when I stopped in the town of Norwood, I found the place infested with them (along with Pine Siskins and Cassin’s Finches galore).  One male was sitting up atop a small aspen tree, broadcasting his trills to the world:

Evening Grosbeak song, Norwood, CO, 5/13/2008.

These trills are variable, but not randomly so.  In fact, they sort into three well-defined types that we’ll call A, B, and C.  They sound almost identical to the ear, but not quite; if you listen carefully, you can distinguish the order of the male’s calls on this 20-second cut: ABC, ABC, ABC, ABC, ACB, CAC.  When we zoom the spectrogram in, we can see that the differences are subtle, but distinct:

First three calls of the above recording, zoomed and cropped.

The “A” and “B” calls are quite similar at first glance, composed of backwards-L-shaped upslurs, while “C” is obviously distinctive, composed of zigzag backwards-N-shaped notes.  The key distinction between “A” and “B” is that “A” is polyphonic, while “B” is not.  It’s nearly impossible to determine this by looking at the fundamental (that is, the lowest and darkest of the three vertically stacked sounds on the spectrogram), but it becomes obvious when looking at the harmonics (the upper two versions) — the horizontal parts of the call are doubled in “A” and single in “B.”

These differences are not random.  All the “A,” “B,” and “C” calls are stereotyped — that is, they are perfect copies of one another, reproduced with exquisite precision.  Compare the first five renditions of each call on the recording:

The first five "A" calls on the above recording.
The first five "B" calls on the above recording.
The first five "C" calls on the above recording.

The Norwood bird isn’t the only Evening Grosbeak who’s been caught singing on tape.  The Macaulay Library has a couple of recordings [1 2] of singing males recorded a few days apart in central Oregon by Thomas Sander.  The first cut is rather brief, including only sixteen individual trills, but they too fit nicely into “A,” “B,” and “C” categories, much like those of the Norwood bird (click here to see a labeled spectrogram).  The second cut is more extensive, and more impressive — for most of its first three minutes it features an apparently solo singer who incorporates six different trill types instead of three (labeled spectrogram here).

Obviously, more study of Evening Grosbeaks is needed to determine the actual function of these suspiciously song-like vocalizations, but I strongly suspect that they function as male advertising calls.  Hopefully Aaron Haiman, who is currently studying Evening Grosbeaks, can get to the bottom of some of this!

Got Grosbeaks?

Got Grosbeaks?

If this is a common sight at your feeders, Aaron Haiman wants to hear from you. Ontario, Canada, 11/11/2007. Photo by Mike Mills (Creative Commons 3.0).

Aaron Haiman is a Master’s student in Tom Hahn’s lab at the University of California, Davis.  For his thesis research, Aaron is following up on the paper that Tom published with Kendra Sewall and Rodd Kelsey in 2004, the one that described five call types of Evening Grosbeak.

As you will recall, Joseph Grinnell in 1917 recognized five subspecies of Evening Grosbeak on the basis of plumage brightness and bill morphology.  In 1974, the American Ornithologists’ Union decided that some of these subspecies were not distinctive enough, and so they lumped them into the three subspecies currently recognized.  However, the five call variants described by Sewall et al. match up quite well geographically with Grinnell’s original five subspecies.  So Aaron is setting out to determine whether Grinnell’s original taxonomy should be reinstated.  Eventually, he wants to answer lots of interesting questions:

  • do birds of different call types look any different from one another?
  • have they diverged genetically?
  • do other vocalizations vary along with the flight calls?
  • do they have different habitat requirements?
  • do they prefer different foods?
  • do birds of one type respond to the flight calls of other types?

In order to answer all these questions, Aaron needs grosbeaks.  And a great place to find themis at backyard bird feeders.  Aaron has already visited the properties of eight homeowners in three states who reported Evening Grosbeaks at their feeders, and with their generous cooperation, he has set up nets to capture the birds.

Once he captures a grosbeak, Aaron measures it, bands it, takes a sample of its blood, and releases it back into the wild.  Of course, he also audio records the bird’s flight call.  On his recent trip to Colorado, Aaron banded 19 Evening Grosbeaks — which isn’t a bad haul, but much more data is necessary to unravel the mysteries of the biology of this remarkable nomadic finch.

If Evening Grosbeak is a regular visitor to your backyard, and you are willing to host a banding and recording session, please  e-mail Aaron at describing where you live and how many Evening Grosbeaks are coming to your feeders.  So far, Aaron has gotten wonderful support from several generous people willing to open their yards to his research — and if you’re willing and able to help, he would love to hear from you.

Evening Grosbeak Call Types

Evening Grosbeak Call Types

Evening Grosbeak, Soda Springs, CA, 8/3/2009. Photo by C.V. Vick (Creative Commons 2.0).
Evening Grosbeak, Soda Springs, CA, 8/3/2009. Photo by C.V. Vick (Creative Commons 2.0).

In 2004, a paper appeared in the Condor by Kendra Sewall, Rodd Kelsey and Tom Hahn that described several different variants of flight calls in the Evening Grosbeak.  Their fascinating research immediately reminded many of the work on the call types of Red Crossbill, and I heard a few people worry out loud about whether a split of Evening Grosbeak might be in the works.

But there’s no cause for worry.  The “call types” of Evening Grosbeak are not as scary as the call types of Red Crossbill.  While Red Crossbills sort into at least 10 call types in North America, Evening Grosbeaks apparently sort into just 5.  And while multiple Red Crossbill call types often occur in one area (which is part of the justification for splitting them into separate species), the Evening Grosbeak call types usually stay in fairly well-defined, separate geographic ranges.  In fact, Sewall et al. note that the five call type groups seem to match the five subspecies groups in a decades-old taxonomy.

Learning to identify Evening Grosbeak call types is a fascinating exercise, especially if you come upon a wandering flock and want to know where they likely originated.  This post aims to provide an introduction to the different “types” and how to tell them apart.

“Flight calls” vs. “Trills”

The terminology used by Sewall et al. (2004) as well as the BNA account of Evening Grosbeak distinguishes two main calls that are typically heard from the species: “flight calls” and “trills.”  Neither source mentions how the “trills” may vary among groups; this post is going to concern itself solely with the flight calls, which are the most common vocalizations.

Type 1

Range: The northern Rockies and the Cascades, from at least British Columbia south to Oregon, northern Wyoming, and the Black Hills of South Dakota.  Wanders to the northern Sierra Nevada and to Colorado.

Flight call:

Evening Grosbeak Type 1 flight calls, Whitewood, SD.
Evening Grosbeak Type 1 flight calls, Whitewood, SD, 11/20/2007.

Even though the spectrogram shows that it tends to start at a higher frequency than other types, Type 1 sounds relatively low-pitched, especially compared to Types 2 and 4.  It  has a very clear sound that is distinctive once you learn it.  More than the other types, this one reminds me of a particular Pine Siskin call (but beware!  Pine Siskins can mimic other Evening Grosbeak types in their songs).  Here’s another good recording of Type 1.

Type 2

Range: The Sierra Nevada of California; wanders at least occasionally north to southern Washington.

Flight call:

Evening Grosbeak Type 2 flight calls, California.
Evening Grosbeak Type 2 flight calls, Sierra County, CA, 6/14/2004 and 6/16/2004.

To my ear, this sounds like the clearest, most purely whistled type, even clearer than Type 1, but it is distinctly higher-pitched and more piercing than Type 1.  Type 2 is quite similar to Type 4 and the two may be difficult to distinguish by ear in the field (see below).

Type 3

Range: Boreal forests of Canada east of the Rockies and in the northeastern United States.  Wanders south throughout the East.

Flight call:

Evening Grosbeak Type 3 flight call, Canada.  Recording by Chris Parrish on Xeno-Canto (click for link).
Evening Grosbeak Type 3 flight call, Sanguenay, Quebec, 5/21/2007. Recording by Chris Parrish on Xeno-Canto (click for link).

The distinctive Type 3 differs from Types 1, 2, and 4 by being slightly longer and lower-pitched and distinctly burry.  Field guides with an eastern focus have often compared the calls of Evening Grosbeak to certain vocalizations of House Sparrow, and Type 3 is the reason why.

Type 4

Range: The southern Rockies (Colorado and New Mexico), occasionally wandering north at least to the vicinity of Jackson Hole, Wyoming.

Flight call:

Evening Grosbeak Type 4 flight calls, Colorado.
Evening Grosbeak Type 4 flight calls, Delta County, CO, 3/9/2008.

The high-pitched and piercing Type 4 flight calls are most similar to Type 2 flight calls, both on the spectrogram and to the ear, but slighty huskier and less clear.  I’m not certain I could tell them apart in the field with confidence, but the two have never yet been recorded in each others’ range to my knowledge.  Here’s another recording of Type 4.

Type 5

Range: The Sierra Madre of Mexico, north to southeastern Arizona.

Flight call: To my knowledge, only one recording of this type has been made, and here it is:

Evening Grosbeak Type 5 flight call, Arizona.  Recording by Rich Hoyer (used here with permission).
Evening Grosbeak Type 5 flight call, Cochise County, AZ, 4/14/1999. Recording by Rich Hoyer (used here with permission).

If this recording is typical, then Type 5 is distinctive: even longer and burrier than Type 3, but high-pitched like Types 2 and 4.  If I had to guess, I’d say that the doubled rhythm is probably due to the whim of this individual bird, not characteristic of Type 5 in general, but who knows? — maybe Type 5 is the Mountain Pygmy-Owl of Evening Grosbeaks.  If you have any recordings of Evening Grosbeak from Arizona or Mexico (or you know someone who does), please let me know!

Regions of Mystery

There are some places where we don’t really know which type to expect:

  • Southwest Oregon and northern California: Types 1 and 2 have both been recorded in this region, and the actual limits of their distribution here are poorly known.
  • Black Hills of South Dakota: The one recording I have is of Type 1, but I think Type 3 might also be likely, and Type 4 might wander in.
  • Arizona: My guess would be that Type 4 is most common in the northern and central parts of the state, while Type 5 is the most likely type to be encountered in the southeastern mountains, but we need more data.

You know what that means: more recordings necessary!