A Comparison of the Vocal Repertoires
of Willow Flycatcher (Empidonax traillii)
and Alder Flycatcher (Empidonax alnorum)

D. Archibald McCallum, Ph.D.
Applied Bioacoustics
Eugene, Oregon

Display Repertoire in Two Side-by-side Scrollable Frames

TABLE OF CONTENTS

MAIN ELEMENTS OF REPERTOIRE

WIFL Song-types
WIFL Fitzbew   WIFL Fizzbew   WIFL Creet  

ALFL Song-type
ALFL Feebeeo  

Zweeoo Call
WIFL Zweeoo   WIFL Zweeoo   ALFL Zweeoo  

Weeoo Call
ALFL Weeoo   WIFL Weeoo   WIFL Weeoo   WIFL Bew  

Churr and Trill Calls
ALFL Churr   WIFL Churr   WIFL Trill   ALFL Trill  

Call Notes
ALFL Pip   WIFL Pip (Pip)   WIFL Whup   WIFL Whit  

Double-Peak Call
ALFL Double-Peak   WIFL Double-Peak  

COMBINATIONS OF MAIN ELEMENTS

ALFL Pip + Weeoo
WIFL Whit + Weeoo
ALFL Complex Call
ALFL Undescribed Descending Twitter   WIFL Undescribed Descending Twitter



SOUNDS
1.  WIFL Fitzbew
Introduction     Table of Contents     Side-by-side Comparison

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Figure 1. WIFL Fitzbew, 6/25/1994, Missoula, Missoula County, Montana. ã D. A. McCallum. "P1" = Phrase 1, etc. The phrases are presumed homologous in Fitzbew and Fizzbew.

Significance for identification of species. This is probably the song-type that most birders depend upon for identification of Willow Flycatcher. It is diagnostic, but is not always given. Knowing about, and being able to distinguish, the similar sounds (see below) from Fitzbew is a good idea. That makes it possible to identify the species by song variety in many cases. Be ready for ALFL Pip-Weeoo.

Distinguishing features. The first two notes ( P1) can be resolved aurally, although occasionally they are connected, with the frequency trace rising above 7 kHz. (WIFL Whit seems derived from this phrase.) The long final phrase (P3) is typically preceded by two isolated clicks and one that is continuous with P3. These clicks no doubt contribute to the overall aural effect but are not likely to be resolved aurally by most listeners. In the western subspecies adastus and brewsteri the third click of P2 grades into the final sound, resulting in a rapid upsweep in pitch trend, as seen above; in other areas the third click is clearly separated from P3, which descends throughout its length. P3 changes form about one-third of the way through, indicative of a change in the rate and continuity of frequency modulation (periodic variation in pitch). The initial third is actually a series of very- closely-spaced "v-shaped" notes. This section of the phrase is low in amplitude in this example, but this is not typical. The final two-thirds of P3 is continuous, oscillating over a 2-kHz range every hundredth of a second. This modulation is slower than any modulation in the repertoire of the Alder Flycatcher. (In E. t. extimus this modulation is slower yet.) According to Stein (1963:24), Fitzbew is given with "two major throwbacks of the head."

Nomenclature: Many names have been applied to this sound, and some of them may be more onomatopoeic, but "Fitzbew" is one of the most firmly-established birdsong names in North America. It was also used in the 1960s and early 1970s to designate the as-yet-unnamed species that eventually became the Willow Flycatcher. Fizzbew is a distinct sound, not a variant of Fitzbew. Both are stereotyped and equally common, deserving equal billing in field guides. This has been known since 1963 ( Stein 1963).

Similar sounds. WIFL Fizzbew: Phrase 1 is a continuously-rising buzzy trill, mirroring Phrase 3. Phrase 2 usually has one isolated click instead of two. WIFL Zweeoo: like a brief Fizzbew but beginning with a series of clicks. Luckily, ALFL Zweeoo is less similar. ALFL Pip-Weeoo: This combination sounds surprisingly similar to Fitzbew. The Pip is continuous, not broken as is "Fitz." The leading part of Weeoo is continuous, not broken into two or three clicks. Despite these differences, and its briefer duration, Pip-Weeoo can cause trouble.

Combinations. Combined with Fizzbew and Creet in advertising song.


2.  WIFL Fizzbew
Introduction     Table of Contents     Side-by-side Comparison

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Figure 2. WIFL Fizzbew, 7/10/2007, Deer Lodge, Powell County, Montana. ã D. A. McCallum. "P1" = Phrase 1, etc. The phrases are presumed homologous in Fitzbew and Fizzbew.

Significance for identification of species. This song-type is very similar in duration, bandwidth, and pitch-trend to Fitzbew, but being able to distinguish the two is useful for field identification. The use of two similar song-types by Willow Flycatcher distinguishes it from Alder Flycatcher. Also, Fizzbew is very similar to WIFL Zweeoo (Figure 4, Figure 5), so recognizing the latter certainly requires distinguishing Fizzbew from Fitzbew. Because of the rolling, ascending "Fizz" phrase, Fizzbew is more similar to ALFL Feebeeo than is Fitzbew. Be ready for a bird giving Fizzbew only, which is unlikely but possible.

Distinguishing Features. Field guides typically mention Fitzbew, then describe it as variable. That is not actually an accurate characterization of WIFL song-types. The three discrete song-types are each quite stereotyped, and not very variable at all. Fizzbew typically rises to a higher frequency (pitch) than Fitzbew. The "Bew" (P2 + P3) of Fizzbew is very similar to the "Bew" of Fitzbew and appears homologous to it, but P2 typically has one isolated click (plus one basted to P3) instead of two and the "v-shaped" notes in the first third of P3 are consistently farther apart than in the corresponding part of Fitzbew. As with Fitzbew, the onset of P3 differs between the northern western populations (adastus and brewsteri) and other populations (eastern traillii and campestris and southwestern extimus). P1 is a trill, an ascending series of very brief (5 msec), "v-shaped" notes separated by equivalent (6 msec) silent gaps. In contrast, the "burry", rising notes of the Alder Flycatcher are all continuous sounds with zigzag spectrographic traces, like the final, descending, part of "Bew."

Nomenclature: Some field guides do not name this sound, perhaps leading many birders to assume that the song (Fitzbew) of WIFL is more variable than the song (Feebeeo) of ALFL. Actually, Fitzbew and Feebeeo are equally stereotyped, but the song repertoire of WIFL is more diverse, with three song types rather than one.

Similar sounds. WIFL Fitzbew: Starts with two loud clicks, and P2 has two isolated clicks instead of one. WIFL Zweeoo: very similar, but noticeably shorter. The similarity is in the first, ascending phrase. In Fizzbew, the "Bew" is long and seems accented, while in Zweeoo the final phrase is short and insignificant. ALFL Feebeeo: Similar enough to confuse; rely on songtype variety in WIFL and ascending second phrase of Feebeeo. If you have very good temporal discrimination, listen for the click in the middle of Fizzbew, which is absent in ALFL Feebeeo.

Usage. With Fitzbew and Creet in advertising song.


3.  WIFL Creet
Introduction     Table of Contents     Side-by-side Comparison

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Figure 3. WIFL Creet, 6/14/2006, Elkton, Douglas County, Oregon. ã D. A. McCallum.

Significance for identification of species. This brief sound is easily overlooked, but it is a full-fledged element of the advertising song of Willow Flycatcher. Hearing it along with Fitzbew and/or Fizzbew cinches the identification of Willow Flycatcher. It is not likely to be given repeatedly without Fitzbew or Fizzbew. It is quite similar in duration, pitch trend, and quality to ALFL Zweeoo, but Alder Flycatcher usually does not use its Zweeoo call in its singing performances. ALFL Zweeoo and WIFL Creet are easily distinguished with spectrograms.

Distinguishing features. Creet begins with a series of faint clicks (like ALFL Zweeoo), which are followed by brief "v- shaped" notes very similar to those in the opening "fizz" of Fizzbew. Then there is a silent gap. This is real, and is consistently present throughout the range of the Willow Flycatcher. The final part is a series of very brief "v-shaped" notes that may or may not be connected. According to Stein ( 1963:24), Creet is given with "a single throwback of the head."

Similar sounds. ALFL Zweeoo: Similar in duration and bandwidth, but continuous. WIFL Zweeoo: First phrase is continuous, without break seen above, and it has a second, descending, phrase. ALFL Feebeeo: "Fee" phrase is similar in duration and bandwidth but continuous, and the entire sound is much longer.

Combinations. With Fitzbew and Fizzbew in advertising song.


4.  WIFL Zweeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 4. WIFL Zweeoo, 7/10/2007, Deer Lodge, Powell County, Montana. ã D. A. McCallum .The same bird gave Fitzbew and Fizzbew.

Significance for identification of species. This is the sound that is most likely to lead to the misidentification of a Willow Flycatcher as an Alder. This is a serious issue on the west coast, where Alders probably are rare spring migrants, but under-reported. When used, Zweeoo may be the only field mark available. It is used mostly for nest defense, but sometimes is given repetitively from a conspicuous perch, in the manner of advertising song. Its aural similarity to ALFL Feebeeo, combined with the repetition of the same call, which is reminiscent of singing by Alder Flycatcher, invite error. The Southwestern Willow Flycatcher's version of this call (not presented here) appears sufficiently distinctive to allow identification of that subspecies from this call alone.

Distinguishing features. The initial, ascending half of the call begins like a WIFL Creet (with faint clicks) and then resembles the "Fizz" of Fizzbew (with an ascending series of closely-spaced "V-shaped" notes). The absences of a silent gap and of more closely-packed notes at the end distinguish this half from Creet. The second half is nothing more than the call-type called Weeoo by Stein (1963) and Writ-tu by Sedgwick (2000). WIFL Weeoo is similar to ""Bew"", but is consistently different as follows: (1) The first part of P3 of "Bew" is absent in Weeoo. (2) The descending buzz in Weeoo covers the same frequency range as the final part of "Bew"," but each oscillation lasts 5-6 msec rather than 10 msec, i.e., it is modulated faster. ALFL Weeoo is similar to but distinguishable from WIFL Weeoo (Writ-tu). ALFL Zweeoo is continuous, and easily distinguished from this call.

Similar sounds. Fizzbew: Similar, but noticeably longer in duration then Zweeoo. In Fizzbew, the second phrase ("Bew") starts at a higher pitch than the end of the first phrase ("Fizz"); the second phrase of Zweeoo starts lower than the end of the ascending first phrase. ALFL Feebeeo: Also noticeably longer in duration. The "Fee" and "O" parts are not very different from the two parts of WIFL Zweeoo. It is the middle, "Bee" phrase that sets Feebeeo apart from WIFL Zweeoo. It makes the entire sound longer, and rises to a higher pitch than Zweeoo, giving Feebeeo a more ascending and higher sound. Creet: Creet is similar to first half of Zweeoo, but is broken rather than continuous. WIFL Weeoo and ALFL Weeoo: both resemble second half of this call (see above).

Usage. Often a stand-alone call (repeated, not mixed with other call- types). May be combined with Whit (which may be given by the mate), and occasionally with rare calls that are not stereotyped parts of the repertoire.


5.  WIFL Zweeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 5. WIFL Zweeoo, 6/6/2006, Rhinehart Lane, Union County, Oregon. ã D. A. McCallum. Numerous Zweeoos and some Whits were heard from this location. Note the faint Whit (made by a nontarget bird) before the Zweeoo. It is audible on the cut.

This example has no leading clicks, and the leading part of the second half is continuous. Otherwise it is similar to the example in Figure 4.


6.  ALFL Zweeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 6. ALFL Zweeoo, 6/14/1993, Anchorage, Anchorage Borough, Alaska. ã D. A. McCallum.

Significance for identification of species. This rarely-heard call appears to be used in nest defense, like WIFL Zweeoo (Stein 1963:31). Auditors experienced with the complete repertoires will find it sufficient to identify this species.

Distinguishing features. This call resembles WIFL Creet, and may be homologous with it. It is distinguished from WIFL Zweeoo, which may not be its homologue (contra Stein 1963), by the absence of a break between the rising and falling portions of the call. It starts with a series of clicks, like those of WIFL Creet. These are followed by a continuous note that oscillates in frequency as pitch trend ascends; the oscillations then collapse into a narrow band and the note descends in pitch. The clicks of Zweeoo are similar to those at the beginning of ALFL Feebeeo. The rest of the call is very similar to the "Bee-o" portion of Feebeeo, minus the final buzz and click (see Figure 7). Thus, ALFL Zweeoo resembles a shortened Feebeeo song, just as WIFL Zweeoo resembles a shortened Fizzbew song.

Similar sounds. WIFL Creet: broken just before the peak. Also, the ascending part is a series of closely-spaced V-shaped notes, while the ascending part of this sound is continuous (i.e., the V's are connected). WIFL Zweeoo: clearly two parted. ALFL Weeoo: ends rather than begins with sawtooth buzzy sound.

Usage. Usage is unclear. Stein (1963) recorded it in response to playback of Feebeeo. It is given spontaneously by birds that are not singing (pers. obs.). Perhaps it is used for nest defense, like WIFL Zweeoo.


7.  ALFL Feebeeo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 7. ALFL Feebeeo, 6/13/1962, Stowe, Lamoille County, Vermont. Borror Laboratory of Bioacoustics Cut 5900. ã Borror Laboratory of Bioacoustics, used with permission.

Significance for identification of species. This is the diagnostic sound by which most Alder Flycatchers are recognized. Although the repertoire of the species is large, this is by far the most commonly-heard sound. Being able to distinguish Feebeeo from WIFL Fizzbew and several calls of both species is essential. WIFL Fitzbew is so different that it should pose no problem.

Distinguishing features. The "Fee" part comprises a series of clicks, followed by a continuous note that oscillates in frequency as it ascends in pitch trend, followed by a chevron (ascending then descending frequency). The second major part ("Beeo") oscillates in frequency as pitch trend increases , does not oscillate as pitch trend drops very rapidly, and then oscillates again at the low terminal pitch. This is a single, continuous note. The ascending part is the "Bee" and the descending part is the "O." (See Kroodsma (1984).) The final descending click of Feebeeo is aurally unimportant (to humans); it is not the "O" of "Beeo." Note that amplitude increases throughout the "Fee," but increases and then decreases in "Beeo." The amplitude graph of WIFL Fizzbew is quite similar. Focusing on the "accent" of these sounds may not be helpful. (The amplitude spike in the rapidly descending part of "O" is widespread, but especially loud in this example.) According to Stein (1963:23), "This pattern is given with a single major throwback of the head, with a short jog at the bee."

Kaufman (1990) goes into more detail than other field-guide authors: "The song is strongly accented on the second syllable, which sounds both louder and higher pitched than the first." (Kaufman 1990:205) The pitch trend is clearly up through most of the song. I would conjecture that the sense of an "accent" comes from the sharp decline in frequency at the beginning of the "O" note.

Similar sounds. WIFL Fizzbew: about the same duration. Listen for the equal-duration ascending and descending pitch trends. Feebeeo rises steadily and then falls suddenly. WIFL Zweeoo is very similar. Its second half is similar in form to the "O" note of Feebeeo, and the two begin similarly. The main difference is that Feebeeo has the "Bee" note and WIFL Zweeoo does not. This gives Feebeeo a much longer ascending arm, and also its peak pitch is higher.

Usage. Usually not combined with other repertoire elements. Repeated monotonously in advertising song. Occasionally (Stein 1963, DAM pers. obs.) it is combined with Double-Peak in advertising song.


8.  ALFL Weeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 8. ALFL Weeoo, 8/1/1956, Cutler, Washington County, Maine. Borror Laboratory of Bioacoustics Cut 2226. ã Borror Laboratory of Bioacoustics, used with permission. This sound was extracted from a Complex Call, but it also occurs singly in nature.

Significance for identification of species. This call is given rather infrequently, but when it is it may not be accompanied by more familiar ALFL vocalizations. It can be recognized by the smooth initial part and the relatively soft and brief buzz at the end.

Distinguishing features. Weeoo is essentially a large Pip (or Whup) basted to a "saw-toothed" buzz in both ALFL and WIFL. The rounded top of the Pip and the evenness of the frequency modulation in the buzz are distinctive characteristics of the ALFL version.

Similar sounds. WIFL Weeoo: has uneven frequency modulation over greater bandwidth, initial part may be sharp-peaked, sounds much rougher. ALFL Churr: lacks the high arching initial part. ALFL Double-Peak: has two smooth Pips instead of one.

Usage. ALFL Weeoo is used singly and in combination as part of a stereotyped complex call. Stein (1963, Fig.6) presented a combination of Trill and Weeoo. He referred to all such combinations of Trill and other calls as Churr. Also combined with Pip to make a sound that is similar to WIFL Fitzbew.


9.  WIFL Weeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 9. WIFL Weeoo (=Writ-tu), 5/19/1963, Columbus, Franklin County, Ohio. Borror Laboratory of Bioacoustics Cut 6384 ã Borror Laboratory of Bioacoustics, used with permission. This is a noisy recording; WIFL Weeoo is rare in nature.

Significance for identification of species. This call is not very useful for identification, because it is rarely given. It is, however, distinguishable from any sound of the Alder Flycatcher. The Southwestern Willow Flycatcher's version of this call (not presented here) appears sufficiently distinctive to allow identification of that subspecies from this call alone. WIFL Weeoo is a component of WIFL Zweeoo, which is given fairly commonly.

Distinguishing features. Essentially a Whup basted to a buzz (Sedgwick 2000). The buzz is uneven in frequency bandwidth. WIFL Weeoo is the second half of WIFL Zweeoo.

Nomenclature: This sound is called "Writ-tu" by Sedgwick (2000). Although that name may be more onomatopoeic than Stein's (1963) Weeoo, I prefer to retain the latter because of the similarity between WIFL Weeoo and ALFL Weeoo. They appear to be homologous. WIFL Weeoo may be thought of as simply a part of WIFL Zweeoo, but a similar relationship between ALFL Weeoo and Zweeoo does not hold. WIFL Weeoo is rare, whereas WIFL Zweeoo is fairly common.

Similar sounds. ALFL Weeoo: final part has even frequency modulation, at slightly slower rate, over narrower bandwidth, initial part rounded and drawn out, dominating the sound; sounds more like a Double-Peak than this. Some WIFL Weeoo (see Figure 10) are quite similar to ALFL Weeoo and may not be safely distinguishable aurally. WIFL Double-Peak: has two smooth Pips, the initial Pip here is too brief to register.

Usage. Occasionally heard, usually interspersed with songs and Trill in hyperactive behavior, perhaps during incursions into calling bird's territory.


10.  WIFL Weeoo
Introduction     Table of Contents     Side-by-side Comparison

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Figure 10. WIFL Weeoo (=Writ-tu), 7/09/2006, Nutria, McKinley County, New Mexico. ã D. A. McCallum.

Distinguishing features. This example of Weeoo is more rounded at the beginning, and may not be safely distinguishable from ALFL Weeoo. Spectrographically, the longer duration and uneven bandwidth of the buzzy (frequency-modulated) part distinguish it from ALFL Weeoo.


11.  WIFL Bew
Introduction     Table of Contents     Side-by-side Comparison

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Figure 11. WIFL "Bew," 7/18/2004, Izaak Walton Road, near Eugene, Lane County, Oregon. ã D. A. McCallum.

Significance for identification of species. Occasionally a "Bew" appears by itself and is used like Weeoo. Although such "Bews" tend to be flatter (spectrally) than "Bews" that occur with "Fitz" or "Fizz," they are clearly recognizable as such spectrographically, and readily identified to species. Hearing this rare sound without other cues, though, could be confusing.

Distinguishing features. This sound is longer in duration than Weeoo, and has both P2 and P3 of "Bew" (see Figures 1 and 2). P3 does not descend in pitch, unlike P3 of Fitzbew and Fizzbew. In this respect, this sound resembles Weeoo in comparison to the second half of Zweeoo. Probably these patterns illustrate a phonological rule: if the first part doesn't ascend, the second part doesn't have to descend. When there is no first part, as in Weeoo, pitch trend is flat. This example is probably derived from Fitzbew rather than Fizzbew, in that is has two introductory notes.

Similar sounds. This sound has the same relationship to Fitzbew that WIFL Weeoo has to WIFL Zweeoo.

Usage. Like WIFL Weeoo, along with trills in hyperactive calling. May also be associated with perch changes.


12.  ALFL Churr
Introduction     Table of Contents     Side-by-side Comparison

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Figure 12. Two ALFL Churrs, 7/26/2006, Black Balsam (Mountain), 5803 feet elevation, Haywood County, North Carolina. ã D. A. McCallum.

Significance for identification of species. More study is needed, but the forms presented above do not appear to be used by Willow Flycatchers. Nonetheless, some WIFL sounds are so similar that determination of species on the basis of Churr is not recommended.

Distinguishing features and nomenclature. Stein (1963) gave the name "Churr" to strings of Pips that are punctuated with rough sounds, such as Weeoo. It seems better to follow Sedgwick (2000) and interpret these as combinations of trills and various rough sounds from the repertoire. In the Alder Flycatcher, some of these rough sounds are distinguishable from Zweeoo and Weeoo, and I refer to them as "Churr." The consistent feature of Churr is the evenly modulated buzz lasting around 100 msec and the absence of the high- arching initial sweep that characterizes Weeoo. ALFL Weeoo is quite stereotyped. Although Churr is more variable, the initial notes in the two examples above are stereotyped and seen throughout the geographic range of ALFL; e.g., spectrograms with shapes like these are presented by Stein (1963, Figure 6).

Similar sounds. WIFL Churr: Too rare to be characterized, but the initial notes in the two Churrs above appear to be restricted to ALFL. WIFL Weeoo is intermediate between these sounds and ALFL Weeoo.

Usage. With Pip and Trill, the entire indeterminate combination called "Churr" by Stein.


13.  WIFL Churr
Introduction     Table of Contents     Side-by-side Comparison

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Figure 13. WIFL Churr, 7/01/2007, Hooper Lane, Henderson County, North Carolina. ã D. A. McCallum.

Significance for identification of species. This sound is so rarely used that its significance is difficult to gauge. It probably is not distinguishable from ALFL Churr. This sound may not deserve classification as a distinct call type.

Distinguishing features and nomenclature. Stein (1963) gave the name "Churr" to strings of Pips that are punctuated with rough sounds, such as Weeoo. It seems better to follow Sedgwick (2000) and interpret these as combinations of trills and various rough sounds from the repertoire. In the Alder Flycatcher, some of these rough sounds are distinguishable from Zweeoo and Weeoo, and I refer to them as "Churr." The consistent feature of ALFL Churr, which I judge to be used fairly commonly, is the evenly modulated buzz lasting around 100 msec and the absence of the high-arching initial sweep that characterizes Weeoo. Stein (1963) figures similar sounds for Willow Flycatcher, but I wonder if they are misidentified ALFL calls. In my experience, such sounds are rare in WIFL, and this is the only example I have found that is not interpretable as WIFL Weeoo or WIFL Bew, which is used by this species in the manner of ALFL Churr.

Similar sounds. ALFL Churr: very similar. WIFL Weeoo has an initial chevron, as does ALFL Weeoo.

Usage. With Pips and Trills, the entire indeterminate combination called "Churr" by Stein.


14.  WIFL Trill
Introduction     Table of Contents     Side-by-side Comparison

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Figure 14. WIFL Trill, 6/6/2007, Princeton, British Columbia. ã Andrew Rush, used with permission.

Significance for identification of species. This call is not useful for distinguishing WIFL and ALFL, or, for that matter distinguishing Traill's Flycatchers from several other empids with similar trills in their repertoires.

Distinguishing features. Trill is a series of Pip-like notes that are shorter than individual Pips or Whups. They are sometimes combined with Weeoo. This example is roughly 1 kHz higher in pitch than the example of ALFL Trill in the next figure. I don't know if there is a consistent difference, because I have found no other examples of ALFL Trill. If WIFL Trill is higher, it is surprising, as WIFL Pip and Double-Peak are consistently lower than their ALFL equivalents.

Nomenclature. Stein (1963) used the name "Churr" for series that are characterized mainly by trills, but also include buzzy sounds such as Churr and Weeoo. Sedgwick proposed the name Trill for the series of Pip-like notes and referred to the sounds I call Weeoo (Stein 1963) as "Writ-tu."

Similar sounds. ALFL Trill is indistinguishable. Similar-sounding trills are given by Gray and Hammond's Flycatchers.

Usage. Often with Whup, sometimes with Weeoo.


15.  ALFL Trill
Introduction     Table of Contents     Side-by-side Comparison

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Figure 15. ALFL Trill, 6/13/1993, Denali State Park, Matanuska-Susitna Borough, Alaska. ã D. A. McCallum. This is a low quality recording. Wind was high, and the bird was distant.

Significance for identification of species. This call is not useful for distinguishing WIFL and ALFL, or, for that matter distinguishing Traill's Flycatchers from several other empids with similar trills in their repertoires.

Distinguishing features. Trill is a series of Pip-like notes that are shorter and often lower than individual Pips. They are sometimes combined with Churr notes or other rough sounds.

Nomenclature. Stein (1963) used the name "Churr" for series that were characterized mainly by trills, but also include buzzy sounds such as Churr and Weeoo. With regard to the Willow Flycatcher, Sedgwick (2000) proposed the name "Trill" for series of Pip-like notes and referred to the sounds I call WIFL "Weeoo" ( Stein 1963) as "Writ-tu." I follow Sedgwick in using the name "Trill" for series of Pip-like notes in both species. I continue the usage of "Churr," but limit its application to the buzzy, frequency-modulated sounds presented by Stein (1963) in his Figure 6.

Similar sounds. WIFL Trill is indistinguishable. Similar-sounding trills are given by Gray and Hammond's Flycatchers.

Usage. Often with Weeoo or Churr (q.v.)


16.  ALFL Pip
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Figure 16. ALFL Pip, 8/1/1956, Cutler, Washington County, Maine. Borror Laboratory of Bioacoustics Cut 2226. ã Borror Laboratory of Bioacoustics, used with permission.

Significance for identification of species. Most field guides state that the call note of ALFL is "pip" and that of WIFL is "whit," and at least imply that these call notes are diagnostic. WIFL Whit definitively rules out Alder Flycatcher, but the reverse is not true for this sound, because WIFL has the very similar Whup. Although the two differ quantitatively, on the sparse evidence that is available, it would take a hard-to-assemble large sample of WIFL Whups to provide the backing for identifying an out-of-range ALFL on Pip alone. Fortunately, almost all other sounds of ALFL are diagnostic.

Distinguishing features. Symmetrical rising and falling arms. Higher and briefer than WIFL Whup.

Similar sounds. WIFL Whup (=Pip): Usually shorter in duration and lower in frequency, about 1 kHz in example shown here. Also, even the most Pip-like examples of the quite variable WIFL Whup tend to display the asymmetric pitch trend. Pip of Hammond's Flycatcher is quite similar. The ranges of Alder and Hammond's Flycatchers overlap extensively in Alaska.

Usage. Commonly with Weeoo, yielding a sound that has been likened to WIFL Fitzbew (Stein 1963). Interposed in Trills, which are essentially strings of shortened Pips.


17.  WIFL Pip
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Figure 17. WIFL Whup (Pip), 6/6/2007, Princeton, British Columbia. ã Andrew Rush, used with permission.

Significance for identification of species. Not very useful, because of similarity to ALFL Pip. The existence of this sound in the WIFL repertoire is not widely appreciated. Like Double-Peak, it is rare.

Distinguishing features and nomenclature. Stein (1963) called this call "Pit." First, I change his "Pit" to "Pip" (see ALFL Pip), because one of the few generalities about human transliteration of bird sounds is that most birders hear an up-down chevron as ending in "p," while hearing an ascending trace (see WIFL Whit) as ending in "t." Sedgwick (2000) changed Stein's "Pit" to "Whup," for WIFL. I follow that decision, because ALFL Pip and this sound really do sound a little different, if one is paying attention. I think the aural difference is due more to the difference in duration than to the difference in pitch. I would be less inclined to go with Sedgwick's name change if all Whups were like this one. They are not. Many are higher in pitch, more drawn out in duration, and less symmetrical. It is really a stretch to call those sounds "Pip." Finally, the more extreme examples of Whup grade into Whit by dropping all or most of the descending part. It seems likely that the Whup-Whit complex of WIFL is homologous with Pip of ALFL. It is interesting that the examples that sound and look most like ALFL Pip are so rare. Possibly the ancestral Pip-like form has become vestigial, replaced by the divergent Whit.

Similar sounds. ALFL Pip: More symmetric, shorter in duration, and higher in pitch than this sound.

Usage. With Trill and Churr in indeterminate series. Trills are essentially series of short Pips.


18.  WIFL Whup
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Figure 18. WIFL Whup, 7/18/2004, Izaak Walton Road, near Eugene, Lane County, Oregon. ã D. A. McCallum.

Significance for identification of species. This is a distinctive sound, and should serve to distinguish Willow Flycatcher from all other empids except the two "Pippers," Alder and Hammond's. On present evidence, most Whups are longer in duration and more asymmetrical than Alder Pip, but some examples of WIFL Whup are probably too close to call, making it somewhat problematic to identify out-of-range Alders on the basis of Pip alone.

Distinguishing features. Asymmetric pitch trend, peak frequency around 4 kHz.

Similar sounds. The more drawn-out Whups, like this one, are longer than the Pips of Alder and Hammond's. Duration plus the asymmetric pitch trend give Whup a distinctive aural quality that distinguishes it from most other empid sounds. Acadian Flycatcher call note: similar in form but reaches 6 kHz.

Usage. Often given repeatedly by a rather excited bird, perhaps defending territory or nest from a potential predator. May be interchangeable with Whit, which is used similarly.


19.  WIFL Whit
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Figure 19. WIFL Whit, 8/2/2007, Izaak Walton Road, near Eugene, Lane County, Oregon. ã D. A. McCallum

Significance for identification of species. When the bird has been visually identified as Traill's Flycatcher, the use of dry Whits like this one would, on present knowledge, verify that it is a Willow Flycatcher. Whups are more problematic, because they grade into Pip-like sounds that could be made by an Alder Flycatcher.

Distinguishing features. It is not clear whether Whit is a distinct call from Whup. Most Whits approach 6 kHz in frequency, like this one, and most Whups peak below 5 kHz, like the one in the preceding figure. Some Whits do have a partial descending arm, however, so it is possible that the extremes pictured here are part of a continuum, and that individuals simply vary in the form of their Whup/Pip. Longitudinal study of known individuals is needed to sort these possibilities out. Kaufman (1990:206) wrote, "The Whit of Willow gives the illusion of a slight rising inflection, and it seems to have the hardest or most emphasized sound at the end." It's not illusion; Kaufman correctly perceived the rising pitch trend of this sound, despite its lasting only 1/20 of a second. Many onomatopoeic renderings of bird sounds are problematic, but renderings that end with "t" are typically matched by spectrograms that ascend at the end of the note. If the spectral contour turns down beyond the peak, the sound is "softened" or "thickened," and if the descending arm matches the ascending arm in pitch change, the sound is usually transliterated with a terminal "p," as in "Pip" and "Whup".

Similar sounds. Alder Flycatcher has no Whit in its repertoire. Very similar to Whit notes of Least, Dusky, Gray, and Buff-breasted Flycatchers. "Thicker" and more robust than all of those. Having a partial descending arm makes a WIFL Whit even more distinctive, as this feature is found in none of the Whits of other species.

Usage. Mild alarm and perhaps nest or territorial defense. Both members of pair may Whit, or one may Whit while the other gives Weeoo or Zweeoo.


20.  ALFL Double-Peak
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Figure 20. ALFL Double-Peak, 7/26/2006, Black Balsam (Mountain), 5803 feet elevation, Haywood County, North Carolina. ã D. A. McCallum.

Significance for identification of species. A distinctive sound that is highly characteristic of this species, but is not diagnostic because of the existence of a rarely-heard homologue in the Willow Flycatcher. On present knowledge, Double-Peak calls of the two species are probably distinguishable spectrographically, and aurally-gifted observers may be able to distinguish them in the field, but listen for other calls of either species.

Distinguishing features. Double-Peak is essentially two Pips basted together, or perhaps a Pip and a Pip-like combining form that is the initial feature of ALFL Weeoo. The first peak is typically about 45 milliseconds in duration, like ALFL Pip; the second peak is typically twice that duration, like the single peak at the beginning of ALFL Weeoo. Variation among individuals is substantial, and some individuals may be distinguishable by ear.

Nomenclature. The name "Double-Peak" was coined by Stein (1963). While spectrographically descriptive, it is inconsistent with the wide use of onomatopoeia in sound-names. It is based on spectrographic pitch trend. In as much as pitch trend is audible in this call-type, the name is a satisfactory descriptor.

Similar sounds. WIFL Double-Peak: Lower in pitch, but otherwise similar, and rare, whereas ALFL Double-Peak is used commonly, and sometimes used for singing (see below). In the two examples I've seen, WIFL Double-Peak begins at the top of the first peak, which should be audible in the field.

Usage. Frequently combined with Weeoo and Churr into a stereotyped combination that has been recorded independently by three recordists in Maine. With Churr in North Carolina (pers. obs.). It is also combined with Feebeeo in bouts of singing (Stein 1963, McCallum, pers. obs.).


21.  WIFL Double-Peak
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Figure 21. WIFL Double-Peak, 6/6/2007, Princeton, British Columbia. ã Andrew Rush.

Significance for identification of species. A rarely-heard sound from Willow Flycatchers, but the homologue is commonly used by Alder Flycatchers. For auditors familiar with the Alder Flycatcher, this sound may be misleading or confusing. Those not familiar with the sister species are also likely to be confused, because they likely have never heard this sound. I have never heard it in the wild. I know of two recordings, one from BC, presented here courtesy of Andrew Rush, and one from the Southwestern Willow Flycatcher. This WIFL call- type is not presented in any published sound collection that I know of, but it was mentioned by Stein (1963) and is represented on a training CD for Southwestern Willow Flycatcher workers provided by Mark Sogge of the USGS.

Distinguishing features. Essentially two Whups basted together. The first Whup may be incomplete, often starting, in the two examples I have seen (one from Southwestern Willow Flycatcher, E. t. extimus, one from British Columbia and hence probably brewsteri), near the peak. Note the presence here of a very loud harmonic, which is not obvious in the example of ALFL Double-Peak. ALFL Double-Peaks often do not have loud harmonics. Considering that harmonics in bird vocalizations have to be "intentionally" filtered out, the absence of a harmonic in ALFL may be an evolved isolating mechanism.

Similar sounds. ALFL Double-Peak: Higher, but other field marks should be sought to confirm identification. Hammond's Flycatcher has an infrequently- heard call, Whezee, which is spectrographically similar. As Hammond's and the Traill's complex are in different clades of Empidonax, these similarities are probably convergent rather than being homologous.

Usage. With Trill, Whup, and songs in the source tape for this sample.


22.  ALFL Pip-Weeoo
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Figure 22. ALFL Pip and Weeoo, 7/28/06, Black Balsam (mountain), Haywood County, NC. ã D. A. McCallum.

Significance for identification of species. Has the potential to confuse. If not seen, the bird may not be recognized as in the Traill's Complex, and the observer could spend time trying to shoe-horn the Weeoo into the repertoires of another empid. Moreover, as this combination sounds similar to WIFL Fitzbew, it could lead to misidentification of an Alder as a Willow, particularly where the former is not expected. For those familiar with the call repertoires of both species, it should cause no problem.

Distinguishing features. Note differences between ALFL Pip and WIFL Pip, likewise for Weeoo. For distinguishing this combination from WIFL Fitzbew, focus on the Pip, which is more musical that the "Fitz" phrase.

Similar sounds. WIFL Fitzbew, WIFL Whit-Weeoo.


23.  WIFL Whit-Weeoo
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Figure 23. WIFL Whit and Weeoo, 7/09/2006, Upper Nutria, McKinley County, New Mexico. ã D. A. McCallum. These are two independent calls, which are sometimes combined. In this case, they could have been made by different birds, as two birds were present, but this combination is common (Sedgwick 2000), and his Figure 2e shows the two with equal amplitude, more likely made by the same bird.

Significance for identification of species. Has the potential to confuse. If not seen, the bird may not be recognized as in the Traill's Complex, and the observer could spend time trying to shoe-horn the Weeoo into the repertoires of another of the "whitting" empids (i.e., Least, Dusky, Gray, Buff-breasted) (pers. obs.). For those familiar with Traill's call notes (Whit, Whup, Pip), the Whit portion should keep them out of trouble.

Distinguishing features. The Weeoo is spectrographically, and aurally (with practice) distinct from ALFL Weeoo.

Similar sounds. ALFL Pip-Weeoo: has a Pip not a Whit, and its Weeoo is cleaner. WIFL Fitzbew: has two introductory clicks instead of one, longer in duration.


24.  ALFL Complex Call
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Figure 24. ALFL complex call, 8/1/1956, Cutler, Washington County, Maine. Borror Laboratory of Bioacoustics Cut 2226. ã Borror Laboratory of Bioacoustics, used with permission. This sample is the source of the Weeoo in Figure 8.

Significance for identification of species. Combinations that include several copies of Churr and end with Double-Peak, like this one, are fairly common for ALFL. This particularly variant, Weeoo - Churr - Churr - Double-Peak, has been recorded by three different recordists, in Maine, in different decades. Double-Peak is a much rarer call for WIFL, although combinations of Churr and/or Weeoo do occur in that species. At any rate, determine the identity of the species by the features of the components, not by the pattern of combination.

Distinguishing features. Of the 3 call types above, Weeoo is the most diagnostic for indentifying ALFL. Churr is not helpful, and Double-Peak differs only quantitatively between the species.


25.  ALFL Twitter
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Figure 25. ALFL variable twitter, 6/13/1993, Denali State Park, Matanuska- Susitna Borough, Alaska. ã D. A. McCallum.

Significance for identification of species. Probably not useful, both because it is not a stereotyped call, and because of similar calls by WIFL.

Distinguishing features. Variable structure of notes. ALFL gives a variety of unstructured utterances of this sort.

Similar sounds. WIFL undescribed descending twitter.


26.  WIFL Twitter
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Figure 26. WIFL variable twitter, 7/01/2007, Hooper Lane, near Hendersonville, Henderson County, North Carolina. ã D. A. McCallum.

Significance for identification of species. Probably not useful, both because it is not a stereotyped call, and because of similar calls by ALFL.

Distinguishing features. Variable structure of notes. WIFL gives a variety of unstructured utterances of this sort.

Similar sounds. ALFL undescribed descending twitter. The third and fourth notes in this example are clearly related to "Fitz" of Fitzbew.



All recordings presented here are the property of the recordists and are used here with the permission of the copyright holder. The name of the copyright holder appears above each spectrogram.
Spectrograms, text, design, and source code are the property of AppliedBioacoustics. 2006-2008 AppliedBioacoustics.