Comparison of Homologous Sounds
Using This Page

The frames above and below present the five major sounds of E. occidentalis hellmayri (above), the U.S.-Canadian population of the Cordilleran Flycatcher (COFL), and E. d. difficilis (below), the mainland population of the Pacific-slope Flycatcher (PSFL). The COFL sounds are from Colorado, New Mexico, and Arizona, far from the nearest breeding population of PSFL. The PSFL sounds are from coastal and near-coastal populations in California, Oregon, and British Columbia. These samples therefore should be representative of the "core" populations of these species, which are least likely to have experienced gene flow from the other species. In other words, if there are consistent differences between the vocalizations of the two species, they should be evident in these samples. In my opinion, such differences are evident in these reference samples, but this presentation allows you to judge for yourself. For each species there is a panel with all five sounds, then other panels that show several side-by-side examples of each sound. You can navigate independently in each panel (frame). Links are provided for moving within frames. Clicking the "Back" or "Forward" button will also retrieve specific frames.

The distinctive features of these sounds are more evident visually, on the spectrograms, than they are aurally. Click Characteristics of Sounds for a table that points out these features. You may listen to each sound by clicking its spectrogram. Some of the sounds are a bit scratchy. I decided it was important to show the variation visually, even if the sound itself was not of high quality. Most were digitally filtered to make the spectrogram as clear as possible, but this gives the playback a hollow sound. At a later date I will include some more listenable cuts on this site.

After familiarizing yourself with the standards, try viewing and listening to some of the samples from the great "in-between" area, where the specific identity of the Western Flycatchers has been questioned. Each panel is specific to a single pair (i.e., location), unlike the reference panels at top and bottom. Some males do not have a complete sample of all four "male" sounds. Many territories are not represented by a Female Position Note "FPN". Access the list of "Western Flycatcher" (WEFL) samples by clicking List of Geographic Samples. The list gives field notes on each territory, i.e., a presumed male, and/or presumed female found in a specific location, and links to a frame containing its (their) sounds. That frame will appear in the middle of the page, in place of this text, and you will be able to navigate directly to other samples with "previous" and next" links.

Interpretation of Variation

It could be that a population is quite variable but that each individual is clearly referable to one standard or the other. That would argue for the side-by-side occurrence of both species, i.e., the vaunted "Test of Sympatry." On the other hand, individuals may be intermediate between the standards. That would suggest interbreeding, and gene flow between COFL and PSFL. The latter appears to be the case in Deschutes County in central Oregon. Farther south, in the Warner Mountains of Lake County, Oregon, I found less variation among males, and greater similarity to the COFL standards of the southern Rocky Mountains, but the influence of PSFL is still evident. I am launching this site with samples from these two locations. In time I will add samples from elsewhere. I would also like to present here interesting WEFL recordings from other recordists who would like to share their findings with the public. Contact me if you have recordings to share.

I evaluated each sound from the center frame individually by comparing it to the standards presented above and below. My evaluation appears in text below the spectrograms. You will have to scroll down in the center frame to read this text. The URLs for these center frames are "wefl01.html" etc., if you would like to manually open them without the comparative material. Be sure to use lower case for the URL.

This "analysis," admittedly subjective, leads me to the following necessarily tentative conclusions about these sounds (not the birds that made them):

  • Neither the Warner (Lake County) nor the East Cascades (Deschutes County) samples can be allocated unequivocally to the repertoires of one of the nominate species. The Warner sample tends toward COFL and the Deschutes sample is quite intermediate, tending slightly toward PSFL. More
  • Song and MPN are not necessarily consistent in their variation. In some cases, for example, birds that gave nicely-subdivided MPNs had PSFL-like songs. (With respect to this variation, it is possible that sounds ascribed to the same individual were made by more than one bird. Sounds ascribed to one bird were made at the same exact location on the same day, but often not at the same time, and birds were not individually recognizable by sight. Many of the birds were not even seen.)
  • The three song phrases are not necessarily consistent in their variation. One phrase could be ascribable to one of the species while another phrase might be intermediate. (With respect to this variation, it is highly unlikely that more than one bird was involved in any case, as all song samples ascribed to a nominal individual were taken from the same bout of continuous singing.)

    I would like to do a proper multivariate analysis of these sounds. As I don't really have time for that, I invite anyone interested in doing so to download the sounds and have a go at it. I retain copyright to these sounds, and they may not be published as sounds without my written permission. This website is also my property and may not be reproduced without my permission. But, you may publish analyses of these sounds without further permission, although I would appreciate acknowledgment.

    Were I to do a multivariate analysis this is how I would go about it:

  • Let the unit of analysis be the bird or the phrase, not the song. Therefore, unlike Johnson (1980), do not use bout characteristics (e.g., inter-phrase intervals). Because of the inconsistency within samples, it would probably be prudent to conduct four separate analyses (too few samples for FPN) for Phrases 1-3, and MPN, and then build an index from discriminant scores to characterize individual birds.
  • Use the frequency parameters designated herein as being diagnostic. Use intra-phrase temporal parameters similar to Johnson's.
  • Find a way to quantify the curvature of Song Phrase 2. I have some ideas on this.
  • Obviously, restrict the training data set for COFL to the Southern Rocky Mountains and the training set for PSFL to coastal localities, excluding E. d. insulicola.

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