Along with comments left on my blog (read them here), I received some excellent e-mail and listserv feedback on the Yellowknife Yellow Warbler's story I wrote about last week (click here to read the original story). I wanted to share these comments with you below. Thanks to all who took the time to comment and add to the discussion!
Yellow Warbler
Credit: John Kormendy
Craig Machtans:
I've never spent time in habitats where Chestnut-sided Warblers are around, so the comparison is lost on me. However, I do know that many Ontario folks we hired during my graduate work days in Alberta (Calling Lake area, north of Athabasca) were all CERTAIN that bird they were hearing was a Chestnut-sided Warbler until of course they looked at it and were dumbfounded. That was not an isolated experience for one or two birders - if was kind of a rule. My experience in the Northwest Territories is that most of the Yellow Warblers seem to be similar in songtype (I don't have trouble picking them out anywhere compared to hearing the ones around Yellowknife) and that songtype is pretty close to what I remember from Alberta.
By chance did you pull out the Cornell Songs of the Warblers of North America? The sonogram page in my book has examples lettered from A - R (18 examples) and I see several with decending final notes. 12-O seems at first glance to not be a bad match to your posted sonogram.
Cameron Eckert:
Yes, that does have the overall pattern of Chestnut-sided but the first two notes give it away as Yellow Warbler. There was a crew led by David Green studying Yellow Warblers in Inuvik, NWT this past summer. It would be interesting to hear about what they found in terms of song. I have heard some very local dialects of a variety of species in the north. For example, a hike in 2008 to Grizzly Lake in Tombstone Park of central Yukon found American Robins singing a very distinctive and unusual song.
Fiona Schmiegelow:
I can't comment on the NWT, but about half the Yellow Warblers around Calling Lake, AB, also exhibit this song type. We also have a few Chestnut-sided Warbler records for the area, so one needs to be quite careful with identification.
David Spector, Central Connecticut State University:
I have done some research on Yellow Warbler songs and might be able to address some of the points raised in this discussion.
1) "Meetcha" or "Beecher" or "Wee-chu" or "wolf whistle" endings (i.e., a rising syllable followed by a descending syllable) of Yellow Warbler songs are common and widespread in North America. To my knowledge, no one has ever done a study of geographic variation of the songs of this species across the continent, so I can't address the relative abundance of those endings in different parts of the range. I have the impression that these Chestnut-like endings are uncommon in parts of the Yellow range, particularly in Maine, so someone who learns Yellow songs in such an area is more likely to be surprised in other parts of the Yellow range.
2) Yes, these songs can sound like Chestnut-sided Warbler songs, but attention to the entire song can often provide a distinction. Yellow Warbler songs are typically a bit faster in internal pacing, with a bit more of a sense of acceleration, and a bit higher in frequency distribution (which we perceive as pitch). Conversely, Chestnut-sided Warbler songs typically sound a bit statelier in the relatively even pacing of syllables and a bit lower in pitch. A focus on one feature of a song is like a focus on one visible field mark, subject to more error than is using multiple features. Of course, in a song that lasts a second or so, especially if heard only once, it is often difficult to pay attention to all details. Humans often seem to take some time (maybe a half second) to realize that a warbler is singing, by which time the distinctive ending might be the only thing left.
3) Oscines (everything after New World flycatchers on the checklists) learn songs, so geographic variation is the norm.
4) Both male Yellow Warblers and male Chestnut-sided Warblers have multiple songs in their repertoires:
Each male Yellow Warbler has about a dozen songs in his repertoire. One of those songs is his "Type I" song, which predominates in daytime singing, especially when he is unmated. The rest of his song repertoire, "Type II" songs, is sung in a rapid-fire dawn bout (typically starting about an hour to half hour before sunrise and lasting about a half hour), in territorial interactions with other males, and to some extent at other times, especially after pairing.
Unfortunately, there is no simple distinction, other than how they are used, between Type I and Type II songs. One male's Type I song might be very similar to the Type II song of another male. (This situation is very different than with some other wood-warblers, such as Blue/Golden-wings, or Chestnut-sided Warblers, for which there are clear structural differences between song categories).
Each male Chestnut-sided Warbler typically has a few (around two to four) "Accented Ending" songs, variants on the familiar "pleased pleased pleased to meetcha." (Or "I wish to see Miss Beecher.") Each male also has several (about 4 or so) "Unaccented Ending" songs, which, as the name suggests typically lack that distinctive ending. The Accented Ending songs overwhelmingly dominate daytime singing, with the Unaccented Ending songs used primarily in the dawn bout and in intense territorial encounters. Many people familiar with Chestnut-sided Warblers have seldom heard these songs. To my ear, some of the Unaccented Ending songs can have an Oporornis-like quality. (My ears are not very good, and others with better ears might want to add regarding the identification issues.) Chestnut-sided Warblers sing with extreme eventual variety, i.e., with very rare switching between song types. Thus it is possible to listen to a male for many minutes, even for hours, and hear only one song type. There is much less variation among Chestnut-sided Warbler songs, especially the Accented Ending songs, than among Yellow Warbler songs.
5) I've gone on rather long (easy to do on one of my favorite subjects--thanks to Allison and Jeff for bringing up this most interesting topic!). Those who want more detail can consult the Birds of North America accounts (I'm a co-author on the Yellow Warbler) and references therein. Anyone who wants all the little exceptions, asterisks, additions, maybes, etc., to my comments above, just ask.
More from David Spector: My comment about those Chestnut-like endings being rare for Yellow songs in Maine is based on my memory of Doug Morse's classic work on Yellow Song (done largely at Damariscotta, if I remember correctly). It's been a long time since I read his articles, but I seem to recall that there was little if any mention of those endings, suggesting that they were not common. It is conceivable (and intriguing if true) that the Chestnut-like endings are more common in Yellow songs where Chestnut-sided Warblers are rare or uncommon—a project for someone with a lot of spare time and a recorder.
Jim Hengeveld:
Yellow Warbler songs that sound like Chestnut-sided Warbler songs are fairly common among breeding Yellow Warblers in the Bloomington, Indiana (south-central Indiana) area. It seems like I've heard a greater frequency of such songs later in the season but I'm not positive. I'll have to pay closer attention to that.
James Remsen:
Haven't had field experience with these Yellows that sound like
Chestnut-sideds, but I've got a bird song record or CD (or two or three)
with this variation on it somewhere. We're talking decades-old
recordings, so this variation has certainly been documented.
Yellow Warblers in the Caribbean really gave me fits the first time I
heard one. I thought I had found some obscure tropical warbler, only to
track it down and find it was not.
And then there was the Black-throated Blue I found singing a weird,
sizzling buzz that was almost a dead ringer for a Cerulean. This was on
a Birdathon, so you can imagine my displeasure at tracking the bird down
and discovering there would be no Cerulean on my list that year after
all.
Marcel Gahbauer:
I've experienced similar surprises with Yellow Warblers in northeastern Quebec and Labrador. American Redstarts also are part of the mix there, not necessarily sounding like they "usually" do either. But then there's no shortage of species with substantial geographic variation in song ...
Dark-eyed Juncos in some areas sound an awful lot more like Chipping Sparrows than they do elsewhere, some of the Cape May Warblers in the east seem to have a double-toned note, and Ruby-crowned Kinglets in the western / central / eastern part of the boreal differ substantially. And these are just the first ones that come to mind!
Marcel Darveau:
I am not a specialist of bird song variations, but when I listen to your Yellowknife "pseudo-chestnut-sided" warbler, it sounds like Quebec yellows during midday. I have been living at the same place for 25 years and I have a yellow nesting around each year. They often sing the typical "yellow" song early in the morning and the other the midday.
