I’ve just posted the first part of my online tutorial on how to read spectrograms. Lesson One deals with Pitch and Inflection. More lessons to follow; all will be permanently available through the menu bar.
Let me know what you think!
Today Matt Young told me about David Sibley’s recent post on vocal mimicry in Pine Siskins. The surprise to me (and to Sibley and others) was not that Pine Siskins infringe on other birds’ copyrights, but rather that this fact had gone unreported in the literature for so long. Actually it hadn’t just gone unreported; it had been refuted. For example, the Birds of North America account on Lesser Goldfinch says:
Mimicry of other species in [Lesser Goldfinch’s] song repertoire, first documented by Dawson (1923), is a characteristic shared with Lawrence’s, but not with Pine Siskins or American Goldfinches. (Other cardueline species known to display interspecific mimicry are Purple Finch [Carduelis purpureus], Cassin’s Finch [Carpodacus cassinii], and Greenfinch [Carduelis chloris; Guttinger 1977]).
In addition to the above species, the Pine Grosbeak is an excellent and frequent mimic (Adkisson 1999). Mimicry has also been documented in House Finches (Sewall & Hahn 2003), although apparently only once, in an anomalous bird.
Evening Grosbeaks and the three rosy-finches are members of the Carduelinae, but they don’t sing complex songs as their relatives do; in all four of these species it’s likely that long series of call notes serve the basic functions of song. Interestingly, although several early authors reported that Evening Grosbeaks and Black Rosy-Finches sing soft warbling or twittering songs, modern authors typically do not mention them, and sound recordings of these musical “songs” are rare or nonexistent. Perhaps the early authors were handicapped by a basic conviction that all songbirds must have a song.
The remaining North American Cardueline finches (redpolls and crossbills) have not been reported to mimic other species, although I’d be surprised if the Red Crossbill, at least, never mimicked, as its song is so tremendously variable. I find it fascinating that some species mimic while their close relatives do not. Why do Lesser and Lawrence’s Goldfinches mimic, but not American? Why do Cassin’s and Purple Finches mimic, but not House Finch (usually)? Perhaps House Finch and American Goldfinch are mimics, but such poor ones that we don’t recognize their attempts as mimicry?
What do you think? Any reports of mimicry out there that haven’t made it into the literature?
In the middle of the afternoon a few weeks ago I was sitting in the public library in Sierra Vista, Arizona–a wonderful facility, by the way–escaping the heat of the day to download my bird sound recordings, recharge my batteries, and check my email, when my attention was drawn to a bird hopping directly toward me on the ground. No, it wasn’t in the library–it was on the other side of the floor-to-ceiling plate-glass windows, out in the desert garden. But it might as well have been in the library, because it ended up hopping right up to the window, less than four feet from my face, so that even without binoculars I could clearly see its pale yellow eye, its short, almost straight bill, its nearly-unmarked breast with a few spots front and center…in short, every field mark necessary to confirm its identity as a Bendire’s Thrasher–a scarce species I had seen only three times before.
And then, through the window, I heard it begin to call: a slightly noisy, one-syllabled note reminiscent of the “cheep” call of the American Robin. Naturally, I raced right out to record it:
The call note clinched the ID. It was completely different from the characteristic call of the very similar-looking Curve-billed Thrasher, the loud wit-weet! that is a trademark sound of the southwestern deserts:
I was particularly excited to record the Bendire’s because their one-syllabled call note had been described in the literature, but as far as I could tell, never recorded — I didn’t know of any commercially available recordings that included it, nor had I ever seen published spectrograms of it. The Macaulay Library didn’t have it, and in the two different mornings I’d spent recording Bendire’s Thrasher in Arizona and California, I’d never even heard it, much less caught it on tape. So I was pretty stoked.
I relayed the details of my sighting to my friend Andrew Spencer, who was due to arrive in southeast Arizona shortly after I returned to Colorado. He was equally excited about this rare recording opportunity, and he made a point of stopping at the Sierra Vista Public Library as well. That morning I got a message from him that relayed some good news and some bad news. The good news: he’d found the bird right where I said it would be, acting just as I’d said it would, giving calls just like the ones I’d recorded. The bad news? It had been accompanied by, and fed by, two adult Curve-billed Thrashers. It wasn’t a Bendire’s at all–it was just a juvenile Curve-billed.
Sure enough, when I went to look at the Bendire’s Thrasher chapter in Kenn Kaufmann’s Advanced Birding, there was the description of a juvenile Curve-billed Thrasher, matching my bird to a T. I had forgotten that Bendire’s has a pale base to the lower mandible, which my bird had lacked. And Kaufmann even mentions the single-syllabled call note of the juvenile Curve-billed. Blast.
The morals of this story:
I wanted to follow up on my last ID post with an exploration of call notes in Lilian’s and Eastern Meadowlarks. Since meadowlarks learn their songs but not their calls (i.e., their calls are genetically determined), in theory, any significant differences between their calls might provide evidence that they should be split at the species level. Cassell (2002) didn’t analyze calls; the Birds of North America account claims that Lilian’s and Eastern calls are similar. And indeed they are–but there might be some perceptible differences too, as we shall see.
Caveats will abound in this post, and here’s the first one: meadowlark calls appear to be variable both geographically and within individuals. All meadowlarks make a number of different sounds, and some of those sounds grade into one another occasionally. Thus, I’m not certain that all of the sounds I’ve grouped together necessarily belong together in a biological sense–but they do sound similar.
I want to look at a number of different kinds of calls eventually, but today I’ll have time for only one: the bzert.
Here are four similar calls from Lilian’s Meadowlark, from four different individuals:
And four similar calls from Eastern, also from four different individuals:
I think I both hear and see a difference there, don’t you? Lilian’s tends to be briefer, more clipped, while Eastern seems to be more drawn-out. If I was confident the above samples were representative of the population as a whole, I’d go ahead and declare these taxa identifiable by call. Unfortunately, some of the recordings in the Macaulay Library complicate the picture. The Lilian’s bzerts on Catalog #56852 are similar to the ones I’ve posted, but those on #20853 and #174 are a little longer. Macaulay’s Eastern bzerts, meanwhile, are all over the map. Catalog #12680 has a number of different-sounding versions of the call, including both upslurred and downslurred versions. #105634 has a number of short ones, much like the Lilian’s I posted. #12699 features several renditions of a bizarre two-syllabled version. Go check these out.
In short, the differences in the samples I’ve posted are tantalizing, but I’m not sure how much to trust them. Larger sample sizes, particularly of Lilian’s, would be helpful in sorting all this out. A systematic and statistical analysis is probably called for in the long run, but in the meantime, listen carefully to your local meadowlarks and make some recordings if you have the wherewithal. One thing is clear: any differences between the bzert calls of these two taxa is pretty slight overall. They are closely related organisms, for sure.
My friend Walter just sent me a link to Paul Driver’s excellent bird song blog. I searched the web for other bird song blogs before I started mine, but I certainly missed this one! According to his brief bio on Xeno-Canto, Paul is British by origin but now lives in the Philadelphia area. I highly recommend a visit to his site–he’s only been posting for six months, but he’s already amassed a terrific collection of bird sounds, with spectrograms, audio, and commentary on each. I am particularly impressed by his focus on little-known vocalizations, including flight calls, begging calls, alarm calls, and the like. I mean, he’s got five different calls of Gray Catbird up right now (with multiple examples of a couple of those): that’s far better than XC at the moment! Alas, no crossbills.
Keep up the good work, Paul!
Interest in “Lilian’s” Meadowlark has spiked with the publication of Barker et al. (2008), which found significant genetic differences between Lilian’s and other “Eastern” Meadowlarks and recommended that Lilian’s be elevated to species status. Naturally, I keyed right in on the following quote:
Cassell (2002) found significant differences in the songs of Eastern and Lilian’s meadowlarks. However, given the learned nature of song in this group (Lanyon 1957), and the sharing of unlearned call notes between these forms (Lanyon 1957, 1962), the relevance of this observation with regard to species limits remains an open question.
A couple of months back I ordered Cassell’s (2002) thesis through interlibrary loan, to judge the evidence for myself. Overall, I found some aspects of the work very useful, but other aspects quite questionable. In particular, I have two complaints:
Despite these issues, Cassell does convince me that Lilian’s songs average significantly lower in frequency than Eastern songs, in agreement with the descriptions in Sibley’s field guide. Cassell says:
In the field, the astute listener may recognize the primary song of S. m. lilianae by its overall lower pitch than that of S. m. magna.
So far, my experience indicates that this statement holds true in most (but not all) cases. Lilian’s song is frequently, but not always, low-pitched enough that it sounds like Western Meadowlark in tone quality (although the pattern of each song is still much more like Eastern than Western). In addition, it seems to me that Eastern Meadowlarks frequently end on a drawn-out, nearly monotone clear whistle, while Lilian’s tend to end on a whistle that is much more downslurred. There is a lot of overlap in the final note type, so caution is warranted, but I think the combination of terminal inflection and, especially, overall pitch (perceived largely as tone quality) should identify most Lilian’s Meadowlark songs.
A few weeks ago in Arizona I was able to record a few Lilian’s Meadowlark songs:
The first songtype, with its low pitch and its complex middle section, is particularly reminiscent of Western Meadowlark, but all three above seem fairly typical of Lilian’s. Note the downslurred endings.
For comparison, here are three typical songs of Eastern Meadowlark. Note the more “ringing” monotone endings (characterized by more horizontal lines on the spectrogram) and the relatively high pitch (lowest frequencies about 3 kHz, as opposed to 2 kHz for Lilian’s):
If all songs of both forms fit these patterns, field identification would be pretty easy, but sometimes the birds will throw you for a loop. Here’s a Lilian’s that sounds more like an Eastern on account of its high pitch and monotone ending:
And here’s a Eastern that sounds something like a Lilian’s on account of its relatively low pitch:
And, of course, not all Easterns have the ringing monotone ending:
For a little more ear practice, check out this wonderful repertoire remix of 19 different Lilian’s Meadowlark songtypes, all recorded by Andrew Spencer on 6/1/2009 from one individual bird in Eddy County, New Mexico. You’ll notice that about half the songtypes end in a ringing monotone whistle, which seems to be a slightly higher percentage than among the birds I recorded in Arizona.
To hear more Eastern Meadowlarks, check out Xeno-Canto’s collection. The Macaulay Library has plenty of Eastern Meadowlark songs also, and even a few Lilian’s.
All right, let’s find out how well this works. Here’s a remix of three meadowlark songs. Which ones are Eastern and which are Lilian’s? Leave your guesses in the comments field, and I’ll post the answers in a couple of days.
I think most birders know by now that Red Crossbills in North America sort into a number of different call types, each of which may constitute a cryptic species. Identifying these types in the field promises to be a bugaboo of legendary proportions. Where does one begin?
In this post I’ve collected links to some online resources that can get you started: a sort of Crossbill Q & A, if you will.
1) What are the crossbill types? How did they evolve? Are they for real?
A great source for beginning to answer these questions is Craig Benkman’s introduction to crossbill types in the July 2007 issue of Colorado Birds. Although it doesn’t discuss identification, the article’s overview of the research on crossbills is extremely valuable to anyone in North America, in spite of its nominal focus on Colorado.
When you’re ready to dig a little deeper, head to Benkman’s home page and look at the list of publications he has posted in PDF form. The man is a scholarly publication machine. Every important paper on crossbill types that has been published to date can either be downloaded from Benkman’s page or can be found referenced in the bibliographies of one or more of his works.
2) Where can I listen to online recordings of Red Crossbill types?
Your first stop should be Jeff Groth’s old page on the website of the American Museum of Natural History. Although Benkman may be the current guru, Groth was the original discoverer of the call types. The good news is that his page has audio files of the flight calls, excitement calls (“toops”), and alarm calls of types 1-7. This makes it the most comprehensive collection of crossbill vocalizations on the web. It also has range maps and basic natural history information for each of these types.
The bad news is that Groth’s site was, believe it or not, last updated in 1996, back when the Internet was in primary school. Not all of the links still work. There’s only a single audio file for each vocalization, and worst of all, because the files date from those dark days when 50 kB took a long time to download, they’ve been cut so short that they don’t sound like they do in the field–instead they all sound too much like each other. Appreciate Groth’s site for what it has, but don’t let it intimidate you. Crossbill identification is very hard, but it’s not hopeless.
Here are a couple of less comprehensive but more user-friendly resources:
In addition to the resources I’ve mentioned, there’s always the Macaulay Library, which is my favorite collection of online bird sounds. In an upcoming post I’ll try to put together an index to the types heard on the Macaulay recordings.
More on crossbills soon!