Meadowlark “bzerts”: identifiable?

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.

Bzert

Here are four similar calls from Lilian’s Meadowlark, from four different individuals:

Lilian's Meadowlark "bzert" calls.  First by Nathan Pieplow, Willcox, AZ, 5/17/2009 (15-16).  Last three by Andrew Spencer, near Sonoita, AZ, 6/2/2009.

Lilian's Meadowlark "bzert" calls. First by Nathan Pieplow, Willcox, AZ, 5/17/2009 (15-16). Last three by Andrew Spencer, near Sonoita, AZ, 6/2/2009.

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And four similar calls from Eastern, also from four different individuals:

Eastern Meadowlark "bzert" calls.  First, second and fourth from Osage County, OK, March 2006 and 2008 (10-66, 06-04, 10-30); third from Larimer County, CO, 5/31/2007 (21-02).

Eastern Meadowlark "bzert" calls. First, second and fourth from Osage County, OK, March 2006 and 2008 (10-66, 06-04, 10-30); third from Larimer County, CO, 5/31/2007 (21-02).

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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.

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