Only one study on the vocalizations of Purple Martin has ever been published, by swallow guru Charles Brown in 1984. In that study, Brown compared the sounds of Purple Martins at two sites: one in central Texas, and one at high elevation in the Chiricahua Mountains of southeast Arizona. He reported differences between eastern and western birds in several types of vocalizations, as summarized here:
|Veer Phrases||Almost always include a stereotyped 3-note pattern||“Uttered in variable sequences […] with no pattern”|
|Burrt||Long (0.3 – 0.6 sec), consecutive calls often run together||Short (0.1 – 0.2 sec), consecutive calls usually well separated|
|Day song (male)||Long (2 – 6 sec), with at least 2-3 grating sounds interspersed||Short (1.5 – 3 sec), with grating sounds only at the end, if present|
|Female song||More downslurred syllables than Burrts||More Burrts than downslurred syllables|
Since Brown’s study was conducted at only two sites, I’m curious whether the findings can be generalized across the continent. Do all eastern birds sound like the ones at the site in Texas? Do all western birds sound like the ones at the site in Arizona? Or do Purple Martins show patterns of regional variation all across North America?
Let’s check some of these reported differences against available recordings.
Veer and Veer Phrases
Brown didn’t distinguish between the Veer and the Veer Phrase; he discussed them together under the name “zweet calls.” When he said “zweet calls” of eastern birds tend to be slightly upslurred, I suspect he was referring to Veer Phrases instead of individual Veer calls, because the individual Veer calls are generally downslurred all across the species’ range:
This recording from the southwestern desert (ssp. hesperis) sounds different–shorter, sharper, and less burry.
But not all hesperis sound this way. These sound the same as eastern birds:
So that short, sharp version from Arizona might actually represent something other than the Veer calls — perhaps an intergrade between Veer and Tew calls.
Day Song (male)
In this recording from Tucson (presumably of hesperis, the desert subspecies), the song matches Brown’s description for western birds, with multiple grating sounds throughout the song (only properly heard once, at 0:33):
Same goes for this song from Humboldt County, California (at 0:26):
And this recording from the high Chiricahuas (from 0:45 to the end):
But this recording of hesperis has a single grating sound at the end of each song phrase, like Brown described for eastern birds:
And this recording from California has no grating sounds at all, again like Brown described for eastern birds:
As far as I can tell, same goes for this recording from California: no grating sounds to speak of. If present, they’re at the end.
Here’s a “classic” eastern song that matches Brown’s description, with the grating sound only at the end:
But here’s an eastern bird that regularly includes multiple grating sounds interspersed in its song:
And another (especially from about 1:30 t0 2:10):
So it seems that at least some birds all across the continent give multiple grates in their songs; some birds everywhere give a single grate at the end; and some birds everywhere leave out grates entirely.
Overall, I’m not seeing much support for the idea of systematic vocal differences between eastern and western populations of Purple Martins. There are certainly regional and individual differences, and probably local dialects, as would be expected in almost any bird that learns its song. But I’m always willing to learn more, and if you can enlighten me on this topic, please do!