Friday, March 14, 2014

Chickadee Call-and-Response






It’s March, and time to write about Chickadees again.  They’ve been singing for a little while now, and I just saw a pair starting to investigate possible nest cavities.  (Considering the relentless winter we’ve had, they may have been searching to see if there are any cavities that are not filled with snow.)


You may recall from last spring that I’m interested in learning more about Carolina Chickadee songs, the northward movement of this species into the land of the Black-capped Chickadees, and the songs that hybrid Chickadees sing in the contact zone where the two species overlap.


I’ll do a little bit of chickadee review – you can always skip over the parts you know.



If you live in the northernmost counties of Ohio, you are in Black-capped Chickadee territory.  Their songs are easy to learn:  just two clear pitches a step apart.  The second pitch is usually a step (specifically a major 2nd) lower that the first pitch.  The pitches are slow and clear enough that you can imitate them.  Two notes, a pause, and then repeat.  That’s all there is to it.  The only variation I hear is occasionally just one note of the two-note song, but then the two-note song follows.  That’s about it for the Black-cappeds.  


Here’s the song.  I recorded this one at the Holden Arboretum in Lake County, but you can hear the same song in our Cleveland Heights yard and everywhere else around here.  The pitch may be a little higher or lower, but the song is basically the same.  





According to Donald Stokes in A Guide to Bird Behavior, Black-capped Chickadees sing to establish and defend their nesting territory boundaries but not for the purpose of attracting a mate.  (Stokes, Donald. 1979.  A Guide to Bird Behavior, Vol. 1.  Little, Brown, and Company.)


Birds like the Tufted Titmouse. Northern Cardinal and Song Sparrow have a range of songs and males can challenge each other by switching songs.  The other male would then switch the first male’s song – he’s got to be able to imitate the other song, or he’s not going to impress anyone.


But the Black-capped Chickadee just has those two notes a step apart – what is he going to do with that?


 

He has a bit of a vocal range, though, so he can change the pitch level of his two-note song.  He can sing his song a little higher or a little lower.  He may sing his response above or below the other bird's pitches, or he can choose to exactly match his opponent. Here are two examples.



In the first, the birds are almost at the same pitch:






In the second, Chickadee #2 sings his song an exact whole step lower than Chickadee #1.  It’s as if he takes the lower note of Chickadee #1’s song and goes down a whole step from there.  Or…is it possible that Chickadee #1 takes the higher note of Chickadee #2’s song and goes up a whole step from there?  Which came first – the higher song or the lower song?  




The pitch relationship is very common.  I haven’t been recording these because they are so very widespread – I can even hear this pattern from our front porch.

Which pattern is the more serious confrontation? 


I hadn’t thought about the fact that modifying the pitch level is something rather special until I came across an article called “Matched Counter-singing Signals Escalation of Aggression in Black-capped Chickadees” (Shackleton, S. A. and Ratcliffe, L., 1994, Matched Counter-singing Signals Escalation of Aggression in Black-capped Chickadees. Ethology, 97: 310–316.)  According to Shackleton and Ratcliffe, Black-capped Chickadees don’t match pitches during the dawn chorus (when everyone is singing) but do so as a conflict escalates.  They wrote , “…matched counter-singing was highly associated with escalation of the conflict.  We suggest that frequency matching in this species may be a graded signal that allows the singing to direct aggression toward a particular rival” (p. 310). 

If these Chickadees can’t challenge each other by changing their simple, two-note songs, they can instead challenge each other by changing the pitch!  Exactly matching the pitch of an opponent’s song may indicate a higher degree of conflict escalation that matching songs a step apart.  The composer in me thought that matching the song a step lower or higher might be a more creative and daring response, but my human response may have gotten in the way a bit.


Still, that relationship of two birds singing exactly a whole step apart is so common that I can’t help but wonder if that relationship has some significance as well.  I guess I’ll be recording all the interactions I hear this spring. 


I’ve imitated both versions of the call-and-response – the one that’s on the same pitch and the one that is a step lower.  Black-cappeds will respond to either one, even though I’m probably a rather pitiful competitor.  I don’t do this when they are actually nesting, though, as I never want to stress birds that need to focus on reproduction.  Just keep in mind as you read ahead that this is a bird I can imitate and that will respond to my whistling.


So now let’s move south a bit – we’re heading toward central Ohio.




Carolina Chickadees, which can be found from about Route 30 (Canton-Mansfield-Findley) south, sing a more complex song.  It typically has the two pitches of the Black-capped Chickadee song decorated with two additional higher notes that ornament the song.  Here’s an example:




So what do Carolina Chickadees do when they challenge each other with song?  I’ve gotten a response when I whistled my rendition of a Carolina Chickadee song, but in that case I’m the one who is imitating the bird.   If I’m not sure which species is present, though,  I’ll try my generic version of each species’ song to see if either gets a response.  


But Carolina Chickadees have variations in their song, where the Black-capped do not.  Do they match song types, and also match song types plus pitch levels?  Do they have as flexible a pitch range like their Black-capped cousins?  I’ve heard them match both song type and pitch, but since this species is well south of where I live, I simply don’t have much experience with their songs.


I hope to listen more closely on an overnight trip to Columbus soon, and I’ll report back to you if I hear anything interesting.  Those of you who live in the land of the Carolina Chickadees, please tell me what you’ve observed.


Finally, do you remember those fascinating Black-capped/Carolina hybrid Chickadees I recorded at The Wilderness Center on the southwestern corner of Stark County last spring? 
There are Black-capped, Carolina, and hybrid Chickadees at this location right along the contact zone between the species, and they interbreed.  Hybrid males can sing the songs of either species, but sometimes they sing unique songs that are neither Black-capped nor Carolina.  You can imagine that the composer in me thinks this is quite interesting!  I said I’d plan to go back the following spring. 


I did indeed to back to listen for them earlier this week, hoping I might hear those odd, lovely songs again.  I tried whistling both the Black-capped and the Carolina songs, but no one answered me. I thought I might be hearing one or two Chickadees off in the distance, though, so I whistled one of the hybrid Chickadee songs I'd  heard and recorded last spring.   Here's the song.



A chickadee flew over toward me and began counter-singing with my barely-passable rendition of last year’s hybrid Chickadee song.  This is what he sang – and he matched my whistled pitches.




It was identical to last year’s song.  I was delighted!  Call and response with a hybrid Chickadee?  I can hardly wait for spring to finally triumph in NE Ohio and for more time in the field!  I only wish I could also spend more time with the Carolina Chickadees to learn  their repertoire as well.










4 comments:

  1. That is wonderful Lisa. I really enjoyed listening, there is hope for the rest of us to develope an ear as long as you are around! Enjoy the southernly trip.

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  2. Beautiful photos and how lovely to hear their sound!

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