In my last post I talked about how Carolina Chickadee songs have changed (or not) in Columbus and the surrounding areas over the past ~60 years. This post takes a different perspective on how Carolina Chickadee songs can vary: over geographic space. If you were paying close attention in the last post, you may have gotten a sense of geographic variation in song even on a scale as small as Columbus – some songs only appeared in certain areas during certain time periods.
One major component of my dissertation here at OSU has been to quantify how Carolina chickadee songs vary over their entire range, the southeastern United States, and compare this variation to geographic variation in their sister species, the Black-capped Chickadee. Despite Carolina Chickadees being very common birds, not many recordings of their songs were archived in museum collections for me to use. The Borror Lab had the most recordings, but the vast majority of those were made in Ohio.
So in spring of 2014 I embarked on an expedition to record as many Carolina Chickadees in as many different places as possible. Over 5 and a half weeks (divided into three trips), I drove about 6,000 miles through 22 states and recorded over 120 chickadees.
Sample locations during recording trip in 2014
Below are samples of some of the atypical songs that I recorded on my trip. The full Carolina chickadee range is shaded in orange. All the spectrograms shown are on the same scale, so you can directly compare them to one another (the upper limit of each spectrogram image is about 10 kHz). Not included are songs or spectrograms of the typical alternating high-low-high-low Carolina chickadee song, which was also present at most sample locations.
Newark, Delaware
2. Kensington, Maryland
3. Asheboro, North Carolina
4. Cartersville, Georgia
5. Camden, Alabama
6. Ajax, Louisiana
7. Meridian, Texas
8. Moyers, Oklahoma
9. Crossville, Tennessee
10. Salem, Missouri
11. Makanda, Illinois
12. Mammoth Cave, Kentucky
About the author:Stephanie Wright Nelson is a graduate student in the department of EEOBiology. She studies song learning in chickadees and is particularly interested in the consequences of hybridization between Carolina and Black-capped Chickadees.
One thing that is unique about the sound archive of the Borror Laboratory of Bioacoustics is that it not only contains a wide diversity of animal sounds, but a great number of recordings for certain species. When I started my Ph.D. research here at OSU, I was pleasantly surprised to find that this depth of recordings also included one of my study species, the Carolina Chickadee (Poecile carolinensis).
The namesake of the Borror Laboratory of Bioacoustics (BLB), Dr. Donald J. Borror, was one of the first biologists to take recording equipment out into the field to record animal sounds. And he started in and around Columbus. Because Carolina Chickadees are rather common birds here in the central and southern portions of Ohio, Carolina Chickadees were some of the first animals Dr. Borror recorded. The oldest recording he archived in the collection dates back to 1948. Listen to a 30-second excerpt of Dr. Borror’s recording of a typical four-note whistled Carolina Chickadee song from April 1948 (note: You can listen to the entire recording (BLB21) on the BLB’s website):
You may not think that having all these chickadee recordings across a long time period is super duper exciting, but I do. See, I study chickadee song. And we know that chickadees, like other songbirds, learn their song: young chickadees must hear other individuals of their species singing and imitate those sounds in order to produce normal adult song. However, like learning in humans, song learning in birds is not always a perfect process. As young birds make imperfect copies of the songs of the adult birds they hear, variation is introduced into the songs of a population of birds. Think about how the English language has changed in the past 100 years – some words have stopped being used, new ones have come into fashion – this is analogous to what happens with song in bird populations.
The end result is that not every chickadee sings exactly the same song and the acoustic traits of chickadee songs can change slightly from generation to generation. Using the BLB collection I can actually look at how Carolina Chickadee song has changed in the Columbus area over the past 65+ years.
What you are going to see below are a series of maps with representative spectrograms of chickadee songs from all over Columbus for different decade ranges. If you have never seen a spectrogram before, it is essentially a visual representation of sound, with time on the x-axis, frequency (or pitch) on the y-axis, and the darker color representing more energy (or the loudness) of the sound. Here is the spectrogram of one song of a Carolina Chickadee from the 1948 recording by Don Borror above:
For each map below I encourage you to visually compare the different chickadee songs using the spectrograms (I have left the axes off for simplicity’s sake) and then listen to the recording containing those songs using the links below each map. Any overlapping spectrograms are from the same individual bird: Carolina Chickadees can sing up to 4 different song types each, although most only sing one or two types. If you want to listen to the original recording archived in the BLB, please click on the link for each BLB cut number.
1950s
As you can see, Carolina Chickadees usually have a four-note song of alternating high and low whistled notes, but check out the weird song at Blacklick Woods Metro Park (#3)! Dr. Borror’s 1948 recording is actually quite unique in that the notes in the chickadee’s song are not very different in pitch from one another; usually Carolina Chickadee songs sound and look more like the spectrograms seen in examples 1 and 4b.
The unique song type seen before persists at Blacklick Woods Metro Park through the 1960s. Also note that some Carolina Chickadee songs start with a note much lower in pitch than others (like song number 1 here, or song 4a in the 1950s map). Carolina Chickadees also sometimes add notes onto the end of their songs, resulting in five-, six-, and sometimes up to twelve-note songs, although they usually keep the alternating high-low pattern (see #4).
Many of the songs in this decade are very similar, but one individual at Blendon Woods Metro Park (#2b) showed an interesting song with an additional introductory note. This song type is not seen in any other bird in any other decade, so it is possible this song type was never sung by any bird but this one.
As you can see, not much song variation was recorded in the 1980s, except for that three-note song up in Delware. While most of the songs follow the typical high-low-high-low pattern, there are subtle differences between individuals, like in the downward sweep of the first note.
In Delaware a three-note song type persists in the population from the 1980s into the 1990s. Also, the song type that starts with a lower-pitched note continues to pop up in various areas of northern Columbus (e.g. 3b), but is not seen in the southern portions of the city. Interestingly, I had not heard that song type myself while living in Columbus until moving to Clintonville this past March; up near Dublin that song type is not common anymore.
In the past 14 years none of the recordings in the BLB collection specifically target Carolina chickadee songs. It would be interesting to know if those strange songs from Blacklick Woods Metro Park are still sung in that area, or if any other unique song types have appeared in the Columbus area.
So, as you travel throughout the Columbus area, keep an ear out for some odd chickadee songs … you may even hear something that has not been recorded before.
About the author:Stephanie Wright Nelson is a graduate student in the department of EEOBiology. She studies song learning in chickadees and is particularly interested in the consequences of hybridization between Carolina and Black-capped Chickadees.
