Sometimes even the expert (me!) gets confused, about things that I am supposedly quite familiar with. Such was the case in the summer of 2007 during a visit with friends in the the hills south of Corvallis, Oregon.
I got up early one morning and went in search of an immature Cooper’s Hawk which one of my friends had heard the day before near the top of a hill. As I approached the spot, my attention was drawn to a vireo of some sort (or so I thought), singing phrase after phrase from the top of a fir tree. Not being that familiar with western vireos, I was not sure which species I was listening to. Within seconds, I heard a Cooper’s Hawk give several whining screams from nearby. My mind, which was a bit groggy from lack of sleep, started putting things together, but failed to grasp the full import of the situation.
A little voice inside told me that the “singing” was a response to the presence of the hawk. But what the voice failed to inform me was that I wasn’t hearing a vireo at all … I was actually hearing the so-called “vireo song” of a Purple Finch (which I was already familiar with and which I firmly believe is given in response to aerial predators, based on observations of finches back home in New York). My mistake is evident when you hear me comment on the recording, but notice that I caught my error before I finished talking:
Purple Finch responding with ‘vireo-song’ in the presence of a Cooper’s Hawk. 7:30am, 8 July 2007, near Corvallis, Oregon. Recorded by Lang Elliott.
The “vireo song” of the Purple Finch is fairly well-known, although in reality it is not really a “song.” It was described by Aretas A. Saunders about 75 years ago, and he correctly noted that the sound sequence was similar to the song of a vireo. But Aretas and virtually everyone who has followed never made the connection to aerial predators (at least I don’t think anybody has). Then I come along and observe three cases of the vocalization being given by Purple Finches in the presence of hawks.
Granted, a sample size of three is not much, but the mere fact that a Purple Finch would do such a thing when a hawk is nearby convinces me that my claim is accurate. And it tells me that this so-called “song” is actually an “alarm call” that reveals the bird’s concerned state. So, the Purple Finch’s “vireo song” is not really a song. Rather, it’s an alarm call that might be confused with a vireo’s song and that is given in the presence of an aerial predator.
Got that? … a vireo-like song that is actually not a song and that is not made by a vireo, but rather by a finch!
Are any of you familiar with this vocalization of the Purple Finch? Do any of you take exception to my conclusion about its function? Has anyone ever heard them do this in the presence of an aerial predator? Am I crazy for thinking it is an aerial predator alarm response? Whatya think? Am I off the mark here, or have I really discovered something neat?