Last July, Karen alerted me that immature Red-tailed Hawks were frequently perching and calling in the woods behind her house. So I showed up one morning, waited for about an hour, and then delighted in the arrival of a youngster who landed and screamed loudly from high in a tree. Within seconds, an American Robin started calling excitedly from nearby, giving it’s sharp peek and softer tut-tut-tut alarm calls, probably because it had a nest nearby. Another songbird responded as well; one can hear a male Carolina Wren giving cheer calls (down-slurred rattling trills) in the background. Listen also for the harsh nasal mews of a distant Gray Squirrel, possibly also upset by the presence of the hawk (although his calls may have been coincidental):
American Robin and Carolina Wren sounding off in response to a perched and calling immature Red-tailed Hawk. 10:30 am, 24 July 2010 near Ludlowville, New York. Recorded by Lang Elliott.
I rather like this recording. I think it’s a fairly straightforward example of songbirds responding with alarm calls in the presence of a potential predator, an aerial predator in this case. But can we be absolutely certain the robin and wren are calling because of the hawk? Seems likely for sure, but maybe the Robin and Wren were upset because I was standing nearby. And maybe the distant Gray Squirrel didn’t give a whit about me or the hawk. I say this because I’ve heard Gray Squirrels give mewing calls on many occasions when there was no obvious or immediate cause; for this reason, I’m always hesitant to label them “alarm calls”.
One must always be extra careful when inferring causation from correlation, especially when basing one’s claims on just one or two observations. It is all too easy to misinterpret what is going on.