Most bird species have a suite of vocalizations that they draw on to use in different situations. Snow Buntings have a marvelous song that, for me, conjures up sweeping Arctic vistas. But they also have an electric alarm call. Snow Buntings nested in rocky nooks and crannies in the huge scree field at the base of the cliffs at Cape Vera on Devon Island. Arctic Foxes would regularly stroll through the rocks looking for bunting nests (or lemmings). You could follow the fox’s progress by listening to the alarm calls as it moved – the bunting in one territory would give the call and follow the fox until it moved into the next territory at which point that bird would pick up the alarm. And so on across the extensive area. It was a loud, sharp call that carried a long distance.
Donald Kroodsma in his book Birdsong of the Seasons, notes that an alarm call “alerts individuals of the same species and other species” of a potential predator. I wondered about this: does a particular species recognize the alarm call of another species and understand its meaning – danger!
We had a chance to check this out yesterday while bunting banding. We were catching buntings consistently (68 banded) but not in large numbers at any one time – small flocks of 10-12 birds would fly in, feed, and then fly off. When the traps collected around 10 birds we’d empty them, band the birds and then let them go – out the window of my car. Almost always when the banded bunting was released it would speed away giving its alarm call.
Usually, when we cleared the traps and returned to the car, birds would be back at them before the door was closed. Initially we were catching only Snow Buntings but a little later in the morning four Horned Larks showed up to check things out. This is a pretty common combination: larks and buntings. We noticed that when a bunting was released after banding and gave its alarm call the birds that were around the traps would fly up and away – both buntings and larks. They would fly about 15-20 meters, land on the snow and then return to the bait area….until another bunting was released. At the alarm, both species took off – it appeared that the larks were responding to the bunting’s alarm call. But…were they?
At one point we had half a dozen buntings in the car for banding and there were only the 4 larks around the traps – the buntings had not returned. Here was our chance to find out. In this scenario, each time a bunting was released and called the larks did not respond at all. This happened with all 6 buntings – no response from the larks; they just kept walking around the traps looking to snap up any corn that had made it outside the mesh.
Often, when we’re releasing freshly banded Horned Larks they will give their alarm call. The larks in the vicinity will usually do one of two things: flatten themselves to the snow surface and scan the sky or take off. But they weren’t doing this in response to the bunting call. I think the important thing here is that the bunting alarm call causes other buntings to take wing. Larks, mixed in with them, respond to their flight and take wing as well. But they are not responding to the call, just to the startled bunting movement.
Of course this was a pretty small sample size (4 birds) and only one test. But it will be interesting to try and follow up on it. Hey! Maybe I can get a grant…..