Newsworthy nuthatches

20 03 2007

A walk through the woodlands after a fresh snow can bring a needed meditative silence at the end of a busy day. But sometimes silence is short-lived, and if you’ve ever found yourself suddenly surrounded by a flock of scolding chickadees, then you know what I mean! The flipside is that, if you’re ever looking for something interesting in a woodland that seems devoid of birds, listen carefully and you might be rewarded with the buzzy alarm calls used by many of the resident winter birds that live in groups.

BCCH spectrogram

(A spectrogram of the “fee-bee” of a chickadee followed by two buzzy “chick-a-dee” calls, each with 4+ “dee” notes, suggesting a mobbing call)

These alarm calls are like an auditory advertising billboard; with a dominant mid-range frequency, they are repetitive and loud, and it is easy to home in on their source. And often, what you find at that source is something, well, alarming (at least to a chickadee), like a small owl or an accipiter (e.g., the Cooper’s Hawk below).

coopy

It turns out that birders aren’t the only ones using these advertisements to find potential predators. In fact, up to 50 different species have been noted to respond to chickadee alarm calls, and they typically join the group of scolding chickadees in a behavior called “mobbing“. The ultimate function of mobbing is unknown, but past studies have suggested that it may be a social tool to identify predators and/or an advertisement to a predator of the mobbing bird’s knowledge of the predator’s presence. Mobbed predators have been shown to depart more quickly (there’s a neat movie here) than un-mobbed predators, which suggests that resident birds can affect a predator’s foraging habits simply by ruining it’s chances of a surprise attack (and an easy meal). Other animals are known to perform advertisements of their knowledge of a predator’s presence, most notably the “stotting” performances of Thomson’s Gazelles that inform a lurking cheetah that it has been spotted, and a difficult, energy-intensive hunt will result if it proceeds.

rbnut

Enter the newsworthy nuthatches…

A researcher at the University of Washington recently published a paper detailing the behavior of red-breasted nuthatches exposed to chickadee mobbing calls. Nuthatches are common members of winter flocks of forest birds, and you might expect that they would respond to the alarming calls of chickadees (which they do). The interesting part of the story is that nuthatches respond more strongly to alarm calls made while chickadees are mobbing a pygmy owl (an important predator of small birds in the West) than alarm calls broadcast while chickadees mobbed a great horned owl (a virtual non-predator). The structure of chickadee mobbing calls change with the threat level presented by a predator, with the number of “dees” and the calling rate increasing as the potential threat increases.

So next time you find yourself listening to the eponymous calls of the chickadee, listen carefully like a good nuthatch and you might find that you already know what all the fuss is about: “dee” is for danger!

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5 responses

20 03 2007
mon@rch

Very cool post! Love the spectrogram that you included! Bird sounds and vocalizations are soo interesting!

21 03 2007
Nuthatch Scrutinizes Chickadee Calls « surf.bird.scribble.

[…] if the newspaper reports left you wanting to hear more, check out the Nuthatch’s own take on the research, complete with discussion of the fine points, links to background articles, and a sound spectrogram […]

24 03 2007
Barbara

Loved this post. I love learning about birds. Thank you.

26 03 2007
George Dillmann

How about that on the number of “dee” notes – I’ve noticed that under most conditions, I hear 2 or 3 “dees” from the chickadees near my feeder. Yet when I go out to take the feeder away to refill it, I often hear 4 “dees” come from the nearby trees!

1 02 2008
Mobbing of a relaxed sort « the contemplative nuthatch

[…] this day, a blue jay that had actively been mobbing the RSHA took a break from antagonism and joined the hawk around the figurative […]

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