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Wednesday, October 17, 2012

Warm or cold?

We've had some very warm nights and some very cool nights in October.  In the beginning of the month, there were nights that stayed at 70-80°F.  During the second week of the month, evenings cooled down to ~50-60°F.  These contrasting temperatures offer wonderful opportunities for comparing the calls of crickets.  The temperature affects the chirp rate and the pitch of their calls.

Here are two recordings of the same species, one made on a warm night and another on a chilly night.  Can you tell which is which?

(If you are reading this in an e-mail message, click on the title of the post above to access the sound clips on the web site.)


cricket 1 by nhbh


cricket 2 by nhbh


The first recording is from a cold night (slower chirp rate, lower pitch) and the second is from a warm night (faster chirp rate, higher pitch).

If you've been hearing similar sounds and haven't yet seen the animal responsible, here are a few photos.

This is a tree cricket.  I photographed and recorded these individuals in our garden in Sebastopol.  The first image shows the tree cricket resting on a leaf with its wings down over its abdomen.



To produce their calls, tree crickets raise their wings up (almost vertically) and rub the edge of one wing against a file-like structure on the other wing.  The next two photos show males in an active singing position.



To see a video of a singing male with wings in motion, check out this web site about tree crickets.

It's fairly easy to find tree crickets when they're calling.  Bring a flashlight or headlamp and focus your ears on the origin of the call.  Keep the flashlight pointed down until you think you know where the call is coming from.  Move slowly and quietly towards the sound, as the cricket may stop calling if it senses a possible predator nearby.  When you're close, shine the flashlight directly at the spot where you think the cricket is.  Sometimes it takes several attempts, but you'll be successful if you keep trying!
 

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