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Thursday, October 22, 2015

A shared interest

I had a funny experience a few days ago.  I walked outside of the house and heard a very loud, "Crrraack!"  I looked around, and noticed a large nut in the street.  And then I looked around some more, and noticed an American Crow flying down to the nut.

It made me smile for a few reasons.  I'm fascinated by corvid behavior, and this was the first time I'd seen a crow doing this using height, gravity, and a hard surface to open a nut.

It also helped me solve a mystery.  A few days before this, we had found a large walnut in the front yard (on a patch of cement).  There aren't any walnut trees growing adjacent to our house, so we wondered where the nut had come from.  When I saw the crow dropping the walnut on the street, I realized what had probably happened. 

And, seeing a crow with a walnut (and then finding many walnut shells in the area) also provided some circumstantial evidence for another puzzle.  You might recall that I've been watching some White-tailed Kites come to an evening roost, and that in the 1960s a large kite roost was reported in Cotati (see post from 5 October 2015).  Those kites were roosting in a walnut orchard, so I had been wondering about whether there used to be a walnut orchard near this house. 

Of course, I'm left with another piece of the puzzle exactly where are the crows getting the walnuts, and how far is that site from our house?  We'll have to start scanning for walnut trees in the neighborhood.

Perhaps both the crows and the kites have an interest in walnuts, but for different reasons?


Alice Chan said...

The first time I saw this behavior I was tickled pink. As I sat in my office in Bel Marin Keys, I noticed a crow fly down from the streetlight and pick something up off the street, then fly back up to the streetlight. As I watched,it did this over and over. Then it moved one perch down the street and kept doing it. So I went out to see what it was on the street that the crow was so interested in - and yes, it was a walnut. It was really interesting to watch. Since then I've seen it quite a few times. These critters' ingenuity never ceases to amaze me.

Jackie Sones said...

Hi, Alice! I didn't mention it, but the largest concentration of walnuts near our house was also under a streetlight. At first I wondered if the crows were trying to drop the walnuts on the street so they would be run over by cars, but because the greatest concentration of walnuts was directly under a streetlight and on a sidewalk (not the road), it seemed like it was the hard surface that was most important (and not the cars). It turns out this question (cars vs. hard surface) was studied years ago in Davis, and the researchers ended up with the same conclusion.

Margaret Pearson Pinkham said...

Crows do this on our street in Sebastopol. The walnut tree is at the end of our court, about a block away from the streetlamp they use. There are closer street lamps, I wonder why they use this one?

Jackie Sones said...

Hi, Margaret! Interesting observation and question. It's fun to think about why they're choosing particular streetlights. Do they learn from other crows? Have they had more success at breaking the walnuts there? Are there other birds or animals that compete with then for the walnuts closer to the tree?