Downy Gets Gall

by Carl Strang

Last week I had the opportunity to see something I had heard about, had seen signs of, but never had observed myself. I saw a downy woodpecker going after goldenrod gall fly larvae. The bird was a male, like this one.

He was in an open area between the north and south savannas at Mayslake Forest Preserve. He was gripping a tall goldenrod stem with his feet and precisely, quickly hammering a small hole to reach the center of a goldenrod ball gall. He needed only a couple minutes to finish before moving on to the next gall. I photographed the one he opened.

The gall fly larva (Eurosta solidaginis) was gone. Several nearby galls had similar holes. A few questions come to mind. Is this usually the time of year when these birds go after this prey? How does a given woodpecker get started (once he has gotten the idea and has begun, he can go from gall to gall, but how does he learn that there is food here to begin with)?


  1. jomegat said,

    November 16, 2010 at 7:27 pm

    It wouldn’t surprise me to learn that they can hear the gall flies.

    • natureinquiries said,

      November 17, 2010 at 6:48 am

      Thanks, that’s a good suggestion. Another possibility I would like to watch for if I get the chance is to see whether the woodpeckers give the galls exploratory taps. That might give them information about the inside, or stimulate the larva to move and make a sound as you suggest.

  2. March 4, 2011 at 6:58 am

    […] fall I posted an observation of a downy woodpecker opening goldenrod ball galls to get the larvae of gall flies. I did not stop […]

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