While banding birds at Bob Thobaben’s farm west of Wilmington, OH, we caught a series of Field Sparrows with curious growths on their feet.  The first one we caught, we merely noted the presence of the growth.  An hour later, we caught another Field Sparrow with a similar growth.  Sensitized to the problem, we took some pictures of this bird.  Fortunately, it was a retrap.  Bob’s records showed that the bird had been banded only three weeks before.  No unusual growths were noted at that time.

Growth on second bird.  Right leg, ventral side

Left:  Growth on  right foot of second Field Sparrow, ventral side.   Right:  Same growth as seen from left side.

On the next round of the nets, we found still a third Field Sparrow.  This one had four growths of the same sort, two on each foot.

Left:  Third bird showing two growths on each on foot.  Right:  The whole bird.  The growths are barely discernible  at this scale

The growths are about a half a centimeter in diameter and look rather like oak galls.  Bob says he has not see anything like this in thirty years of banding.  Anybody out there know what this is?  How do we account for such a concentration in time, space, and species?  Also, these growths appear to be fast-growing.  What is the cause of that?

Science is all about questions.

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