It is unusual to find a bird eating leaves.

I watched this female Rose-breasted Grosbeak (Pheucticus ludovicianus) feed on in this Boxelder (Acer negundo) for some time as I photographed her. What struck me most is that she was eating leaves. Not just any leaves, the red ones. These are leaves containing insects that form leaf galls. I don't know what particular insect was inside the gall, possibly an Eriophid mite, but she clearly was interested in consuming only those leaves with the red galls.

I guess when the bugs are small and encased in a leaf gall, it is just as easy to eat the plant with the gall to get the bug.

An insect-caused leaf gall forms when an adult insect lays eggs on a leaf and then the eggs hatch and the insect larvae begin feeding on the leaf.

Location: Magee Marsh State Park, OH