What plants? The only time I have seen something like that was with sunflowers and the gold finches were anxious to get at the seeds so they pulled at the petals.
If your flowers are something the birds like, I understand, but if you are talking stuff like marigolds and calendula and snaps, I don't think it's birds.
Linda C

Goldfinches will cling to the petals with their toes while they eat seeds. So, it looks like the petals have been plucked out, but it's the grip with the feet that seems to do the most damage. I plant for birds, so I don't worry about it.

Cameron

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