Deformed pansy/viola growth

Pattijessiman3

Hi.  I've got pansy's and viola's growing with 'deformed' flowers.  They look almost shredded.  No evidence of animal/fly damage elsewhere.  Leaves and stems quite healthy.  Plants are in different pots not all together.  Other pansys are flourishing which is odd.  
Deadheading is not stimulating new 'normal' growth.  Assume I'll need to get rid of plants but would like to know why its happening, can I rectify it and will it likely affect other plants.   

B3

Slug or snail damage when the flowers were buds

BobTheGardener

Or pecking by birds.  My local flock of sparrows have young in the nests and I think it is why they are pecking at all sorts of plants and flowers here.

herbaceous

I second the baby sparrows! They are such fun to watch but (like any toddler) quite destructive.......

Fairygirl

Yellow flowers are especially attractive to sparrows, so that's most likely.

Possibly some slug damage too. They annihilate pansies.

Asarum

I once had a beautiful male pheasant shredding some primula flowers in the same way!