Crease on ducks chest?

[Pekin duck mom]

My Pekins get this crease (I guess you would call it) on their chest, on and off all the time! What is that? Some have it sometimes and others other times. Should I be concerned? They eat plenty and are fine otherwise and it goes away. What is causing it and what can I do about it?

 

[JacinLarkwell]

Pictures?

 

[Pekin duck mom]

It seems to go away a while after they eat. maybe just an empty stomach? Its just that its every day and I feed them plenty! I probably overfeed actually...

 

[Isaac 0]

Some Pekins have a crease down the medial thoracic aspect, that is not uncommon.

 

[Pekin duck mom]

Some Pekins have a crease down the medial thoracic aspect, that is not uncommon.

Ok thank you!! I didn't figure it was but just wanted to be safe.