How to know if a duckling is shrink wrapped without internal pip

[quackkquack__]

I was wondering how to know if a duckling is shrink wrapped without an internal pip. I've had to assist a shrink wrapped duckling without an internal pip before and she hatched fine but I don't remember how I knew she was shrink wrapped so I was wondering how to know so I can keep an eye out with my current eggs if they do get shrink wrapped (hopefully not)

 

[2ndTink]

@KathiQuacks