11 day old healthy duckling died

[Quacken]

Hi, we hatched a mallard duckling 11 days ago. She was very healthy, energetic and all seemed well. This morning she wasn't her usual self, was slower and sleepier and got worse as the day went on. My sister worried she was constipated and thought she had a hard lump at her anus so gave her a warm bath and gently massaged her tummy. She died in her arms not long after. Does anyone know why this might have happened? We successfully hatched 2 ducks last year and aren't sure what happened this time and are so upset.
The first photo was taken yesterday, the second 3 days ago.

 

[KaleIAm]

I'm very sorry for your loss. We could guess why this happened, but the way to know for sure is to send the body for a necropsy. I do this for my ducks who pass away and sometimes even my vets who were treating them are surprised with the findings.

You can do this by using an avian veterinarian or your state vet lab. We can help with the state lab if you are interested.