My mallard Gabby has this white fluid that drips from her vent, but this only happens when she is petted/scratched on the back. It smells pretty poopy and is sometimes thick and very white, but sometimes thinner and more transparent. Other than that this never happens. Is this a cause for concern? Sometimes it's a lot, sometimes not much at all comes out. She lays an egg a day every single day if that matters. Here is a video to show you, this amount is not much compared to some other times.