Ok so I have 3 - 2 week old Pekin Ducklings, a Drake and 2 hens. I ordered them though the local feed store and received them on Thursday, October 1. All 3 seemed to be in tip top shape. They all eat well and drink plenty. I give them a starter crumble that is 22% protein and is medicated... all natural medication, according to the feed store owner. At any rate, this issue started before they were switched over to the new food. I keep them in the house in a pen with a heat lamp as I have a mother hen occupying the nursery coop and yard with chicks at the moment and she is not fond of intruders... unless you come bearing raisins. I give them free reign in 15 minute intervals every few hours... they have full access to food and water at all times, and are allowed 10 minute supervised baths in my kitchen sink where they dive and splash and make a wonderful mess of my counter tops and floor. Three days ago now as we were getting baths taken and getting ready to settle down for the night,I noticed what looked like a thinning spot on her neck. As they splashed and made their glorious mess on my kitchen counters and floors I noticed that the bigger of my 2 hens was sitting a little lower than normal in the water. The area of her back directly behind her neck was submerged where as the other 2 were floating with their entire backs out of he water. I let her go for a couple more minutes and let her swim and splash, keeping a close eye on her. As she turned from the back of the sink and dove under the water toward the front and me, I noticed that that thinning area on her neck was rather inflated and took her out to have a closer look. Upon closer inspection, I discovered that the area was indeed larger and apparently inflated. It was not any warmer than the rest of her body, no lumps, no fluid that I could see, and very transparent. I was able to see inside her neck. She did not object to my touching it at all and it does not seem to hurt her at all. I have done tons upon tons of searching on the topic and have read about everything from ruptured air sacs to tumors. Unfortunately to no avail. She does not seem to be in any kind of distress and we do not have an avian vet in my area. I have no idea what it might be or what to do about it. If anyone has any info on the issue I would be eternally grateful. I am attaching pictures in the hopes that someone will have seen or dealt with something similar and can help... Again, Thank you in advance for any help or advise you can offer on the matter.