Yes, it is sour crop. The food that is in there has dissolved into a toxic slush. If the crop is still full, you would want to cleanse it and then treat her with probiotics and give her organic apple cider vinegar water for two weeks if she's showing no other symptoms. You also will want to determine the cause of the problem in the first place and fix that.
Glenda Heywood has a good article on cleansing a crop. PM me if you'd like it.
You will want to do this as soon as possible because the liquid in that crop will grow bacteria and yeast and make your bird sick(er).
The probiotics are to replace the bacteria that have been damaged by the toxic contents and pH of the crop dribbling into the rest of her digestive tract. They will also help fight against whatever bad bacteria and yeast make it to that part of the system. The organic apple cider vinegar (1 ounce ACV to one gallon of water) will help correct the digestive tract pH, provide more good bacteria, break down the feedstuff that are in the crop waiting to go through, and also provide more digestive enzymes to break down solid particles in the digestive tract. The pH of ACV at this solution is that of a healthy digestive tract which is unfriendly to good bacteria. the pH of the crop (and thus the digestive tract) now is unfortunately friendly to bad bacteria, so we must change that.
If you see runniness of droppings after four days of treatment after the cleaned crop, let the board know. Let us know in any case, please.
By the way - no more solid foods until she's over this for two weeks. No grains, no grit, nothing but crumbles, probiotics (plain yogurt, acidophilis tablets, etc), maybe the bread if it's soaked in something useful - BUT - it's too friendly for yeast infections, sooooo maybe not. Boiled egg yolks are a good healthy treat and will help her gut. You can also mix the yogurt in a small amount of unsweetened applesauce. The pectin is small, helps clean out the digestive tract of sludge from this, the pH is like ACV (can be used with it), and chickens like the taste so it's a good way to hide probiotics.
Incidentally - the organic apple cider vinegar (versus regular) isn't for the philosophy or organics, or snobbiness... it's because of the manner of production of it and what it still contains. It's still produced by fermentation. The bacteria that fermented it are beneficial to birds; it's called the "mother" of the vinegar and appears as some 'stuff' at the bottom of the bottle. Regular ACV is chemically fermented and doesn't contain the mother. Nor does it contain half the nutrients, enzymes, etc produced by the mother while it's on the shelf. So go organic.
