I am sorry to say that the bird was PTS on Friday. Since we are just starting out we thought it best to get a professional opinion and PM to better understand the situation; the verdict was clearly
impacted crop, which had almost cleared, but leaving the bird ultimately too weak to have survived a procedure.
Here's what we learned, which may be obvious to many but could be of benefit to others in the future:
1) Do not allow them access to fresh grass clippings. We put them in an area where our compst goes, thinking they would be sensible enough to sift through for the scraps of greens etc. Perhaps they were just too young having only had pellets until then did not know the difference.
2) Figure out whether the crop is sour or impacted. Looking back its obvious now, but the first symptoms where a full, fluidy crop and the impaction was still soft so hard to define.
3) Treat ASAP. We allowed ours a week where we dallied, trying to feed different things and hoping it would get better. Although fluids were getting through, and she was quite with it, all the time she got weaker. If it ever happened again, we would treat straight away, isolating her, off the food and regularly administering a little oil and massaging the impaction, lots. If that hadn't shifted it in a week, we might try the surgical procedure to empty the crop. Either way, its gotta be emptied.
So, it was sad for the little bird and quite a knock for us. But where we have made mistakes, better to reflect upon them, acknowledge what went wrong and share it for the benefit of others. We have a couple of new birds and a happy chicken run outside - long may it stay that way.