I'm not good at poopology but that does look different. Susanne has some info on abnormal droppings here:
http://tinypic.com/useralbum.php?ua=9f% ... FC5g%3D%3DMy suggestion would be to clean the aviary so you can tell the difference between new poop and old poop, then see if it happens again. Also keep an eye on the birds to see if anyone is acting abnormal. It can be hard to tell when you have a lot of birds, but especially try to see if everyone is eating.
If the odd poop doesn't happen again then it's no biggie. Bird poop isn't exactly identical every time and can vary depending on what they've been eating. It may not have been a real problem in the first place, and if it was a problem then it's fixed itself. If it does happen again you'll need to try to figure out which bird it's coming from and do something about it. There are some simple home remedies that can help with digestive upsets. Susanne has info on them here:
http://tinypic.com/useralbum.php?ua=MNW ... F7fw%3D%3D You might have some of these items at home already and it wouldn't hurt to give the whole flock a small amount in their food or water as a precaution. Susan prefers lemon juice over vinegar, but a little bit of vinegar would have pretty much the same effect as a little bit of lemon juice.