I have a mated pair of Cayuga ducks that are about 8 months old and live outdoors in my 1/2 acre backyard. They have round the clock access to two ponds, a indoor shelter with straw, a heated floor, food, and water, and are also fed cracked corn, fresh peas, and oats on a daily basis. We recently also began giving our girl crushed oyster shells as she is regularly laying now.Sometimes they are fed other assorted greens and/or have live fish dumped into their pond. I noticed today that my female seems very clumsy. She was taking one or two steps, then either tripping and falling or sitting down in a roosting position. I inspected her feet and legs very carefully and did not see any signs of injury or distress. She is still eating and drinking, but but she seems almost unable to walk. I have her in her pen, which is covered in straw so she's not walking on any ice or snow in our backyard. Does anybody have ideas about what might be wrong or if I should be doing anything specific for her? Also, if I end up having to take her to a vet, does anybody know an aviary vet in the Colorado area? Thanks!