When a budgie lifts one wing, it is typically a sign that something is wrong. Budgies are very active birds, and they use their wings to fly, climb, and balance. If a budgie is lifting one wing, it may be experiencing pain, discomfort, or illness.
There are a number of potential causes for a budgie to lift one wing. These include injuries, infections, and nutritional deficiencies. In some cases, a budgie may also lift one wing if it is feeling stressed or anxious.