Egg binding: (noun) When the female bird (hen) is unable to lay its eggs because of a disruption of the process, which could be due to disease, lack of exercise or calcium, etc. It is especially common in budgies, lovebirds and cockatiels. Contact an avian veterinarian immediately if you suspect your bird is egg bound. Deter your bird from seeking out nesting sites or building a nest, and reduce the amount of sunlight and warm foods it gets during breeding season.
Watch Poppy, a cockatiel, lay her first egg and try to incubate them. (She is not egg bound.)