Their flight feathers are beginning to grow and prolonged hunger at this age could weaken them. For a gyrfalcon, strong flight feathers are vital. It's time for the mother to take things into her own hands and start hunting too.
She uses her immensely powerful wingbeat to gain height. Her incredible eyesight allows her to watch the ground below without being seen herself. Even at 1,500 feet, she can detect the slightest movement below. If the hares don't move, they are safe.
Once she identifies a target, she moves into the sun, so she can't be seen. That's only half the battle won. She now has to carry her kill miles back to the nest.