1. Size and Feather Growth: Initially, the falcons are small, fluffy, and covered with down feathers. However, as they grow, they progressively develop larger and stronger flight feathers, preparing them for their eventual departure from the nest.
- "Inside, five blind, white baby falcons were huddled together, their pinfeathers still sheathed in tiny white tubes." (Chapter 1)
- "Over the past couple of weeks, however, the nestlings' feather sheaths had plumped up and split, revealing brown flight feathers." (Chapter 1)
- "Now they were larger, their long pinions just emerging from their downy fluff, and they regarded him solemnly out of orange-brown eyes." (Chapter 3)
2. Wing Development: The young falcons' wings begin to grow and spread, which is crucial for their future ability to fly.
- "Their small wings twitched and flapped, growing stronger by the day." (Chapter 1)
- "Their brown wings were fully developed now, and they arched their wings and stretched them out, luxuriating in their newfound freedom and strength." (Chapter 5)
3. Head Changes: The falcons' heads undergo noticeable changes, including the development of a prominent knob on top of their heads. This knob, called the "cere," is associated with the growth of their bills.
- "Their cere was large and yellow like their mother's, but would eventually turn blue on the males and remain yellow on the females." (Chapter 2)
- "Over and over the birds would tilt their heads back and snap open their bills to catch food fragments or bits of dead skin that she dislodged." (Chapter 3)
4. Independence and Communication: As the falcons grow older, they become more independent and start communicating with each other and their parents through various vocalizations and gestures.
- "The eldest would rise, flapping her wings and chirping, and the others would follow." (Chapter 2)
- "The chicks stretched, flapping their wings and whistling softly to each other." (Chapter 3)
- "'Kree. Kreeee,' they called out, their voices loud and strong, echoing through the canyon." (Chapter 4)
5. Hunting Behavior: The falcons observe and learn from their parents' hunting behavior, and they start practicing short flights and capturing prey with their talons.
- "Every morning, Drum and the Duke would return with bloody offerings plucked from the canyon floors - grouse, ptarmigan, and ground squirrels." (Chapter 1)
- "The young birds watched their parents hunt, swooping down on unsuspecting victims with deadly accuracy." (Chapter 4)
- "He stretched out his foot and tried to capture another piece of meat, but his talons were still too weak to hold it securely and it fell to the ground." (Chapter 5)
These are just a few examples of the physical and behavioral changes that occur as the young peregrine falcons grow and develop under the watchful eyes of their parents.