The growth and development of peregrine falcon chicks during the first two weeks after hatching are rapid and fascinating. Here’s a detailed overview:

First Week (Days 1-7)

Day 1-2:
– Hatching:The chicks, known as eyases, hatch after about 33-35 days of incubation. They emerge from their eggs with the help of an egg tooth, a small, temporary structure used to break the shell.
– Appearance: They are covered in white down feathers and have closed eyes. They are very small and weigh around 35 grams (about 1.2 ounces).
– Dependence: The eyases are highly dependent on their parents for warmth, protection, and food. The female, known as the falcon, broods them almost continuously to keep them warm, while the male, known as the tiercel, hunts and brings food.

Day 3-4:
– Feeding:The parents begin feeding the chicks small pieces of meat, often several times a day. The falcon tears food into tiny, manageable pieces to feed the eyases.
– Growth: The chicks start to gain weight rapidly, approximately doubling their birth weight by the end of the first week. Their digestive systems are efficient, and they produce a lot of waste, which is removed by the parents to keep the nest clean.

Day 5-7:
– Eyes Opening: By the end of the first week, the chicks’ eyes start to open. Their vision, initially limited, begins to improve, allowing them to start recognizing their surroundings and parents.
– Mobility: The eyases become more active and begin to move around the nest, though their movements are still quite clumsy.
– **Vocalization:** They start to make more vocalizations, calling out for food and interacting with their siblings and parents.

Second Week (Days 8-14)

Day 8-10:
– Feather Development: The down feathers begin to grow thicker, providing better insulation. The chicks still rely heavily on their parents for warmth, but can tolerate short periods without brooding.
– Appetite: Their appetite continues to increase, and the parents must hunt frequently to provide enough food. The tiercel often brings prey to the nest several times a day.
– Weight Gain: By the end of the second week, the chicks’ weight continues to increase rapidly, reaching around 150-250 grams (5-9 ounces), depending on food availability and individual variation.

Day 11-14:
– Further Development: The chicks’ eyes are fully open, and their vision sharpens. They become more coordinated and start to practice using their talons and beaks, essential skills for later life.
– Social Interaction: The eyases interact more with each other, sometimes engaging in playful tussles. These interactions are important for developing their social and physical skills.
– Independence: They begin to show brief signs of independence, such as preening themselves and exploring the nest area more actively. However, they are still completely reliant on their parents for food and protection.

Overall Growth and Development:
During the first two weeks, peregrine falcon chicks experience significant growth and development, laying the foundation for their rapid progression to fledging. Their physical development is complemented by increasing awareness of their environment and social interactions, setting the stage for the skills they will need as fledglings and eventually, as adult hunters. The parents’ role is crucial during this period, providing continuous care and an abundant supply of food to support the chicks’ rapid growth.