April 9, 2025: Egg Development (Week 1)

– Fertilization and Cleavage: After each egg is laid (usually every 48 hours), early cell division begins within the blastodisc if fertilization was successful.
– Embryo Formation: Around day 2, the embryonic disc starts differentiating into three germ layers (ectoderm, mesoderm, endoderm) which will form all tissues and organs.
– Heartbeat and Blood Vessels: By day 3 or 4, the tiny heart starts beating, and a web of blood vessels spreads across the yolk to deliver nutrients.
– Critical Window: Early development is especially sensitive to temperature fluctuations—consistent incubation is vital to prevent deformities or embryo loss.
– Yolk Sac Function: The yolk sac begins actively nourishing the embryo, which grows from a flat disc to a curled shape by the end of the week.

Adult Peregrine Behavior Patterns (Week 1 of Incubation)

Division of Labor
– Initiation of Full Incubation:
– Incubation begins in earnest after the third or fourth egg is laid to synchronize hatching.
– The female usually starts full-time incubation once the clutch is complete (often 4 eggs), and does the majority from the start.
– Male Support:
– The male may begin bringing prey more frequently and take short incubation turns (rarely more than 10–15 minutes early on).

Establishing the Rhythm
– The pair begins to settle into a consistent daily rhythm:
– The female incubates for hours at a time.
– The male perches nearby, hunts, and occasionally relieves her.
– Exchanges are brief and accompanied by gentle vocalizations, bowing, or mutual preening.

Territorial Vigilance
– Increased Defensiveness:
– The pair becomes more territorial and alert to potential threats.
– The male may perform territorial flights or warning stoops if other birds or humans come too close.

Nest and Egg Care
– Egg Turning Begins:
– Essential turning behavior (several times an hour) starts as soon as full-time incubation begins.
– Feathering and Shuffling:
– The adult may shift slightly to tuck the eggs into the brood patch (featherless skin area rich in blood vessels).
– The female often pulls in small stones or gravel with her beak to help cradle and insulate the eggs.