Monthly Archives: April 2025

Lawrence Peregrines: Incubation Week 3

April 23, 2025 in In the Nest Box

Wed. April 23: During the third week of incubation for a pair of nesting Peregrine Falcons (around days 14–21 after the last egg is laid), several key things happen in the development of the eggs and in the daily behavior of the adult falcons. Here’s a summary focused on your pair north of Boston:

Egg Development (Week 3)
– Embryo Growth: By the third week, the embryos are well developed, with feathers beginning to form, and their movements inside the egg become more noticeable. They are actively turning and shifting position, preparing for hatching.
– Vascularization: The blood vessels are fully extended in the egg membrane, aiding efficient gas exchange—essential as the chick grows.
– Yolk Absorption Begins: The yolk sac, which nourishes the chick, starts to be absorbed internally, especially near the end of this week.
– Hatching Preparation: By day 21, the embryos begin positioning themselves for pipping (breaking through the shell), which typically occurs between days 33–35 of incubation.

Adult Peregrine Behavior Patterns (Week 3 of Incubation)

Division of Labor
– Incubation Shifts:
– The female (typically larger) continues to do the majority of incubating, especially at night and during colder, windier times.
– The male relieves her for brief periods during the day—often mid-morning and mid-afternoon—allowing her time to feed, preen, and stretch.
– Exchange Ritual: They often vocalize softly to each other during nest exchanges, with the male bringing food and the female calling or even bowing slightly before rising off the eggs.

Foraging and Food Delivery
– The male is the primary hunter during this period.
– He catches small to medium birds (e.g., starlings, pigeons, shorebirds) and delivers them to the female.
– Sometimes food is cached nearby, but during incubation, fresh delivery is preferred.

Nest Defense and Territory Vigilance
– Both adults remain highly vigilant.
– The male frequently perches on nearby vantage points to scan for intruders (other raptors or people too close).
– They may engage in aerial displays or alarm calls if disturbed.

Rest and Maintenance
– The female rests frequently while incubating, shifting slightly every 20–30 minutes to rotate the eggs and maintain even warmth.
– The male*may also be seen preening, calling softly, or engaging in short flights.

 

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Lawrence Peregrines: Incubation Week 2

April 16, 2025 in Near the Clock Tower

April 16, 2025: Egg Development (Week 2)

– Rapid Embryonic Growth: The embryos begin developing visibly defined features such as limb buds, eyes, and a beating heart. By the end of this week, they start to resemble tiny birds.
– Increased Metabolic Activity: Nutrient absorption from the yolk intensifies, and the demand for oxygen grows as organs continue to form.
– Membrane Development: The inner shell membrane thickens, and the chorioallantoic membrane—critical for respiration and waste removal—expands across the inner shell.
– Egg Turning: Regular turning of the eggs by the adults helps prevent the embryo from sticking to the shell membrane and ensures even warmth and proper development.

Adult Peregrine Behavior Patterns (Week 2 of Incubation)

Division of Labor
– Incubation Roles:
– The female remains the primary incubator, staying on the nest the majority of the time.
– The male does brief incubating stints, often 5–20 minutes, while the female feeds or preens.

– Shifts and Communication:
– Nest exchanges are polite and purposeful, often involving soft chirps or trills between mates.
– The female may stretch or circle briefly before resettling on the eggs after a break.

Foraging and Food Delivery
– The male continues to supply most of the food:
– He may hunt multiple times a day depending on weather and prey availability (typical prey includes pigeons, starlings, flickers, and shorebirds).
– Food is sometimes partially plucked before being brought to the nest ledge or a nearby feeding perch.

Territory Defense
– Both adults maintain a strong presence near the nest site:
– The **male** often perches nearby to guard the nest and watch for threats.
– They may engage in noisy aerial displays or stoops if another raptor approaches.

Incubation Behavior
– Egg Turning: Both adults turn the eggs several times per hour using their beaks and talons—an instinctive behavior to promote healthy development.
– Temperature Regulation: The adult on the nest adjusts its posture in response to wind, rain, or direct sun, creating an ideal microclimate for the eggs.

 

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Lawrence Peregrines: Incubation Week 1

April 9, 2025 in In the Nest Box

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.

 

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