Peregrine Falcon chicks: Week 4

June 16, 2024 in Peregrine Falcon Woburn

During the fourth week after hatching, peregrine falcon chicks (eyases) continue to undergo significant changes in preparation for fledging.

Day 22-24:

– Feather Development: By now, the chicks have a substantial amount of juvenile feathers, especially on their wings and back. The down feathers are mostly replaced by these juvenile feathers, which are darker and more streamlined.
– Weight and Size: The chicks continue to grow, with their weight reaching between 500-800 grams (18-28 ounces). Females are typically larger than males.
– Preening: Preening becomes more frequent as they take care of their feathers. This behavior helps ensure their feathers are in good condition for future flight.

Day 25-27:

– Wing Exercises: The chicks engage in vigorous wing flapping to strengthen their muscles. They may even start to lift slightly off the ground, practicing for their first flight.
– Mobility: Their movements become more coordinated and confident. They explore the nest area more thoroughly, hopping and walking around.
– Feeding: The parents continue to bring food, but the chicks may start to eat more independently. They can tear apart small pieces of meat on their own, though they still rely on their parents for larger prey.

Day 28:

– Social Interactions: Interactions with siblings become more complex and frequent. They engage in playful mock battles and other social behaviors that help them develop their hunting and survival skills.
– Vocalizations: The chicks’ vocalizations become more varied and sophisticated. They communicate more effectively with their parents and siblings.
– Independence: While still dependent on their parents for food, the chicks show increasing signs of independence. They may start to watch the sky more intently, observing their parents’ hunting and flying techniques.

Overall Development During the Fourth Week:

The fourth week is a crucial period for peregrine falcon chicks as they prepare for fledging. The significant growth in their feathers and the development of their muscles and coordination are essential for their first flight. The chicks’ increasing independence and social interactions also play a vital role in their preparation for life outside the nest. The parents continue to provide food and protection, but the chicks’ growing autonomy signals their readiness to leave the nest soon.

Peregrine Falcon chicks: Week 3

June 9, 2024 in Peregrine Falcon Woburn

During the third week after hatching, peregrine falcon chicks (eyases) continue to experience significant physical and behavioral development.

Day 15-17:

Feather Development: The down feathers are gradually replaced by darker juvenile feathers, especially on the wings and back. These juvenile feathers are more streamlined and will eventually aid in flight.

Increased Size: The chicks continue to grow rapidly, with their weight now ranging between 250-400 grams (9-14 ounces). Their bodies become more robust, and their legs and feet grow stronger.

Hunger: Their appetite remains voracious, requiring the parents to provide a steady supply of food. The tiercel (male) continues to hunt frequently, bringing back prey which the falcon (female) helps to feed to the eyases.

Day 18-20:

Mobility and Coordination: The chicks’ movements become more coordinated. They start to stand on their feet more reliably and may take short, wobbly steps around the nest. This increased mobility helps them exercise their growing muscles.

Preening and Wing Flapping: They begin to preen more frequently, taking care of their developing feathers. Wing flapping becomes more common as they start to build the strength necessary for flight. These flapping exercises are crucial for developing their pectoral muscles.

Social Behavior: Interactions between siblings become more complex. They may engage in mock battles, which help them develop hunting and defensive skills. These playful activities are essential for learning social hierarchies and improving coordination.

Day 21:

Further Feather Development: By the end of the third week, the chicks have a noticeable amount of juvenile feathers. They still retain some of their down, but the sleek, darker feathers are becoming more prominent.

Weight and Size:Their weight continues to increase, with females generally larger than males. By now, the chicks weigh between 350-550 grams (12-19 ounces).

Vocalizations: Vocal communication becomes more sophisticated. The chicks use a variety of calls to communicate with their parents and each other, often demanding food with loud, persistent cries.

Independence: While still heavily reliant on their parents, the eyases begin to show more signs of independence. They explore their immediate environment more confidently, occasionally venturing to the edge of the nest.

Overall Development During the Third Week:

The third week is a period of intense growth and physical development for peregrine falcon chicks. Their transformation from fluffy, down-covered eyases to more sleek, feathered juveniles is well underway. The increased mobility, coordination, and strength they develop during this period are critical for their upcoming stages of development, particularly as they prepare for fledging. The parents continue to play a vital role in providing food and protection, but the chicks’ increasing independence and curiosity signal their gradual transition toward self-sufficiency.

Peregrine Falcon chicks: Week 2

June 2, 2024 in Peregrine Falcon Woburn

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.

Peregrine Falcons: copulating in Woburn!

March 18, 2018 in Peregrine Falcon Woburn, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

_W7I3264-001Made a short stop to observe the Peregrine Falcons in Woburn this morning.  Upon arrival, stopped initially at quite a distance to focus binoculars on the female.  She was perched on an upper ledge well to the west of the nest ledge.  Moments later, from out of sight, the male launched into a big swooping dive and then moved up towards the female.  He approached her from the air and landed on her back with clenching his talons in a ball and resting on his tarsi.

Typically, as the male prepares to mount, the female sleeks feathers, crouches, and leans forward, and may move her tail up and to side. During copulation, the female is normally at an angle of about 45° with wings slightly lifted and extended (from elbow), sometimes tail partly spread. The male makes every effort to maintain an upright position throughout copulation by flapping wings high above body and balancing on his tarsi with closed toes and feet turned inward. During copulation, the male’s neck is extended and curved; he chitters while she gives copulatory wail.

After close to ten seconds, the male departed and landed in the nest ledge and the female remained in place.

Reference cited:

White, Clayton M., Nancy J. Clum, Tom J. Cade and W. Grainger Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.


Peregrine Falcon: Woburn

March 12, 2018 in Peregrine Falcon Woburn, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

_W7I2207-001A short visit to the quarry in Woburn under clear skies, bright sun, light wind, and temp around 24F.  While scanning all around with no peregrines in sight, a streaking bird came in from the west, one of the peregrines, and swooped up in long arc, to the nest ledge.  It spent a bit of time preening.

One thing the peregrine falcon does a lot is preening. A number of hours are spent each day, particularly on the care of feathers.  The preening is in fact a necessity to keep feathers net and clean!

Peregrines chasing Ravens: Woburn

February 7, 2018 in Peregrine Falcon Woburn, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

_W7I6848-001The peregrines reacted to calls and activity of nearby Raven pair; the female made a number of flight loops out and around area of Ravens and back to a ledge perch each time. No direct approach towards the Ravens, but a gentle and firm message of territorial warning!

According to Tom Cade’s proposed model, with nesting cliff as center: there are a series of threshold perimeters surround eyrie with decreasing defense as distance from eyrie increases. Inner perimeter may be only 200 m; within that, attacks always occur. In outer perimeter, attacks only occur over food or favored perches.

_W7I6947-001The peregrines may be seen making flight patrols of area around nesting cliff.  This may take place when adults fly along cliff face or top to a given distance, turn, and repeat course, frequently in seemingly relaxed, but intentional flight. Often intruders, including Ravens, Red-tailed Hawks, and others are stooped at, sometimes jointly by pair, and loud, assertive cack calls are given.  The message of territorial boundaries is being conveyed loud and clear!

Literature cited:

White, Clayton M., Nancy J. Clum, Tom J. Cade and W. Grainger Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Female Peregrine feeding: Woburn

January 29, 2018 in Peregrine Falcon Woburn, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

_W7I6174-001Made a morning to visit to Woburn Peregrines and found the female ripping apart freshly caught prey atop utility pole just to the right of the Herley NE building.

Here is a recap on  peregrines and typical eating after the capture process from Birds of North America Online:

After biting into neck, falcon carries will typically carry prey to habitual plucking perch (tree snag, cliff side, utility pole, building) for consumption, or to cache site. Prey too heavy to carry in flight are partially consumed on ground; remains may later be carried to eyrie or plucking perch, or left in place for later return. 

_W7I6104-001The peregrine begins eating by tearing off head; usually consumed if small, picked apart and eaten or discarded if large. Continues by pulling apart and eating skin and flesh of neck (also bones of small prey), working down to breast. Depluming of breast precedes tearing into pectoral muscles, which are usually totally consumed. Viscera may or may not be eaten; often gut is pulled out and discarded, but remaining organs, especially heart and liver, usually eaten. Legs of large prey may or may not be picked clean.

Appears to use tomial teeth to break long bones of wings and legs of smaller prey before swallowing. Large prey too heavy to carry back to eyrie are well plucked wing and tail feathers removed, head removed, eviscerated, and sometimes posterior half of carcass detached from breast, before latter carried back to eyrie to feed young.

Literature cited:

White, Clayton M., Nancy J. Clum, Tom J. Cade and W. Grainger Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Peregrine Falcon: Woburn – bulging crop

December 6, 2017 in Peregrine Falcon Woburn, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

_W7I1470-001Made a short visit to search for the peregrines in Woburn under mostly cloudy skies, wind blowing from the west at 16MPH with gusts over 20MPH.  Observed the adult female falcon on a perch to the left of the nest ledge.  Great looks at the female with a very full crop. The crop is the name of the part of the falcon’s anatomy that serves as a storage area for food until it is passed to the stomach – often seen as a bulge in the upper part of the bird’s chest area when it is full.

Peregrine Falcons: Woburn pair

November 15, 2017 in Peregrine Falcon Woburn

_W7I7170-001A beautiful morning with clear skies, bright sun and light winds!  Both adult peregrines continue to be seen most days around the quarry area.  This morning the male was perched at the front edge of the nest ledge with the female nearby.  She departed in pursuit of a passing hawk and then promptly returned, likely after engaging in a little territorial defense.  She returned to a regular perch atop Pinnacle Rock.

Peregrine Falcons: Woburn pair on pole

November 12, 2017 in Peregrine Falcon Woburn

_W7I6964-001Made a visit to the Peregrine Falcons in Woburn on sunny Sunday afternoon.  Discovered both adults perched on the double cross bar utility pole located on the south side of the main parking lot.  It was a beautiful afternoon with bright light, little wind and temps in middle 40’s.  Had a nice opportunity to pause for closer looks at the female as she was resting with a full crop after a recent meal.

_W7I6964-002Took a moment to observe and appreciate the nostril cone; falcons have a cone (baffle) just inside each nostril that disrupts the air flow and reduces the pressure of the air entering the respiratory system…also a nice look at the tomial tooth, known as the “killing tooth.” It is a notch on the cutting edge of the upper beak that is used to sever the prey’s spinal column.