Lawrence Peregrines: week of March 20, 2023

March 26, 2023 in In the Nest Box, Near the Clock Tower

March 20, 2023 under clear skies, wind W at 13MPH, temp at 36F. After searching all around the Clock Tower, made way for the red brick Pacific Mills smokestack and located one of the Peregrines sunning and preening on the east side of the stack near the top. This was a common perch location last year when the nest ledge was under the Casey Bridge. Image just before 10AM.

Just a few minutes later while looking for the second falcon, made a possible sighting and then confirmed right away. The other falcon was perched up near the top of the Clock Tower, on the top of a north facing window frame in the shade, and just keeping an open eye. Image at 10:06AM. The falcons have not been in or near the nest box over the past week, so stay tuned!

March 21, 2023 at 10AM under overcast skies, wind SW at 5MPH, temp at 44F. After initial scouting around the Clock Tower, headed west on Merrimack Street and turned north onto the Casey Bridge. About halfway across the bridge, noticed the male Peregrine perched on one of the Pacific Mills rooftop edges facing south with a gaggle of Crows nearby. The male appears to have a full crop. Peregrines like many other birds, come equipped with an anatomical feature known as a “crop.”  It is essentially a widened pouch at the bottom of a Peregrine’s esophagus, just above the stomach.  Peregrines can store food in their crops and then, slowly transfer it to their stomachs as they digest. They will often display a noticeable swelling in their chests when their crops are full.  The male has a very full crop, strong evidence that it had just finished a meal!

Minutes later, discovered the unbanded female lounging on the SW rooftop corner of the Mill240 building. This has been a regular perch location this spring, and provides an excellent vantage point both up and down the Merrimack River. The river is a significant flyway for all kinds of local birds and ducks. She heard the active call from the male and launched into flight and landed on the red brick Pacific Mills smokestack.

March 22, 2023, just after 10AM, under clear skies, wind NE at 6MPH, and temp at 46F. Great news this morning while checking the New Balance web cam! Not one but both male and female Peregrines inside the nest box. The male had been finishing off a meal with the female out on the perch. The female came in and then the male was seen pushing gravel around in the bowl-shaped “scrape” area in the back left corner from the camera view. One or another of the pair can often be seen to lean forward, pushing with its talons, to use its breast to form the substrate into a bowl (scrape) where the eggs will be laid.  Scraping is part of courtship. The birds continue to work on the scrape in preparation for egg laying. Eggs should appear sometime toward the end of this month, or first week in April at the latest. Stay tuned!

March 23, 2023 under overcast skies, wind W 12MPH, and temp at 59F. Made a late afternoon visit to the Clock Tower and found both Peregrines on upper ledges.

Female in flight……

Male cleaning his bill on roof edge after food exchange

March 24, 2023 under mostly cloudy skies, wind W 8MPH, and temp at 44F. Webcam in the morning, male working on the scrape by laying his chest down and and using his legs to forward to deepen the scrape bowl.

March 26, 2023 at just after 6PM, under clear skies, strong W winds at 16MPH with gusts to 26MPH, and temp at 54F. The female continues to linger and spend time in the New Balance nest box.

Lawrence Peregrine: hatchlings first days!

May 4, 2020 in In the Nest Box, Peregrine Falcons Massachusetts

2020.0504.1-001What an amazing weekend! Temps neared 80 for many communities yesterday afternoon, with that 78 in Boston, being the warmest day since October 7th of last year. Today, temps step back by about 10 degrees, hovering around 70 early this afternoon. We’ll also have more towering cumulus clouds that build up, producing a few scattered, brief moving showers mid to late afternoon. While most of the day is dry, occasionally the 4 new Peregrine hatchlings may have a passing shower or two in the afternoon! This first photo shows the female returning to the nest with fresh food for the chicks!

2020.0504.2-001The female was seen brooding and feeding the chicks this morning around 7:30AM.  She broods all four chicks.  She departs for a few moments and returns with food and she prepares to feed the chicks, while taking a few bites for herself. The female assumes an increasingly elevated brooding position as the chicks grow, and is especially careful with her feet when rising and moving away.  The brooding female gently pulls back with the underside of its beak, as needed, one of the small chicks, which moves out from under her, as she might hook a displaced egg. Female attentiveness to brooding depends on weather, the number of nestlings, and their age.  Brooding tends to become increasingly sporadic after about the eight day.


Literature cited:

Ratcliffe, D. 1993. The Peregrine Falcon. 2nd ed. Carlton, England: T. and A. D. Poyser.

Lawrence Peregrines: hatchlings!!

May 1, 2020 in In the Nest Box

2020.0501.2-001Finally the fourth egg has hatched and the hatchlings are all gathered in close together and being warmly brooded by the female! In most years, the eggs tend to hatch close to one another in a fairly well synchronized way, and within 24 – 48 hours of each other.  We have seen the remaining egg shells around the hatchlings.  The adults may move these around a bit with their bills.  They may seem to nibble a bit on the broken pieces, but they don’t have a well developed habit for disposal of the egg shells.  For the most part, the remaining pieces of egg shell will become trampled. Here the male departs as the female gets down to feeding the hatchlings!


2020.0501.3-001The hatchlings have a delicate white down at birth, with none of the coloration that will come later with true feathers.  They form a feathery white cluster in the first few days and remain in very close contact with one another as though in a rugby scrum! It is always a joy to watch the female feeding in her new little family. she does so with care and tenderness, making sure all receive a fair portion.

Lawrence Peregrines: incubation process

April 4, 2020 in In the Nest Box

Let’s take a look at the overall incubation process and what happens in the early stages! 2020.0402.LPBoth sexes have paired lateral brood patches. Less well developed in male. Belly area may function as patch also but less edematous and vascular than breast (TJC).  In this photo, the male is taking a break on outside edge of the nest box.  He waited a while until the female showed up and set down on the perch pole outside the nest box.

Incubation Period

The peregrines at this location have usually incubated their eggs for 29 to 33 days. In the early days of brooding it’s important to keep the eggs as close to their ideal incubating temperature as possible. If it is too hot or too cool and the eggs won’t develop properly. Later in the incubation process, proper temperature isn’t quite as important.  After a couple of weeks the falcons will be able to leave the eggs uncovered for longer periods of time.  Sometimes leaving the eggs uncovered frequently, or for long periods can mean that the eggs hatch a few days later than normal. This is a very well protected nest box in a location where the resident peregrines will not be disturbed, so they will tend to incubate steadily until the eggs hatch.

According to Derek Ratcliffe, the eggs of the peregrine falcon are among the most handsome laid by any species of bird!  He notes that the prevailing color is reddish-brown with a wide variation.  The surface of the fresh egg has variable amounts of bright red-brown markings appearing as a freckled, mottled, or blotched layer which can easily be rubbed off when the shell is wet. This non-fast layer of pigment gives a peregrine egg much of its beauty and richness, and in fresh specimens is often accompanies by a kind of bloom!

During the normal course of incubation, one of the adults is nearly always on the nest. Exceptions are during disturbance, for short periods on particularly warm days, or for a few minutes during food exchanges. The female does the majority of incubation. The male brings food to her several times daily, or sometimes simply relieves her and takes a turn on the eggs while the female eats, preens, and relaxes. When she returns to the nest box to relieve the male, he usually is waiting on the outer edge of the nest box. It is often a a challenge to identify the male from he female, as the male’s leg band is not always easy to see.  It will be helpful to identify field marks to distinguish the sexes.

Embryonic Development

Many questions have come in about exactly what happens during incubation, in terms of embryonic development.  It is a fascinating question and related to the very mystery of life, and how young peregrines develop inside the egg. So, what happens when?

Over the next number of days, we’ll look a bit closer at how the embryo develops.  Resources will include two book on avian embryonic development and an old blog, specifically about peregrine falcons, that includes a number of entries on this topic.

The age of the embryo when the egg is laid varies. Peregrines tend to lay eggs during the night or early morning or in the evening.; if the egg is not complete until later in the day, it will probably not be laid until the next day. The rate of development of the embryo once the egg is laid also varies. If the eggs are cooled after laying, development of the embryo ceases until the temperature rises again. Development can resume even after the eggs have been cooled for several days. The temperature of eggs incubated by their mother is 106 degrees Fahrenheit The temperature of course will vary when the peregrine leaves the eggs to eat, etc. All of this affects the rate at which the embryo develops and, therefore, how long it takes for the chick to hatch.

The first 4 days are essential. A lot is going on in those 4 days. Let’s have a closer look inside the eggshell. It is a magic journey through the universe of the dawning of life itself.

First Day: The Journey Begins

Before the Egg is Laid:

* The egg is fertilized.

* The zygote divides and begins to grow.

* The cells segregate into groups of specialized function.

* The embryo nearly stops growing between laying and incubation.

During Incubation:

* The area pellucida and area opaca of the blastoderm develop.


Second day:

*27 hours: The alimentary tract appears.

*28 hours: The brain crease begins to form.

*29 hours: Somites appear.

*31 hours: The brain and nervous system begin to form.

*32 hours: The head fold begins to form.

*34 hours: Blood islands appear.

*35 hours: The eyes begin to form.

*37 hours: The heart begins to form.

Third day

*52 hours: The ears begin to form.

*58 hours: The heart starts to beat

Fourth Day

*76 hours: head turns to the left

*78 hours: Amnion has enclosed the embryo

*80 hours: Allantois begins to form

*88 hours: The beak begins to form.

*92 hours: The leg begins to form.

*94 hours: The wings begin to form

Literature cited:

White, C. M., N. J. Clum, T. J. Cade and W. G. Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.

Ratcliffe, D. 1993. The Peregrine Falcon. 2nd ed. Carlton, England: T. and A. D. Poyser.

Cade, T. J., J. H. Enderson and J. Linthicum. 1996a. Guide to Management of Peregrine Falcons at the eyrie. Boise, ID: The Peregrine Fund, Inc. (Excerpt: Linthicum, Janet. Observing Breeding Behavior)

Veldhuis, Froona, Embryo: the first four days, Sept. 6, 2008,

Lawrence Peregrines: Egg #4!

March 28, 2020 in In the Nest Box

Conditions; clear skies, wind S at 3MPH, temp at 37F; forecast for day ahead – increasing clouds, with a high near 56. Calm wind becoming southeast 5 to 7 mph in the afternoon. Tonight rain likely, mainly after 3am. Cloudy, with a low around 40. Light southeast wind. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

2020.0328.LPWhat a joy to behold this morning just before 7AM….egg #4! The eggs have been laid 48 hours apart over last number of days.  This is the normal pattern and this may be the last egg to be laid. So now, the Peregrines shift into full and shared incubation duties that will last the next 32 to 33 days or so.  We are about a week ahead of last year’s egg laying time frame and two weeks ahead from two years ago.  With God’s grace the circle of life continues!

2020.0328.LP1According to Birds of North American Online: the eggs are fairly smooth without gloss. When fresh, ground color varies from pale creamy to brownish or reddish overlaid with dots, spots, and blotches of various warm browns to deep reds and purples; great variation. Generally deeper and richer color than other large North American falcons.

Lawrence Peregrines: Egg #3

March 26, 2020 in In the Nest Box

Conditions: partly sunny, wind N at 18MPh, with gusts to 29MPH, 40F; forecast for today – cloudy through mid morning, then gradual clearing, with a high near 45. North wind 11 to 16 mph, with gusts as high as 28 mph; tonight – increasing clouds, with a low around 40. Light south wind becoming southwest 10 to 15 mph in the evening. Winds could gust as high as 25 mph.

2020.0326.LP-001After a long observation period this morning through the New Balance Falcon Cam, finally just before 9AM, the female lifted up and took in flight for a break and revealed egg #3 right on schedule.  Typically the female Peregrine lays eggs about every 48 hours until the process is complete.  We have seen mostly 4 eggs laid per year at this location, and usually near the end of March! This first image shows the eggs in the scrape all close together!

2020.0326.LP1-001Moments later, the female returned to the lateral perch that extends out from the nest box.  She rested there for a awhile before resuming her incubation duties!

Lawrence Peregrines: 2020 Egg #2!

March 26, 2020 in In the Nest Box

Conditions: overcast skies, wind NW at 7MPH, temp at 35F; forecast for today – partly sunny, with a high near 51. Northwest wind around 8 mph and tonight -mostly cloudy, with a low around 33. Northeast wind 3 to 5 mph.


Great news this morning about 10 minutes before sunrise time, checked the nest box web cam and egg #2 has been laid overnight! This first image was captured through the webcam about 6:40AM. At first look, the female was out of the nest box, and then returned minutes later. Normally, the eggs are laid 48 hours apart, but there may be variations. We’ll expect the third egg on Thursday morning. Until the next to last egg is laid, the female may only incubate form time to time unless the temp is a bit cooler.



Later in the afternoon as the sun came out and the temperature warmed up, the female was seen incubating both eggs!

Lawrence Peregrines: 2020 Egg #1!

March 22, 2020 in In the Nest Box

It was a cold start to this Sunday, with temperatures in the upper teens to 20s, under a clear sky and subtle breeze.  This afternoon, under sun-filled skies, temperatures only rebounded back into the upper 30s. The wind chills were in the upper 20s through most of the day. Tonight, the Peregrines will have increasing clouds, with a low around 24. Southeast wind around 6 mph.

2020.0322.LPMade a visit to the extended Clock Tower area late Friday afternoon, and checked on the activity around the nest box and the extended Clock Tower. It was fairly quiet and the female was seen from the street and through the webcam. She was mulling around inside the nest box. Checked again this morning and wonderful surprise in seeing the first egg for 2020!

Later in the afternoon, she spent a more time incubating the egg, and basking in the later afternoon sunshine! Recently, her behavior was very consistent with the general lethargy that a female falcon typically experiences in the few days prior to laying the first egg. In many cases this lethargy may last a week or longer. She lazes around and spends lots of time in the nest box, nest scraping, and other courtship related activities.

2020.0322.1-001Incubation usually will not begin until the second to last egg has been laid. In this cool spring weather, with night time temps in the low 30’s, the female will spend some time incubating the egg, but it may not be a non-stop effort! The female has a silver federal leg band on her right leg; and a black over green 38/BV band on her left leg.  The male has only a silver right leg band and no band on his left leg.

Peregrine Falcons: Day 31

June 4, 2019 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

The Peregrines started off the day under fair skies, wind from the Sw at 6MPh, and  temp at 47F.  The day ahead calls for increasing clouds, with a high near 68. West wind 5 to 11 mph. Tonight, a chance of showers, mainly after 10pm. Cloudy, with a low around 54. West wind 5 to 9 mph becoming calm in the evening. 

2019.0604.2By day 31, the chicks often become actively interested in losing their down, preening themselves and sometimes ending up with feathers stuck to their beak as a result.  From the back they are looking increasingly dark, with the wing feathers approaching full length. In this photo, the chick in the back left corner was wing flapping, the others have been preening.  The darker feathers are coming in all over, and the down is decreasing rapidly!

Around this time, a nestling can rip up a prey item quite well, and at 39 days it soon demolishes even intact prey items. At this stage, prey is usually left intact for the young to deal with, though the parent may still break food up into smaller pieces.  There is, however, a considerable overlap between parental and self-feeding, and adults will present young with pieces of torn-up prey until they fledge, especially if nestlings solicit.

Literature cited:

Ratcliffe, D. 1993. The Peregrine Falcon. 2nd ed. Carlton, England: T. and A. D. Poyser.

The Canadian Peregrine Foundation, Peregrine Falcon Development – Age Guide;

Lawrence Peregrines: Day 30!

June 3, 2019 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

This morning the Peregrines started the day under fair skies, wind from the west at 6 MPH, and the temp at 55F.  The forecast calls for sunny skies, with a high near 68. West wind 6 to 11 mph increasing to 12 to 17 mph in the afternoon. Tonight, mostly cloudy during the early evening, then becoming clear, with a low around 47. West wind 6 to 13 mph, with gusts as high as 26 mph.

2019.0603.1It’s often around day 30 that the chicks seem to turn into “real” peregrines almost overnight, very rapidly losing much of the down on their breast, thus revealing the heavily streaked breast feathers they will be carrying for the next year. In this photo, the larger female chick had just been flapping and the darker feather colors, on the wings, back, and tail are very visible! Feather ruffling with body and head shaking is now marked and increasing time is spent in exercise, notably walking on the feet and wing-flapping.  The young are now better able to eject their droppings out of the nest box. They present their backs to the edge of the nest box, but are careful not to fall out, and have a fairly well developed sense of the gravitational hazard…..but sometimes, it is…….look out below!

Literature cited:

Ratcliffe, D. 1993. The Peregrine Falcon. 2nd ed. Carlton, England: T. and A. D. Poyser.

The Canadian Peregrine Foundation, Peregrine Falcon Development – Age Guide;