Lawrence Peregrines: brood patch

April 20, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0420.1-001The peregrines started Friday morning with overcast skies, wind from the west at 6MPH and the temp at 37F.  The forecast for the day ahead calls for partly sunny skies, with a high near 53. Northwest wind 9 to 14 mph, with gusts as high as 31 mph.  The next few days are looking much warmer….finally!  While taking a look just after 6:30 AM this morning, the female was incubating the eggs.  She started to wail, and it looked like she was wailing loudly.  She settled back down, and remained on the eggs for over an hour.  Then she popped up and went out for a quick flight, an then returned right away.  Keeping the eggs warm is a long, slow, and tedious process.

2018.0420.2-001So how is it that the peregrines provide constant heat to the eggs?  Many bird species, including peregrine falcons, have a special adaptation that helps them keep their eggs warm. The birds develop featherless areas on their breast called brood patches. These areas develop thickened skin and an increased blood flow that helps the birds pass body heat along to the developing embryos inside the eggs. Male peregrine falcons also develop brood patches and help with incubation, but as the female will do the majority of this work her brood patch is much more developed.

Literature cited: Richmond Falcon Cam, Brood Patches,   Virginia Department of Game and Inland Fisheries, P.O. Box 90778, Henrico, VA 23228-0778

Lawrence Peregrines: how incubation works?

April 19, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0419.1The peregrines started the day under overcast skies, wind west at 6MPH, and temp around 43F.  Today’s forecast calls rain and snow, becoming all rain after 11am. High near 45. Light and variable wind. Chance of precipitation is 80%. Total daytime snow accumulation of less than a half inch possible.  Snow…..AGAIN??

Had a chance to observe the nest box from just before 5:30 AM today and both adults were in and out of nest box a number of times.  The female raised up about 5:40 AM, made a nice stretch of wings and legs, and then departed in south bound direction.  Then, the two of them exchanged places a number time before the male finally settled in and remained on the eggs.

2018.0419.2So, just how does incubation work?

Heat makes the eggs start developing. When the eggs reach about 98.6°F, or 37°C the egg begins changing into an eyas, or young falcon. Conveniently enough, a peregrine’s natural body temperature is about 103°F, or 39.5°C, so to heat up the eggs all they need to do is to get some of that body heat onto the eggs. Now, a Peregrine’s feathers make very good insulation. That’s how they can stand to stay out in cold temperatures without freezing to death. But while those feathers keep the cold air away from the falcon’s skin, they also keep their body heat from getting out.

2018.0419.3So to incubate the eggs, the peregrine carefully settles down, shifting from side to side to get the eggs beneath their feathers. The male in Lawrence, tends to shift a lot while settling on to the eggs, while the female carefully settles down with minimum fuss. Falcons have brood patches, areas on their breasts with a lot of blood vessels close to the surface of their skin. The blood vessels concentrate their body heat, making it easier to transfer the heat to the eggs. Both adult peregrines have brood patches, though his are smaller than hers, which makes sense since he’s a smaller bird.  More on how to tell the difference between male and female in next post! 

Literature cited:  Imprints Blog, The Journal of the Rfalconcam, Rochester Falcon Cam.  The Genesee Valley Audubon Society is the local chapter of the National Audubon Society in Rochester, NY. GVAS sponsors the Rochester Falconcam (Rfalconcam) as part of their education and awareness programs.

Lawrence Peregrines: early embryo develops?

April 17, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0417.1-001The peregrines started the day with overcast skies, winds from SW at 13MPH and temp at 48F.  The forecast for today calls for mostly cloudy skies, with a high near 51F, west wind 7 to 11 mph, with gusts as high as 21 mph.

Had a look in just before 6AM and the male was incubating.  He took off in flight and returned a minutes later.  Again, he was very fidgety around the eggs, and hovered near and over eggs, but continued to behave in a tentative way.  The female returned and started wailing at him.  He departed and she settled right in over he eggs in motherly incubation mode.

2018.0417.2-001Many 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: Veldhuis, Froona, Embryo: the first four days, Sept. 6, 2008,

Lawrence Peregrines: female wailing at the male!

April 17, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Haverhill

It’s Marathon Monday in the extended Boston area, and the day is starting with light rain with fog and mist, strong winds blowing from the NE at 18MPH with gusts close to 30MPH, and the temperature at 37F.  For the peregrines, the west facing nest box is shielded from direct winds. 

The forecast calls for rain off and on throughout the day. Some of the storms could produce gusty winds and heavy rain. Patchy fog. High near 50. Breezy, with an east wind 16 to 20 mph, with gusts as high as 32 mph. New rainfall amounts between 1 and 2 inches possible.

2018.0416.3-001During incubation, an observer may spend lots of time watching very little activity.  The peregrines take turns brooding the eggs. Typically, the female incubates about 2/3 of the time, often for four or more hours before the male relieves her. Males brood for shorter periods– typically 2 to 3 hours, and they brood less frequently. While one adult is brooding, the other may be out hunting. Brooding falcons still need to eat, after all. If they’re not hunting, the other falcon usually stays close to the nest.  The photo on the left shows the female sitting on eggs quietly and with great comfort.  She will adjust as she needs to but is not fidgety as the male tends to be!

2018.0416.1Sometimes while the female is brooding the eggs, the male will bring her food that he has hunted. She’ll eat the food, sometimes inside, and other times, outside the nest box while he takes a turn incubating, but then she’ll come back and take over– provided she can get him to move off the eggs. If he doesn’t move right away, she may stand in the nest box and wail at him. Wailing has different meanings for falcons, but in general it indicates dissatisfaction with the current situation.  Here they are together, inside the nest box at around 10:35 AM today, and she is wailing on him big time.

2018.0416.2So if this female wails at her guy while he’s incubating, or in the nest box it’s her way of telling him she’s not happy that he’s still standing around, or sitting on the eggs. As with most other interactions between male and female peregrines, the female usually gets her way, though sometimes it takes a while for him to get the message!  Guess who’s walking away, with his head bowed low, after getting wailed at….the male….note right leg silver leg band.

Literature cited:  Imprints Blog, The Journal of the Rfalconcam, Rochester Falcon Cam.  The Genesee Valley Audubon Society is the local chapter of the National Audubon Society in Rochester, NY. GVAS sponsors the Rochester Falconcam (Rfalconcam) as part of their education and awareness programs.

Lawrence Peregrines: what happens during incubation?

April 15, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0415.1Another overcast morning in Lawrence with winds from NE at 13MPH, gusts up to 25MPH, and the temp at 35F, but a wind chill at 26F that makes it feel much cooler 35F.  Not looking to be such a nice day.  A least the wind is from the NE and that leaves the nest box well shielded from string direct wind.

The forecast calls for a chance of rain before 7am, then rain likely, possibly mixed with freezing rain between 7am and 8am, then sleet likely after 8am. Cloudy, with a high near 32. Northeast wind 10 to 13 mph, with gusts as high as 26 mph. Chance of precipitation is 70%. Little or no sleet accumulation expected.

2018.0415.2A number of times today, the eggs were left alone for longer stretches of time than is normal.  Did not observe a changing of the guard between male and female!




2018.0415.3During 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.


Literature Cited:

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)

Lawrence Peregrines: very handsome eggs!

April 14, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

Saturday morning started off with clear skies and bright sun, with a bit of haze.  During the morning the skies turned partly cloudy and then completely overcast.  The wind started out from the north at 8MPH, and then shifted around to the east, but remained around the same speed until picking up speed late in the day.  The temp hovered around 50F most of the day.

2018.0414.1The peregrines spent most of the day in incubation mode.  Some times, you have to watch for quite a while until you observe a break in the action!  It is fascinating to watch how careful they are when hovering over and then settling onto the eggs.  Frequently, you will be able to watch a nervous twitching and jiggling around until the incubating bird gets it just right.



2018.0414.2According 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!



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

Lawrence Peregrines: full time incubation begins!

April 13, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

Onset Of Broodiness And Incubation In Relation To Laying

2018.0413.1Here is a look around 6:30 AM this morning, under clear skies, winds from the west at 8MPH, and temps in the low fifties. It looks like we have officially started full time incubation. In temperate latitudes, full time incubation usually begins with the penultimate, or second to last egg egg.  When temperatures are at or near freezing, active incubation may start a bit earlier. We have now seen either the female or the male incubating the eggs with almost no break in between shifts, since the fourth egg was laid.  The male seems to be taking a very active role in the incubation process.

2018.0413.2Incubation Patches

Both 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.

2018.0413.3Incubation 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.

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.

Lawrence Peregrines: Fourth egg!!

April 12, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0412Great news….the fourth egg was laid overnight and now the full-time incubation process begins and lasts about 30 days!  This is likely the final egg, but were not able to know for sure just yet.

Checked in a look around 6AM this morning and the female was hunkered down, in incubation mode, under partly cloudy skies, winds from the south at 6MPH, and temp at 35F.

The forecast today calls for a chance of showers, mainly after 5pm. Increasing clouds, with a high near 58. Calm wind becoming southwest 5 to 8 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.  Finally, warmer temps on the way!

2018.0412.1The male came in and allowed the female to take a break, and then he proceeded to incubate the eggs, now starting to share in the task of sharing the duties.  Once incubation begins, the incubation process usually takes between 29 – 33 days until the chicks hatch!  During this time the weather is expected to become warmer!  Despite the dramatic events of the last two weeks, the circle of life continues on!

Lawrence Peregrines: awaiting next egg?

April 11, 2018 in In the Nest Box, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0411.1-001Up again just before 6AM, and observed the female out of the box, and 3 eggs nestled close to one another, under overcast skies, fog and mist, little wind, and temp at 34F. A dense fog advisory is in effect for a few more hours.  The female will typically get and head out first thing in morning.  Once full time incubation starts, the male will cover for her while she is out. 

The forecast calls for patchy fog before 9am. Otherwise, partly sunny, with a high near 47. Calm wind becoming southwest around 5 mph in the afternoon.

2018.0411.2-001A 6:18 AM, the male arrives at the nest box, the female departs, and the male fidgets around, adjusting eggs a bit, and then departs after 7 minutes leaving the eggs unattended.  This would suggest that full time incubation has not yet started.  Full time incubation means one of the falcons will be on the eggs at all times except for a few short breaks, typically lasting no more than 2-3 minutes.  The male was almost fumbling and bumbling with the eggs and seemed unsure on what to do….stay tuned!

2018.0411.3-001The female returns at 6:36 AM and lands on the outer edge of the nest box.  She moves around just a bit and then resumes her incubation posture. She will often make a number of micro adjustments before sitting still for a while. The eggs were left alone for almost 20 minutes.


Lawrence Peregrines: Three eggs!!

April 10, 2018 in In the Nest Box, lawrence peregrines, Peregrine Falcons Eastern Massachusetts, Peregrine Falcons Massachusetts

2018.0410.1-001Up early just before 6AM, for a look at the possible third egg and the answer is YES!  This morning the female is waking up to overcast skies, wind from the NE at 5MPH, and temp about 34F.

The forecast for today: Scattered showers, mainly after noon. Mostly cloudy, with a high near 47. Calm wind becoming south around 6 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.


The female was moving around quite a bit late yesterday afternoon, and spent time standing over the two eggs.  It looked like she was ready to drop the third egg, but the timing was not yet right.  Looks like the third egg was laid after dark.  The time interval between egg #2 and egg #3 looks to be in the range of 56 -64 hours, or just a bit more than 2 days apart……well within normal range!

2018.0410.2Around 6:25AM the female departed for another break, and then returned and perched on the outer pole for a while, before returning to the inside of the box…




2018.0410.3Once again, she hovers over the eggs, and then nestles in back in incubation mode to keep the eggs warm.  The male has not yet engaged in incubation duties, but will do so shortly!