The 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.

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.

MAJOR EVENTS

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, 

http://falcoperegrinus-froona.blogspot.com/2008/09/embryo-first-4-days.html

Another 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.

A 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!

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.

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)

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.

The 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.

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!

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

Onset Of Broodiness And Incubation In Relation To Laying

Here 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.

Incubation 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.

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.

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. https://doi.org/10.2173/bna.660