Sunday, April 18, 2010

What lies ahead with the hatching

If all goes well, we should soon start to see the eggs hatching. Here is some knowledgeable commentary from John Blakeman about what we will be seeing. I have added a couple of images by way of explanation, but these are not of hawk eggs or eyasses.

From John Blakeman:

"It would be well for everyone to ponder what’s now ahead.

We all expect just a wonderful experience as we witness the hatching, with the first indication being that pipping has begun. Pipping is when the little eyass inside the egg begins to thrust its beak out at the end of the egg and will create a small crack. That’s pipping, the cracking of the egg, and it’s very important.

It’s done by the "egg tooth," a slight temporary projection on the top of the beak.

With a rounded bill, it would be otherwise very hard for the little eyass to poke any sort of hole through the egg shell. But the slightly pointed egg tooth will allow the weak eyass to accomplish this.

That will be the first sign of hatching. Someone will see the slightest crack on the end of an egg. Everyone will get understandably excited.

But then disappointment will set in. We would all expect the little eyass to continue to break open the entire egg after the first pipping and step right out into the world. But it doesn’t (and shouldn’t) happen that way.

After pipping, the little eyass stops pecking at the egg shell and remains rather quiet. (Wish we had a microphone buried in the nest so we could hear all of this.) The eyass is quiet for two reasons. First, she has used a lot of energy punching her beak out at the egg, so she tires of all this activity. But more importantly, her lungs are not ready to be exposed quickly to open, dry air.

For most of a month, her lungs have been filled with fluids, and she’s been breathing very moderately through simple air diffusion into her body tissues. But in the last week or so, things start drying out inside the egg and slowly her lungs will get filled with the gases in the end of the shell. It’s still 100% humidity in there, and all is well.

But after pipping, dry air from the outside begins to replace the moist air inside the egg. If that happens too fast because the pipping creates an overly opening, the lungs dry out too rapidly and the eyass simply dies from non-functioning lungs.

So, we must be patient when we see the first pipping. It could be a day or longer before the eyass finally emerges. There is no need for the little hawk to get out of the egg. She’s happy with the humid air in there, while her lungs start to adjust to cold, dry air on the outside.

At the end, when she’s ready, the eyass will make some final thrusts with her head and create an opening big enough from which to emerge. She will hardly be able to hold up her head, and she may not eat or be fed for up to a day. It can be so frustrating to see the little hawk lying down in the nest, without the energy to even stand up and open its mouth for the tiny tidbits of food the formel will offer when the eyass first takes this "I’m hungry" posture.

We just have to wait for all of this to happen. To rush any of this would be to endanger the health of the eyass. In captive breeding of raptors, falconers know that they must never help the little eyass get out of the egg too soon. The eyass instinctively knows what to do, and when to do it. We must merely stand back and watch this marvelous sequence of behaviors.

And we need to continue to thank The Franklin Institute for allowing us to watch all of this. We raptor biologists can never see any of this when aiming our spotting scopes at wild nests. It’s all way up there in a tree, and we can see only the haggards coming and going. Here at the Franklin Institute, everyone gets to look right down inside the nest and see it all. And once again, we should get to see some pipping and then hatching, followed by the formel feeding the newly-emerged downy eyasses.

But I offer a sobering thought, one that we must consider and be gravely ready to confront. As good as these haggards have been, there can be no guarantee that all three eggs will pip, hatch, or have their eyasses grow up and fledge. The stark reality is that one or more eyasses may fail to hatch, or fail to thrive and die. I hope this doesn’t happen. It didn’t last year, so there is an increased chance of full success this year, too.

But eyass deaths are rather common. It’s just part of nature. Should an egg fail to hatch, or a little eyass dies, we must accept this as a natural part of the entire process.

Now, let’s sit back and wait, with our eyes glued to the screen. Let new red-tail eyasses grace the skies of Philadelphia once again!"

–John Blakeman


  1. Excellent information Sunny, and John!! Perfect timing to post this, thank you both!


  2. Thanks so much to you and to John. I so appreciate this information. ~Lynk

  3. Thanx so much for this wonderful blog and information. Did i just see one of the eggs start to hatch! or am i dreaming?!? very exciting.

  4. Hi John,

    Now that my free ebook on the American Crow is published at I am starting another free ebook on the Chipping Sparrow. I would like permission to use the image of the fresh Red-tailed Hawk nestling showing its egg tooth. Thanks
    Tom Reaume, Winnipeg, Manitoba