Saturday, April 14, 2012

Waiting for the first "pip"

If the weather folks are to be believed, this gorgeous Saturday morning in Philadelphia is the start of a spectacular few days.  The spring flowers are loving it -- the wisteria blooms on the porch of my house have never been lovelier or denser.

At the Franklin Institute hawk nest, incubation continues.  The parent hawks are on a really smooth routine, each taking turns sitting on the eggs.

Dad always looks a bit scrunched up and anxious.  His wings stay clenched on his back ...

... unlike the formel who lets her wings droop down her sides.


When the hawks switch off, the new "sitter" rolls the eggs.  Here's the formel getting the eggs just in the right spot ...

... to get them positioned on her brood patch, then she settles back down on them

She keeps an attentive eye on what is happening on the always-busy streetscape below.  Right now, the feather color is really smooth on her head...

... compared to dad's slightly streaked head

 Occasionally, the eggs are hawkless, and we can do a quick check to see if a pip has appeared yet on any of them.

A pip or tiny hole in the egg is the first indication that hatching is underway.  John Blakeman gave us some great information on pipping and hatching back in 2010, so let's do a review!  I added a couple of images by way of explanation, but these are not of hawk eggs or eyasses.
From John Blakeman:

"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.
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

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