3/17/17 – Happy St. Pip Day?

3/17/17 – Fans of the Hanover Bald Eagle‘s nest can celebrate this year’s St. Patrick’s Day with pip-watch! What is pip-watch? It is when people who watch nest cameras anxiously anticipate the coming pip, of course! What is a pip? Pip stands for ‘peep is pecking’ and it means an egg is beginning to hatch.

There are two forms of pip, the internal pip is when the chick breaks through the inner membrane, underneath the shell, and the chick can begin to breathe the air inside the shell. The external pip is when a small hole appears in the shell, and the chick can start to breathe air from outside the shell. The internal pip can occur 1-2 days before the external pip.

How do these pips occur? There are complex hormonal and chemical changes that occur that influence hatching, but simply put there are two main adaptations that assist the chick in hatching: the egg-tooth and the hatching-muscle.

The egg-tooth is a sharp projection on the top of the bird’s beak that breaks the inner membrane, and then the egg-tooth is scraped against the shell to create the hole that we can see in the shell. The egg-tooth falls off or is worn away within a few days after hatching. The hatching-muscle is a strong muscle on the back of the neck that helps the chick push its head back or up against the shell.

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Egg-tooth visible at the end of the beak. Photo credit: Raptor Resource Project.

These processes take time. Once the external pip occurs it can take up to a day or more for hatching to be complete. The chick’s body has to adjust to the physiological changes that take place when it goes from getting nutrition from the yolk to breathing air. The yolk is also resorbed in this time. The respiratory and circulatory system need to adjust to these changes. Some of this time is spent resting and recovering from the exertion of breaking out of the shell.

Vocalizations may also occur while the eaglet is still inside the shell. Eaglets can be heard 12 hours or more before the pip occurs. For some types of birds these vocalizations serve to synchronize hatching of the clutch.

Here is some more information about the anatomy inside an egg. If you would like to see a closer look at a pip, here is a video made from this season’s hatching at the Southwest Florida Eagle Cam.

There are always exceptions to the rule! Did you know that kiwi, and ‘megapodes’ like the Australian Brush-turkey and NewGuinea Scrubfowl, use their feet, instead of an egg-tooth, to break out of their shell?


3/14/17 – Hanover eagle covered in snow by nor-easter

3/14/17 – The nor-easter dumped enough snow on the Hanover nest to cover the female (again) as she incubates two eggs.

Hanover female covered in snow 3/14/17. Image courtesy of the Pennsylvania Game Commission and HD of Tap.

The female took her time coming out from under her snow blanket this morning. The eggs likely remained warm under the blanket of snow, as snow is a good insulator. Feathers are a wonderful insulator too, as evidenced by the fact that none of the snow melted off the back of the eagle. The trick over the next few days will not be keeping the eggs warm, but keeping them dry, as the snow melts. This time-lapse video shows the Hanover female uncovering her eggs briefly this morning. You can see the eggs, and the egg cup, appear to have remained dry. The female’s feathers under her body and legs appeared to be dry also. There are plenty of grasses and straw near the nest and I suspect we will be seeing new nest material brought in as the snow begins to melt.

That does not mean that there is no chance of nest failure, as the Pennsylvania Game Commission is studying the effects of severe winter storms on the nesting success of Bald Eagles. What can you do to help the eagles thrive through severe weather? Tell your politicians that you believe in science and understand the impact that high carbon emissions have on a changing climate. Support the use of ‘green-energy’ alternatives over the increased use of coal. Be aware though, no matter how much we curb greenhouse gas emissions today, it will take many years before an impact is felt, as the climate is expected to continue to warm due to emissions that have already occurred.

Hanover female buried in snow early morning 3/14/17. Image courtesy of the Pennsylvania Game Commission and HD on Tap.